Changelog of @hackage/futhark 0.25.15

Changelog

All notable changes to this project will be documented in this file.

The format is based on Keep a Changelog and this project adheres to Semantic Versioning.

[0.25.15]

Added

Incremental Flattening generates fewer redundant code versions.
Better simplification of slices. (#2125)

Fixed

Ignore type suffixes when unifying expressions (#2124).
In the C API, opaque types that correspond to an array of an opaque type are now once again named futhark_opaque_arr_....
cuda backend did not correctly profile CPU-to-GPU scalar copies.

[0.25.14]

Added

The prelude definition of filter is now more memory efficient, particularly when the output is much smaller than the input. (#2109)
New configuration for GPU backends: futhark_context_config_set_unified_memory, also available on executables as --unified-memory.
The "raw" API functions now do something potentially useful, but are still considered experimental.
futhark --version now reports GHC version.

Fixed

Incorrect type checking of let-bound sizes occurring multiple times in pattern. (#2103).
A concatenation simplification would sometimes mess up sizes. (#2104)
Bug related to monomorphisation of polymorphic local functions (#2106).
Rare crash in short circuiting.
Referencing an unbound type parameter could crash the type checker (#2113, #2114).
Futhark now works with GHC 9.8 (#2105).

[0.25.13]

Added

Incremental flattening of map-scan compositions with nested parallelism (similar to the logic for map-reduce compositions that we have had for years).
futhark script, for running FutharkScript expressions from the command line.
futhark repl now prints out a message when it ignores a breakpoint during initialisation. (#2098)

Fixed

Flattening of scatter with multi-dimensional elements (#2089).
Some instances of not-actually-irregular allocations were mistakenly interpreted as irregular. Fixing this was a dividend of the memory representation simplifications of 0.25.12.
Obscure issue related to expansion of shared memory allocations (#2092).
A crash in alias checking under some rare circumstances (#2096).
Mishandling of existential sizes for top level constants. (#2099)
Compiler crash when generating code for copying nothing at all. (#2100)

[0.25.12]

Added

f16.copysign, f32.copysign, f64.copysign.
Trailing commas are now allowed for all syntactical elements that involve comma-separation. (#2068)
The C API now allows destruction and construction of sum types (with some caveats). (#2074)
An overall reduction in memory copies, through simplifying the internal representation.

Fixed

C API would define distinct entry point types for Futhark types that differed only in naming of sizes (#2080).
== and != on sum types with array payloads. Constructing them is now a bit slower, though. (#2081)
Somewhat obscure simplification error caused by neglecting to update metadata when removing dead scatter outputs.
Compiler crash due to the type checker forgetting to respect the explicitly ascribed non-consuming diet of loop parameters (#2067).
Size inference did incomplete level/scope checking, which could result in circular sizes, which usually manifested as the type checker going into an infinite loop (#2073).
The OpenCL backend now more gracefully handles lack of platform.

[0.25.11]

Added

New prelude function: manifest. For doing subtle things to memory.
The GPU backends now handle up to 20 operators in a single fused reduction.
CUDA/HIP terminology for GPU concepts (e.g. "thread block") is now used in all public interfaces. The OpenCL names are still supported for backwards compatibility.
More fusion across array slicing.

Fixed

Compatibility with CUDA versions prior than 12.

[0.25.10]

Added

Faster non-commutative reductions in the GPU backends. Work by Anders Holst and Christian Påbøl Jacobsen.

Fixed

Interpreter crash for certain complicated size expressions involving internal bindings (#2053).
Incorrect type checking of let binding with explicit size quantification, where size appears in type of body (#2048).
GPU code generation for non-commutative non-segmented reductions with array operands (#2051).
Histogram with non-vectorised reduction operators (#2056). (But it is probably not a good idea to write such programs.)
Futhark's LSP server should work better with Eglot.
Incorrect copy removal inside histograms could cause compiler error (#2058).
CUDA backend now correctly queries for available shared memory, which affects performance (hopefully positively).
futhark literate now switches to the directory containing the .fut file before executing its contents. This fixes accessing files through relative paths.

[0.25.9]

Added

The cuda and hip backends now generate faster code for scans that have been fused with maps that internally produce arrays. Work by Anders Holst and Christian Påbøl Jacobsen.
f16.ldexp, f32.ldexp, f64.ldexp, corresponding to the functions in the C math library.

Fixed

Incorrect data dependency information for scatter and vjp could cause invalid simplification.
Barrier divergence in certain complicated kernels that contain both bounds checks and intragroup scans.

[0.25.8]

Added

FutharkScript now has a $loadbytes builtin function for reading arbitrary bytes into Futhark programs.
futhark profile can now process reports produced by the C API function futhark_context_report().
futhark profile now also produces a timeline of events.

Fixed

futhark literate no longer fails if the final line is a directive without a trailing newline.
Parser now allows arbitrary patterns in function parameters and let bindings, although the type checker will reject any that are refutable (#2017).
Avoid generating invalid code in cases where deduplicated sum types are exposed through entry points (#1960).
A bug in data dependency analysis for histogram operations would mistakenly classify some loop parameters as redundant, leaving to code being removed.

[0.25.7]

Added

futhark autotune now supports hip backend.
Better parallelisation of scatter when the target is multidimensional (#2035).

Fixed

Very large iotas now work.
Lambda lifting in while conditions (#2038).
Size expressions in local function parameters had an interesting interaction with defunctionalisation (#2040).
The store command in server executables did not properly synchronise when storing opaque values, which would lead to use-after-free errors.

[0.25.6]

Added

The various C API functions that accept strings now perform a copy, meaning the caller does not have to keep the strings alive.
Slightly better lexer error messages.
Fusion across slicing is now possible in some cases.
New tool: futhark profile.

Fixed

Inefficient locking for certain segmented histograms (#2024).

[0.25.5]

Added

futhark repl now has a :format command. Work by Dominic Kennedy.

Fixed

Textual floating-point numbers printed by executables now always print enough digits to not hide information. Binary output is unchanged.
Invalid CSE on constants could crash the compiler (#2021).

[0.25.4]

Fixed

Invalid simplification (#2015).
Rarely occurring deadlock for fused map-scan compositions in CUDA backend, when a bounds check failed in the map function.
Compiler and interpreter crash for tricky interactions of abstract types and sizes (#2016). Solved by banning such uses - in principle this could break code.
Incomplete alias tracking could cause removal of necessary copies, leading to compiler crash (#2018).

[0.25.3]

Added

pyopencl backend: compatibility with future versions of PyOpenCL.
New backend: hip.

Fixed

Exotic problems related to intra-group reductions with array operands. (Very rare in real code, although sometimes generated by AD.)
Interpreter issue related to sizes in modules (#1992, #1993, #2002).
Incorrect insertion of size arguments in in complex cases (#1998).
Incorrect handling of match in lambda lifting (#2000).
Regression in checking of consumption (#2007).
Error in type checking of horisontally fused scatters could crash the compiler (#2009).
Size-polymorphic value bindings with existential sizes are now rejected by type checker (#1993).
Single pass scans with complicated fused map functions were insufficiently memory-expanded (#2023).
Invalid short circuiting (#2013).

[0.25.2]

Added

Flattening/unflattening as the final operation in an entry point no longer forces a copy.
The opencl backend no longer always fails on platforms that do not support 64-bit integer atomics, although it will still fail if the program needs them.
Various performance improvements to the compiler itself; particularly the frontend. It should be moderately faster.

Fixed

Code generation for f16 literals in CUDA backend (#1979).
Branches that return arrays differing in sign of their stride (#1984).

[0.25.1]

Added

Arbitrary expressions of type i64 are now allowed as sizes. Work by Lubin Bailly.
New prelude function resize.

Removed

The prelude functions concat_to and flatten_to. They are often not necessary now, and otherwise resize is available.

Changed

The prelude functions flatten and unflatten (and their multidimensional variants), as well as split, now have more precise types.
Local and anonymous (lambda) functions that must return unique results (because they are passed to a higher order function that requires this) must now have an explicit return type ascription that declares this, using *. This is very rare (in practice unobserved) in real programs.

Fixed

futhark doc produced some invalid links.
flatten did not properly check for claimed negative array sizes.
Type checker crash on some ill-typed programs (#1926).
Some soundness bugs in memory short circuiting (#1927, #1930).
Another compiler crash in block tiling (#1933, #1940).
Global arrays with size parameters no longer have aliases.
futhark eval no longer crashes on ambiguously typed expressions (#1946).
A code motion pass was ignorant of consumption constraints, leading to compiler crash (#1947).
Type checker could get confused and think unknown sizes were available when they really weren't (#1950).
Some index optimisations removed certificates (#1952).
GPU backends can now transpose arrays whose size does not fit in a 32-bit integer (#1953).
Bug in alias checking for the core language type checker (#1949). Actually (finally) a proper fix of #803.
Defunctionalisation duplicates less code (#1968).

[0.24.3]

Fixed

Certain cases of noninlined functions in multicore backend.
Defunctionalisation of match where the constructors carry functions (#1917).
Shape coercions involving sum types (#1918). This required tightening the rules a little bit, so some coercions involving anonymous sizes may now be rejected. Add expected sizes as needed.
Defunctionalisation somtimes forgot about sizes bound at top level (#1920).

[0.24.2]

Added

futhark literate (and FutharkScript in general) is now able to do a bit of type-coercion of constants.

Fixed

Accumulators (produced by AD) had defective code generation for intra-group GPU kernel versions. (#1895)
The header file generated by --library contained a prototype for an undefined function. (#1896)
Crashing bug in LSP caused by stray undefined (#1907).
Missing check for anonymous sizes in type abbreviations (#1903).
Defunctionalisation crashed on projection of holes.
Loop optimisation would sometimes remove holes.
A potential barrier divergence for certain GPU kernels that fail bounds checking.
A potential infinite loop when looking up aliases (#1915).
futhark literate: less extraneous whitespace.

[0.24.1]

Added

The manifest file now lists which tuning parameters are relevant for each entry point. (#1884)
A command tuning_params has been added to the server protocol.

Changed

If part of a function parameter is marked as consuming ("unique"), the entire parameter is now marked as consuming.

Fixed

A somewhat obscure simplification rule could mess up use of memory.
Corner case optimisation for mapping over iota (#1874).
AD for certain combinations of map and indexing (#1878).
Barrier divergence in generated code in some exotic cases (#1883).
Handling of higher-order holes (#1885).

[0.23.1]

Added

f16.log1p/f32.log1p/f64.log1p by nbos (#1820).
Better syntax errors for invalid use of !.
futhark literate now supports a $loadaudio builtin function for loading audio to Futhark programs (#1829).
You can now mix consumption and higher-order terms in slightly more cases (#1836).
futhark pkg now invokes Git directly rather than scraping GitHub/GitLab. This means package paths can now refer to any Git repository, as long as git clone works. In particular, you can use private and self-hosted repositories.
Significant reduction in compilation time by doing internal sanity checks in separate thread.
New command: futhark eval. Evaluates Futhark expressions provided as command line arguments, optionally allowing a file import (#1408).
script input now allows the use of $loaddata.
Datasets used in futhark test and futhark bench can now be named (#1859).
New command futhark benchcmp by William Due.

Changed

The C API function futhark_context_new_with_command_queue() for the OpenCL backend has been replaced with a configuration setting futhark_context_config_set_command_queue().

Fixed

Minor parser regression that mostly affects the REPL (#1822).
Parser did not recognise custom infix operators that did not have a builtin operator as prefix (#1824).
GPU backends: expansion of irregular nested allocations involving consumption (#1837, #1838).
CLI executables now handle entry points with names that are not valid C identifiers (#1841).
Various oversights in the type checking of uniqueness annotations for higher-order functions (#1842).
Invalid short-circuiting could cause compiler crashes (#1843).
Defunctionalisation could mess up sum types, leading to invalid code generation by internalisation, leading to a compiler crash (#1847).
The #[break] attribute now provides the right environment to futhark repl, allowing local variables to be inspected.
Simplification of concatenations (#1851).
Array payloads in sum types no longer need parens (#1853).
When a file is loaded with futhark repl, local declarations are now available.
Missing alias propagation when pattern matching incompletely known sum types (#1855).
reduce_by_index and hist were in some cases unable to handle input sizes that do not fit in a 32-bit integer.
A fusion bug related to fusing across transpositions could result in a compiler crash (#1858).

[0.22.7]

Added

futhark literate now supports an :audio directive for producing audio files from arrays of i8 (#1810).
futhark multicore now parallelises copies (#1799).
futhark multicore now uses an allocator that better handles large allocations (#1768).

Fixed

Some record field names could cause generation of invalid C API names (#1806).
Memory block merging was extremely and unnecessarily slow for programs with many entry points.
Simplification mistake could lead to out-of-bounds reads (#1808).
futhark lsp now handles some bookkeeping messages sent by Eglot.
Parser can now handle arbitrarily complex chaining of indexing and projection.
Detect and complain about source files without .fut extension (#1813).
Overly conservative checking of whether a function parameter is allowed by be consumed - it was disallowed if it contained any scalars (#1816).

[0.22.6]

Added

Slightly better type errors for sum types (#1792).
Better tracing output in interpreter (#1795).
Improved optimisation of code that uses zero-element arrays (sometimes used for type witnesses).

Fixed

Mishandling of bounds checks in parallel backends could cause compiler crashes (#1791).
Mis-simplification of certain sequentialised scatters into single-element arrays (#1793).
Invalid scatter fusion would cause an internal compiler error (#1794).
The code generator flipped the order of match cases.
Simpification of concatenations (#1796).
Defunctionalisation error for fancy size programming (#1798).
Code generation for load-unbalanced reductions in multicore backend (#1800).
Futhark now works on CUDA 12 (#1801).
mul_hi and mad_hi for signed integer types now actually do signed multiplication (previously it was always unsigned).

[0.22.5]

Added

Memory short circuiting now also applied to the multicore backend.
Fixes for AD of scan with nonscalar operators. Work by Lotte Bruun and Ulrik Larsen.
Generalised histograms now supported in AD. Work by Lotte Bruun and Ulrik Larsen.
OpenCL kernels now embed group size information, which can potentially be used for better register allocation by the OpenCL implementation.

Fixed

A hole in the type checker that allowed one to sneak functions out of conditionals (#1787).
futhark repl: unsigned integers are now printed correctly.
A bug in the type-checking of match (#1783).
Missing sequencing in type-checking of in-place let expressions (#1786).
Crash in defunctionaliser caused by duplicate parameter names (#1780).
Infelicities in multicore codegen for scans (#1777).

[0.22.4]

Added

Memory short circuiting, a major new optimisation by Philip Munksgaard that avoids copies by constructing values in-place.

Fixed

assert was sometimes optimised away by CSE.
futhark literate now handles type abbreviations in entry points (#1750).
Handling of non-inlined functions in GPU code. Still very restricted.
Uniqueness checking bug (#1751).
Simplification bug (#1753).
A bug related to optimisation of scalar code migrated to GPU.
Memory optimisation bug for top-level constants (#1755).
Handling of holes in defunctionalisation (again).
A few cases where optimisation (safely but perhaps confusingly) removed bounds checks (#1758).
Futhark now works on Windows again (#1734). This support remains very flaky and not well tested.
Type inference of field projection (#1762).

[0.22.3]

Fixed

Non-server executables neglected to synchronise before printing results (#1731).
Fixed handling of holes in defunctionalisation (#1738).
Ascription of higher-order modules (#1741).
Fixed compiler crash when attempting to tile irregular parallelism (#1739).
Incorrect regularity checking in loop interchange (#1744).
Pattern match exhaustiveness of bools (#1748).
Improper consumption checking of nonlocal bindings (#1749).

[0.22.2]

Added

futhark repl is now delightfully more colourful.
futhark repl no longer prints scalar types with type suffixes (#1724).
futhark pyopencl executables now accept --build-option.
New functions: f16.nextafter, f32.nextafter, f64.nextafter, matching the ones in the C math library.
futhark literate now prints directives in the output exactly as they appear in the source.

Fixed

Diagnostics will no longer contain control codes when output is a file.
CLI executables now fail when printing an opaque instead of producing garbage. This improves handling of some incorrect uses of auto output (#1251).

[0.22.1]

Removed

Removed prelude functions reduce_stream, map_stream, reduce_stream_per, and reduce_map_per.

Fixed

Various fixes to scalar migration (#1721).

[0.21.15]

Fixed

Corrupted OOM error messages.
Excessive internal fragmentation for some programs (#1715).

[0.21.14]

Fixed

replicate was broken for sizes that didn't fit in i32.
Transposition of empty arrays in interpreter (#1700).
Exotic simplification error (#1309).
Rare race condition could lead to leaking of error message memory in multicore and ispc backends (#1709).
Overzealous aliasing for built-in overloaded types (#1711).

[0.21.13]

Added

New fusion engine by Amar Topalovic and Walter Restelli-Nielsen. Fuses more, which is good for some programs and bad for others. Most programs see no change. This is mainly a robust foundation for further improvements.
New experimental backend: ispc. By Louis Marott Normann, Kristoffer August Kortbæk, William Pema Norbu Holmes Malling, and Oliver Bak Kjersgaard Petersen.
New prelude functions: hist, spread. These function as non-consuming variants of reduce_by_index and scatter.
Using == to compare arrays is now deprecated.
New command: futhark tokens. You probably don't care about this one.
In the C API, opaque types that correspond to tuples or records can now have their elements inspected and be created from elements (#1568).
New server protocol commands: types, fields, entry_points.
Tuples and records can now be passed from FutharkScript to Futhark entry points (#1684).

Fixed

Sometimes missing cases in match expressions were not detected.
A defective simplification rule could in very rare cases lead to infinite recursion in the compiler (#1685).
Some broken links in futhark doc output (#1686).
Incorrect checking of whether a function parameter is consumable based on its type (#1687).
Missing aliases for functions that return multiple aliased values (#1690).
new/values functions for GPU backends are now properly asynchronous (#1664). This may uncover bugs in application code.

[0.21.12]

Added

Somewhat simplified the handling of "uniqueness types" (which is a term we are moving away from). You should never see * in non-function types, and they are better thought of as effect indicators.
futhark literate: prints tracing output (and other logging messages that may occur) when run with -v (#1678).
Entry points can now be any valid Futhark identifier.

Fixed

futhark test -C was broken.
futhark_context_free() for the GPU backends neglected to free some memory used for internal bookkeeping, which could lead to memory leaks for processes that repeatedly create and destroy contexts (#1676).
FutharkScript now allows ' in names.
futhark lsp now handles warnings in programs that also have errors.

[0.21.11]

Added

The CUDA backend now supports compute capability 8.6 and 8.7.
Philip Børgesen has implemented a new optimisation for GPU backends that migrates scalar work to the GPU, in order to reduce synchronisation. This results in major speedup for some programs.
String literals are now allowed in input blocks.
Experimental and undocumented support for automatic differentiation, available on the secret menu.
Assertions and attributes are now ignored when used as size expressions. E.g. iota (assert p n) 0 now has size n.
futhark test only runs the interpreter if passed -i.
futhark literate now shows progress bars when run with -v.

Fixed

futhark lsp is now better at handling multiple files (#1647).
Incorrect handling of local quantification when determining type equivalence in during module type ascription (#1648).
Incorrect checking of liftedness when instantiating polymorphic functions during module type ascription.
Tightened some restrictions on the use of existential sizes that could otherwise lead to compiler crashes (#1650). This restriction is perhaps a bit too might and it may be possible to loosen it in the future.
Another defunctorisation bug (#1653). Somehow we find these every time Martin Elsman writes a nontrivial Futhark program.
futhark bench: convergence phase now does at least --runs runs.
Errors and warnings no longer awkwardly mixed together in console output.
Slightly better type errors for ambiguous sizes (#1661).
Better type errors for module ascription involving nested modules (#1660).
futhark doc: some formatting bugs.
futhark doc didn't notice all local module types (#1666).
Missing consumption check in optimisation could lead to ICE (#1669).

[0.21.10]

Added

New math functions: f16.erf, f32.erf, f64.erf.
New math functions: f16.erfc, f32.erfc, f64.erfc.
New math functions: f16.cbrt, f32.cbrt, f64.cbrt.

Fixed

Variables being indexed now have correct source spans in AST.
futhark lsps hover information now contains proper range information.
futhark query and futhark lsp incorrectly thought size parameters had type i32.
futhark doc put documentation for prelude modules in the wrong location (which also led to messed-up style sheets).

[0.21.9]

Added

Sun Haoran has implemented unnamed typed holes, with syntax ???.
Sun Haoran has implemented the beginnings of a language server: futhark lsp. A VSCode language extension is available on the marketplace, but the language server should work with any editor.
Crucial new command: futhark thanks.
The GPU backends now support a caching mechanism for JIT-compiled code, significantly improving startup times. Use the futhark_context_config_set_cache_file() in the C API, the --cache-file option on executables, or the --cache-extension option on futhark test and futhark bench. These also work for the non-GPU backends, but currently have no effect. (#1614)
Aleksander Junge has improved futhark bench such that it intelligently chooses how many runs to perform (#1335).

Fixed

Incomplete simplification would cause some instances of nested parallelism to require irregular allocations (#1610).
Missing alias checking for a simplification rule related to in-place updates (#1615, #1628).
Incorrect code generation for certain copies of transposed arrays (#1627).
Fusion would mistakenly try to treat some loops with irregular sizes (#1631).
Memory annotation bug for non-inlined functions (#1634).

[0.21.8]

Added

Slightly better parse errors (again).
futhark literate now supports a file: option in :img and :video directives (#1491).

Fixed

Improved hoisting of size computations. This could cause some regular nested parallel programs to run into compiler limitations, as if they were irregular.
Rare code generation bug for histograms (#1609).

[0.21.7]

Added

futhark check-syntax: check syntactic validity of a program file, without type-checking.
Parsing multi-file programs is now parallelised, making it slightly faster.
Reloading a large program in futhark repl is now faster, as long as not too many of its files have been modified (#1597).

Fixed

Mistake in occurs check could cause infinite loop in type checker for programs with type errors (#1599).

[0.21.6]

Added

futhark bench now explicitly notes when a tuning file is not present.
futhark bench, futhark test and friends are now better at handling fatally terminating programs (e.g. segmentation faults).
Generated C code is now a lot smaller for large programs, as error recovery has been more centralised (#1584).

Fixed

Some bugs in checking for local memory capacity for particularly exotic generated code.
Insufficient hoisting of allocation sizes led to problems with memory expansion in rare cases (#1579).
Conversion of floating-point NaNs and infinities to integers now well defined (produces zero) (#1586).
Better handling of OOM for certain short-lived CPU-side allocations (#1585).

[0.21.5]

Added

API functions now return more precise error codes in some cases.
Out-of-memory errors contain more information.

Fixed

Yet another in-place lowering issue (#1569).
Removed unnecessary bounds checks in register tiling, giving about 1.8x speedup on e.g. matrix multiplication on newer NVIDIA GPUs.
A parser bug erroneously demanded whitespace in some type expressions (#1573).
Some memory was not being freed correctly when shutting down OpenCL and CUDA contexts, which could lead to memory leaks in processes that created and freed many contexts.
An incorrect copy-removal in some exotic cases (#1572).
'restore'-functions might perform undefined pointer arithmetic when passed garbage.

[0.21.4]

Fixed

A size inference bug in type checking of loops (#1565).
Exotic flattening bug (#1563).
Segmented reduce_by_index with fairly small histogram size would use vastly more memory than needed.

[0.21.3]

Added

Parse errors now list possible expected tokens.
Lexer errors now mention the file.

Fixed

Overloaded number literals cannot be sum types (#1557).
Defective GPU code generation for vectorised non-commutative operatators (#1559).
Excessive memory usage for some programs (#1325).

[0.21.2]

Added

New functions: reduce_by_index_2d, reduce_by_index_3d.
Manifests now contain compiler version information.

Fixed

Allocation insertion pass bug (#1546).
An exotic bug involving TLS and dynamically loading code generated by the multicore backend.
Unconstrained ambiguous types now default to () (#1552). This should essentially never have any observable impact, except that more programs will type check.
Double buffering compiler crash (#1553).

[0.21.1]

Added

Top-level value definitions can (and should) now be declared with with def, although let still works.
New tool: futhark defs, for printing locations of top-level definitions.

Changed

def is now a reserved word.

Fixed

Contrived intra-group code versions with no actual parallelism would be given a group size of zero (#1524).

[0.20.8]

Added

futhark repl now allows Ctrl-c to interrupt execution.

Fixed

Alias tracking of sum types.
Proper checking that a function declared to return a unique-typed value actually does so.
Faulty uniqueness checking and inference for lambdas (#1535).
Monomorphisation would duplicate functions under rare circumstances (#1537).
Interpreter didn't check that the arguments passed to unflatten made sense (#1539).
futhark literate now supports a $loaddata builtin function for passing datasets to Futhark programs.

[0.20.7]

Added

Better exploitation of parallelism in fused nested segmented reductions.
Prelude function not for negating booleans.

Fixed

Some incorrect removal of copies (#1505).
Handling of parametric modules with top-level existentials (#1510).
Module substitution fixes (#1512, #1518).
Invalid in-place lowering (#1523).
Incorrect code generation for some intra-group parallel code versions.
Flattening crash in the presence of irregular parallelism (#1525).
Incorrect substitution of type abbreviations with hidden sizes (#1531).
Proper handling of NaN in min/max functions for f16/f32/f64 in interpreter (#1528).

[0.20.6]

Added

Much better code generation for segmented scans with vectorisable operators.

Fixed

Fixes to extremely exotic GPU scans involving array operators.
Missing alias tracking led to invalid rewrites, causing a compiler crash (#1499).
Top-level bindings with existential sizes were mishandled (#1500, #1501).
A variety of memory leaks in the multicore backend, mostly (or perhaps exclusively) centered around context freeing or failing programs - this should not have affected many people.
Various fixes to f16 handling in the GPU backends.

[0.20.5]

Added

Existential sizes can now be explicitly quantified in type expressions (#1308).
Significantly expanded error index.
Attributes can now be numeric.
Patterns can now have attributes. None have any effect at the moment.
futhark autotune and futhark bench now take a --spec-file option for loading a test specification from another file.

Fixed

auto output reference datasets are now recreated when the program is newer than the data files.
Exotic hoisting bug (#1490).

[0.20.4]

Added

Tuning parameters now (officially) exposed in the C API.
futhark autotune is now 2-3x faster on many programs, as it now keeps the process running.
Negative numeric literals are now allowed in case patterns.

Fixed

futhark_context_config_set_profiling was missing for the c backend.
Correct handling of nested entry points (#1478).
Incorrect type information recorded when doing in-place lowering (#1481).

[0.20.3]

Added

Executables produced by C backends now take a --no-print-result option.
The C backends now generate a manifest when compiling with --library. This can be used by FFI generators (#1465).
The beginnings of a Rust-style error index.
scan on newer CUDA devices is now much faster.

Fixed

Unique opaque types are named properly in entry points.
The CUDA backend in library mode no longer exit()s the process if NVRTC initialisation fails.

[0.20.2]

Fixed

Simplification bug (#1455).
In-place-lowering bug (#1457).
Another in-place-lowering bug (#1460).
Don't try to tile inside loops with parameters with variant sizes (#1462).
Don't consider it an ICE when the user passes invalid command line options (#1464).

[0.20.1]

Added

The #[trace] and #[break] attributes now replace the trace and break functions (although they are still present in slightly-reduced but compatible form).
The #[opaque] attribute replaces the opaque function, which is now deprecated.
Tracing now works in compiled code, albeit with several caveats (mainly, it does not work for code running on the GPU).
New wasm and wasm-multicore backends by Philip Lassen. Still very experimental; do not expect API stability.
New intrinsic type f16, along with a prelude module f16. Implemented with hardware support where it is available, and with f32-based emulation where it is not.
Sometimes slightly more informative error message when input of the wrong type is passed to a test program.

Changed

The ! function in the integer modules is now called not.
! is now builtin syntax. You can no longer define a function called !. It is extremely unlikely this affects you. This removes the last special-casing of prefix operators.
A prefix operator section (i.e. (!)) is no longer permitted (and it never was according to the grammar).
The offset parameter for the "raw" array creation functions in the C API is now int64_t instead of int.

Fixed

i64.abs was wrong for arguments that did not fit in an i32.
Some f32 operations (**, abs, max) would be done in double precision on the CUDA backend.
Yet another defunctorisation bug (#1397).
The clz function would sometimes exhibit undefined behaviour in CPU code (#1415).
Operator priority of prefix - was wrong - it is now the same as ! (#1419).
futhark hash is now invariant to source location as well as stable across OS/compiler/library versions.
futhark literate is now much better at avoiding unnecessary recalculation.
Fixed a hole in size type checking that would usually lead to compiler crashes (#1435).
Underscores now allowed in numeric literals in test data (#1440).
The cuda backend did not use single-pass segmented scans as intended. Now it does.

[0.19.7]

Added

A new memory reuse optimisation has been added. This results in slightly lower footprint for many programs.
The cuda backend now uses a fast single-pass implementation for segmented scans, due to Morten Tychsen Clausen (#1375).
futhark bench now prints interim results while it is running.

Fixed

futhark test now provides better error message when asked to test an undefined entry point (#1367).
futhark pkg now detects some nonsensical package paths (#1364).
FutharkScript now parses f x y as applying f to x and y, rather than as f (x y).
Some internal array utility functions would not be generated if entry points exposed both unit arrays and boolean arrays (#1374).
Nested reductions used (much) more memory for intermediate results than strictly needed.
Size propagation bug in defunctionalisation (#1384).
In the C FFI, array types used only internally to implement opaque types are no longer exposed (#1387).
futhark bench now copes with test programs that consume their input (#1386). This required an extension of the server protocol as well.

[0.19.6]

Added

f32.hypot and f64.hypot are now much more numerically exact in the interpreter.
Generated code now contains a header with information about the version of Futhark used (and maybe more information in the future).
Testing/benchmarking with large input data (including randomly generated data) is much faster, as each file is now only read once.
Test programs may now use arbitrary FutharkScript expressions to produce test input, in particular expressions that produce opaque values. This affects both testing, benchmarking, and autotuning.
Compilation is about 10% faster, especially for large programs.

Fixed

futhark repl had trouble with declarations that produced unknown sizes (#1347).
Entry points can now have same name as (undocumented!) compiler intrinsics.
FutharkScript now detects too many arguments passed to functions.
Sequentialisation bug (#1350).
Missing causality check for index sections.
futhark test now reports mismatches using proper indexes (#1356).
Missing alias checking in fusion could lead to compiler crash (#1358).
The absolute value of NaN is no longer infinity in the interpreter (#1359).
Proper detection of zero strides in compiler (#1360).
Invalid memory accesses related to internal bookkeeping of bounds checking.

[0.19.5]

Added

Initial work on granting programmers more control over existential sizes, starting with making type abbreviations function as existential quantifiers (#1301).
FutharkScript now also supports arrays and scientific notation.
Added f32.epsilon and f64.epsilon for the difference between 1.0 and the next larger representable number.
Added f32.hypot and f64.hypot for your hypothenuse needs (#1344).

Local size bindings in let expressions, e.g:

let [n] (xs': [n]i32) = filter (>0) xs
in ...

Fixed

futhark_context_report() now internally calls futhark_context_sync() before collecting profiling information (if applicable).
futhark literate: Parse errors for expression directives now detected properly.
futhark autotune now works with the cuda backend (#1312).
Devious fusion bug (#1322) causing compiler crashes.
Memory expansion bug for certain complex GPU kernels (#1328).
Complex expressions in index sections (#1332).
Handling of sizes in abstract types in the interpreter (#1333).
Type checking of explicit size requirements in loop parameter (#1324).
Various alias checking bugs (#1300, #1340).

[0.19.4]

Fixed

Some uniqueness ignorance in fusion (#1291).
An invalid transformation could in rare cases cause race conditions (#1292).
Generated Python and C code should now be warning-free.
Missing check for uses of size-lifted types (#1294).
Error in simplification of concatenations could cause compiler crashes (#1296).

[0.19.3]

Added

Better futhark test/futhark bench errors when test data does not have the expected type.

Fixed

Mismatch between how thresholds were printed and what the autotuner was looking for (#1269).
zip now produces unique arrays (#1271).
futhark literate no longer chokes on lines beginning with -- without a following whitespace.
futhark literate: :loadimg was broken due to overzealous type checking (#1276).
futhark literate: :loadimg now handles relative paths properly.
futhark hash no longer considers the built-in prelude.
Server executables had broken store/restore commands for opaque types.

[0.19.2]

Added

New subcommand: futhark hash.
futhark literate is now smart about when to regenerate image and animation files.
futhark literate now produces better error messages passing expressions of the wrong type to directives.

Fixed

Type-checking of higher-order functions that take consuming funtional arguments.
Missing cases in causality checking (#1263).
f32.sgn was mistakenly defined with double precision arithmetic.
Only include double-precision atomics if actually needed by program (this avoids problems on devices that only support single precision).
A lambda lifting bug due to not handling existential sizes produced by loops correctly (#1267).
Incorrect uniqueness attributes inserted by lambda lifting (#1268).
FutharkScript record expressions were a bit too sensitive to whitespace.

[0.19.1]

Added

futhark literate now supports a $loadimg builtin function for passing images to Futhark programs.
The futhark literate directive for generating videos is now :video.
Support for 64-bit atomics on CUDA and OpenCL for higher performance with reduce_by_index in particular. Double-precision float atomics are used on CUDA.
New functions: f32.recip and f64.recip for multiplicative inverses.
Executables produced with the c and multicore backends now also accept --tuning and --size options (although there are not yet any tunable sizes).
New functions: scatter_2d and scatter_3d for scattering to multi-dimensional arrays (#1258).

Removed

The math modules no longer define the name negate (use neg instead).

Fixed

Exotic core language alias tracking bug (#1239).
Issue with entry points returning constant arrays (#1240).
Overzealous CSE collided with uniqueness types (#1241).
Defunctionalisation issue (#1242).
Tiling inside multiply nested loops (#1243).
Substitution bug in interpreter (#1250).
f32.sgn/f64.sgn now correct for NaN arguments.
CPU backends (c/multicore) are now more careful about staying in single precision for f32 functions (#1253).
futhark test and futhark bench now detect program initialisation errors in a saner way (#1246).
Partial application of operators with parameters used in a size-dependent way now works (#1256).
An issue regarding abstract size-lifted sum types (#1260).

[0.18.6]

Added

The C API now exposes serialisation functions for opaque values.
The C API now lets you pick which stream (if any) is used for logging prints (#1214).
New compilation mode: --server. For now used to support faster benchmarking and testing tools, but can be used to build even fancier things in the future (#1179).
Significantly faster reading/writing of large values. This mainly means that validation of test and benchmark results is much faster (close to an order of magnitude).
The experimental futhark literate command allows vaguely a notebook-like programming experience.
All compilers now accept an --entry option for treating more functions as entry points.
The negate function is now neg, but negate is kept around for a short while for backwards compatibility.
Generated header-files are now declared extern "C" when processed with a C++ compiler.
Parser errors in test blocks used by futhark bench and futhark test are now reported with much better error messages.

Fixed

Interaction between slice simplification and in-place updates (#1222).
Problem with user-defined functions with the same name as intrinsics.
Names from transitive imports no longer leak into scope (#1231).
Pattern-matching unit values now works (#1232).

[0.18.5]

Fixed

Fix tiling crash (#1203).
futhark run now does slightly more type-checking of its inputs (#1208).
Sum type deduplication issue (#1209).
Missing parentheses when printing sum values in interpreter.

[0.18.4]

Added

When compiling to binaries in the C-based backends, the compiler now respects the CFLAGS and CC environment variables.
GPU backends: avoid some bounds-checks for parallel sections inside intra-kernel loops.
The cuda backend now uses a much faster single-pass scan implementation, although only for nonsegmented scans where the operator operates on scalars.

Fixed

futhark dataset now correctly detects trailing commas in textual input (#1189).
Fixed local memory capacity check for intra-group-parallel GPU kernels.
Fixed compiler bug on segmented rotates where the rotation amount is variant to the nest (#1192).
futhark repl no longer crashes on type errors in given file (#1193).
Fixed a simplification error for certain arithmetic expressions (#1194).
Fixed a small uniqueness-related bug in the compilation of operator section.
Sizes of opaque entry point arguments are now properly checked (related to #1198).

[0.18.3]

Fixed

Python backend now disables spurious NumPy overflow warnings for both library and binary code (#1180).
Undid deadlocking over-synchronisation for freeing opaque objects.
futhark datacmp now handles bad input files better (#1181).

[0.18.2]

Added

The GPU loop tiler can now handle loops where only a subset of the input arrays are tiled. Matrix-vector multiplication is one important program where this helps (#1145).
The number of threads used by the multicore backend is now configurable (--num-threads and futhark_context_config_set_num_threads()). (#1162)

Fixed

PyOpenCL backend would mistakenly still streat entry point argument sizes as 32 bit.
Warnings are now reported even for programs with type errors.
Multicore backend now works properly for very large iteration spaces.
A few internal generated functions (init_constants(), free_constants()) were mistakenly declared non-static.
Process exit code is now nonzero when compiler bugs and limitations are encountered.
Multicore backend crashed on reduce_by_index with nonempty target and empty input.
Fixed a flattening issue for certain complex map nestings (#1168).
Made API function futhark_context_clear_caches() thread safe (#1169).
API functions for freeing opaque objects are now thread-safe (#1169).
Tools such as futhark dataset no longer crash with an internal error if writing to a broken pipe (but they will return a nonzero exit code).
Defunctionalisation had a name shadowing issue that would crop up for programs making very advanced use of functional representations (#1174).
Type checker erroneously permitted pattern-matching on string literals (this would fail later in the compiler).
New coverage checker for pattern matching, which is more correct. However, it may not provide quite as nice counter-examples (#1134).
Fix rare internalisation error (#1177).

[0.18.1]

Added

Experimental multi-threaded CPU backend, multicore.

Changed

All sizes are now of type i64. This has wide-ranging implications and most programs will need to be updated (#134).

[0.17.3]

Added

Improved parallelisation of futhark bench compilation.

Fixed

Dataset generation for test programs now use the right futhark executable (#1133).
Really fix NaN comparisons in interpreter (#1070, again).
Fix entry points with a parameter that is a sum type where multiple constructors contain arrays of the same statically known size.
Fix in monomorphisation of types with constant sizes.
Fix in in-place lowering (#1142).
Fix tiling inside multiple nested loops (#1143).

[0.17.2]

Added

Obscure loop optimisation (#1110).
Faster matrix transposition in C backend.
Library code generated with CUDA backend can now be called from multiple threads.
Better optimisation of concatenations of array literals and replicates.
Array creation C API functions now accept const pointers.
Arrays can now be indexed (but not sliced) with any signed integer type (#1122).
Added --list-devices command to OpenCL binaries (#1131)
Added --help command to C, CUDA and OpenCL binaries (#1131)

Removed

The integer modules no longer contain iota and replicate functions. The top-level ones still exist.
The size module type has been removed from the prelude.

Changed

Range literals may no longer be produced from unsigned integers.

Fixed

Entry points with names that are not valid C (or Python) identifiers are now pointed out as problematic, rather than generating invalid C code.
Exotic tiling bug (#1112).
Missing synchronisation for in-place updates at group level.
Fixed (in a hacky way) an issue where reduce_by_index would use too much local memory on AMD GPUs when using the OpenCL backend.

[0.16.4]

Added

#[unroll] attribute.
Better error message when writing a[i][j] (#1095).
Better error message when missing "in" (#1091).

Fixed

Fixed compiler crash on certain patterns of nested parallelism (#1068, #1069).
NaN comparisons are now done properly in interpreter (#1070).
Fix incorrect movement of array indexing into branches ifs (#1073).
Fix defunctorisation bug (#1088).
Fix issue where loop tiling might generate out-of-bounds reads (#1094).
Scans of empty arrays no longer result in out-of-bounds memory reads.
Fix yet another defunctionalisation bug due to missing eta-expansion (#1100).

[0.16.3]

Added

random input blocks for futhark test and futhark bench now support floating-point literals, which must always have either an f32 or f64 suffix.
The cuda backend now supports the -d option for executables.
The integer modules now contain a ctz function for counting trailing zeroes.

Fixed

The pyopencl backend now works with OpenCL devices that have multiple types (most importantly, oclgrind).
Fix barrier divergence when generating code for group-level colletive copies in GPU backend.
Intra-group flattening now looks properly inside of branches.
Intra-group flattened code versions are no longer used when the resulting workgroups would have less than 32 threads (with default thresholds anyway) (#1064).

[0.16.2]

Added

futhark autotune: added --pass-option.

Fixed

futhark bench: progress bar now correct when number of runs is less than 10 (#1050).
Aliases of arguments passed for consuming parameters are now properly checked (#1053).
When using a GPU backend, errors are now properly cleared. Previously, once e.g. an out-of-bounds error had occurred, all future operations would fail with the same error.
Size-coercing a transposed array no longer leads to invalid code generation (#1054).

[0.16.1]

Added

Incremental flattening is now performed by default. Use attributes to constrain and direct the flattening if you have exotic needs. This will likely need further iteration and refinement.
Better code generation for reverse (and the equivalent explicit slice).
futhark bench now prints progress bars.
The cuda backend now supports similar profiling as the opencl option, although it is likely slightly less accurate in the presence of concurrent operations.
A preprocessor macro FUTHARK_BACKEND_foo is now defined in generated header files, where foo is the name of the backend used.
Non-inlined functions (via #[noinline]) are now supported in GPU code, but only for functions that exclusively operate on scalars.
futhark repl now accepts a command line argument to load a program initially.
Attributes are now also permitted on declarations and specs.
futhark repl now has a :nanbreak command (#839).

Removed

The C# backend has been removed (#984).
The unsafe keyword has been removed. Use #[unsafe] instead.

Changed

Out-of-bounds literals are now an error rather than a warning.
Type ascriptions on entry points now always result in opaque types when the underlying concrete type is a tuple (#1048).

Fixed

Fix bug in slice simplification (#992).
Fixed a typer checker bug for tracking the aliases of closures (#995).
Fixed handling of dumb terminals in futhark test (#1000).
Fixed exotic monomorphisation case involving lifted type parameters instantiated with functions that take named parameters (#1026).
Further tightening of the causality restriction (#1042).
Fixed alias tracking for right-operand operator sections (#1043).

[0.15.8]

Added

Warnings for overflowing literals, such as 1000 : u8.
Futhark now supports an attribute system, whereby expressions can be tagged with attributes that provide hints or directions to the compiler. This is an expert-level feature, but it is sometimes useful.

[0.15.7]

Added

Faster index calculations for very tight GPU kernels (such as the ones corresponding to 2D tiling).
scan with vectorised operators (e.g. map2 (+)) is now faster in some cases.
The C API has now been documented and stabilized, including obtaining profiling information (although this is still unstructured).

Fixed

Fixed some cases of missing fusion (#953).
Context deinitialisation is now more complete, and should not leak memory (or at least not nearly as much, if any). This makes it viable to repeatedly create and free Futhark contexts in the same process (although this can still be quite slow).

[0.15.6]

Added

Binary operators now act as left-to-right sequence points with respect to size types.
futhark bench now has more colourful and hopefully readable output.
The compiler is now about 30% faster for most nontrivial programs. This is due to parallelising the inlining stage, and tweaking the default configuration of the Haskell RTS.
futhark dataset is now about 8-10x faster.

Fixed

Fixed some errors regarding constants (#941).
Fixed a few missing type checker cases for sum types (#938).
Fix OOB write in CUDA backend runtime code (#950).

[0.15.5]

Added

reduce_by_index with f32-addition is now approximately 2x faster in the CUDA backend.

Fixed

Fixed kernel extractor bug in if-interchange (#921).
Fixed some cases of malformed kernel code generation (#922).
Fixed rare memory corruption bug involving branches returning arrays (#923).
Fixed spurious warning about entry points involving opaque return types, where the type annotations are put on a higher-order return type.
Fixed incorrect size type checking for sum types in negative position with unknown constructors (#927).
Fixed loop interchange for permuted sequential loops with more than one outer parallel loop (#928).
Fixed a type checking bug for branches returning incomplete sum types (#931).

[0.15.4]

Added

futhark pkg now shells out to curl for HTTP requests.
futhark doc now supports proper GitHub-flavored Markdown, as it uses the cmark-gfm library internally.
Top-level constants are now executed only once per program instance. This matters when Futhark is used to generate library code.
futhark autotune is better at handling degrees of parallelism that assume multiple magnitudes during a single run.
futhark pkg now uses curl to retrieve packages.
Type errors are now printed in red for better legibility (thanks to @mxxo!).

Fixed

Fixed incorrect handling of opaques in entry point return types.
futhark pkg now works properly with GitLab (#899).

[0.15.3]

Added

scan now supports operators whose operands are arrays. They are significantly slower than primitive-typed scans, so avoid them if at all possible.
Precomputed constants are now handled much more efficiently.
Certain large programs that rely heavily on inlining now compile orders of magnitude faster.

Fixed

Some fixes to complicated module expressions.
futhark pkg should no longer crash uncontrollably on network errors (#894).
Fixed local open in interpreter (#887).
Fix error regarding entry points that called other entry points which contained local functions (#895).
Fix loading OpenCL kernels from a binary.

[0.15.2]

Fixed

Fix a REPL regression that made it unable to handle overloaded types (such as numeric literals, oops).
The uniqueness of a record is now the minimum of the uniqueness of any of its elements (#870).
Bug in causality checking has been fixed (#872).
Invariant memory allocations in scan/reduce operators are now supported.
futhark run now performs more type checking on entry point input (#876).
Compiled Futhark programs now check for EOF after the last input argument has been read (#877).
Fixed a bug in loop type checking that prevented the result from ever aliasing the initial parameter values (#879).

[0.15.1]

Added

Futhark now type-checks size annotations using a size-dependent type system.
The parallel code generators can now handle bounds checking and other safety checks.
Integer division by zero is now properly safety-checked and produces an error message.
Integer exponentiation with negative exponent is now properly safety-checked and produces an error message.
Serious effort has been put into improving type errors.
reduce_by_index may be somewhat faster for complex operators on histograms that barely fit in local memory.
Improved handling of in-place updates of multidimensional arrays nested in map. These are now properly parallelised.
Added concat_to and flatten_to functions to prelude.
Added indices function to the prelude.
futhark check and all compilers now take a -w option for disabling warnings.
futhark bench now accepts --pass-compiler-option.
The integer modules now have mad_hi and mul_hi functions for getting the upper part of multiplications. Thanks to @porcuquine for the contribution!
The f32 and f64 modules now also define sinh, cosh, tanh, asinh, acosh, and atanh functions.
The f32 and f64 modules now also define fma and mad functions.

Removed

Removed update, split2, intersperse, intercalate, pick, steps, and range from the prelude.

Changed

"futlib" is now called "prelude", and it is now an error to import it explicitly.

Fixed

Corrected address calculations in csharp backend.
The C backends are now more careful about generating overflowing integer operations (since this is undefined behaviour in C, but defined in Futhark).
futhark dataset no longer crashes uncontrollably when used incorrectly (#849).

[0.14.1]

Added

The optimiser is now somewhat better at removing unnecessary copies of array slices.
futhark bench and futhark test now take a --concurrency option for limiting how many threads are used for housekeeping tasks. Set this to a low value if you run out of memory.
random test blocks are now allowed to contain integer literals with type suffixes.
:frame <n> command for futhark repl for inspecting the stack.
e :> t notation, which means the same as e : t for now, but will have looser constraints in the future.
Size-lifted type abbreviations can be declared with type~ and size-lifted type parameters with '~. These currently have no significant difference from fully lifted types.

Changed

Tuples are now 0-indexed (#821, which also includes a conversion script).
Invalid ranges like 1..<0 now produce a run-time error instead of an empty array.
Record updates (r with f = e) now require r to have a completely known type up to f. This is a restriction that will hopefully be lifted in the future.
The backtrace format has changed to be innermost-first, like pretty much all other languages.
Value specs must now explicitly quantify all sizes of function parameters. Instead of
```
val sum: []t -> t
```
you must write
```
val sum [n]: [n]t -> t
```
futhark test now once again numbers un-named data sets from 0 rather than from 1. This fits a new general principle of always numbering from 0 in Futhark.
Type abbreviations declared with type may no longer contain functions or anonymous sizes in their definition. Use type^ for these cases. Just a warning for now, but will be an error in the future.

Fixed

Work around (probable) AMD OpenCL compiler bug for reduce_by_index operations with complex operators that require locking.
Properly handle another ICE on parse errors in test stanzas (#819).
futhark_context_new_with_command_queue() now actually works. Oops.
Different scopes are now properly addressed during type inference (#838). Realistically, there will still be some missing cases.

[0.13.2]

Added

New subcommand, futhark query, for looking up information about the name at some position in a file. Intended for editor integration.
(Finally) automatic support for compute model 7.5 in the CUDA backend.
Somewhat better performance for very large target arrays for reduce_by_index..

Fixed

Fixed a slice-iota simplification bug (#813).
Fixed defunctionalisation crash involving intrinsics (#814).

[0.13.1]

Added

Stack traces are now multiline for better legibility.

Changed

The empty(t) notation now specifies the type of the entire value (not just the element type), and requires dimension sizes when t is an array (e.g. empty(i32) is no longer allowed, you need for example empty([0]i32)).
All input files are now assumed to be in UTF-8.

Fixed

Fixed exponential-time behaviour for certain kernels with large arithmetic expressions (#805).
futhark test and friends no longer crash when reporting some errors (#808).
Fix uniqueness of loop results (#810).

[0.12.3]

Added

Character literals can now be any integer type.
The integer modules now have popc and clz functions.
Tweaked inlining so that larger programs may now compile faster (observed about 20%).
Pattern-matching on large sum typed-values taken from arrays may be a bit faster.

Fixed

Various small fixes to type errors.
All internal functions used in generated C code are now properly declared static.
Fixed bugs when handling dimensions and aliases in type ascriptions.

[0.12.2]

Added

New tool: futhark autotune, for tuning the threshold parameters used by incremental flattening. Based on work by Svend Lund Breddam, Simon Rotendahl, and Carl Mathias Graae Larsen.
New tool: futhark dataget, for extracting test input data. Most will probably never use this.
Programs compiled with the cuda backend now take options --default-group-size, --default-num-groups, and --default-tile-size.
Segmented reduce_by_index are now substantially fasted for small histograms.
New functions: f32.lerp and f64.lerp, for linear interpolation.

Fixed

Fixes to aliasing of record updates.
Fixed unnecessary array duplicates after coalescing optimisations.
reduce_by_index nested in maps will no longer sometimes require huge amounts of memory.
Source location now correct for unknown infix operators.
Function parameters are no longer in scope of themselves (#798).
Fixed a nasty out-of-bounds error in handling of irregular allocations.
The floor/ceil functions in f32/f64 now handle infinities correctly (and are also faster).
Using % on floats now computes fmod instead of crashing the compiler.

[0.12.1]

Added

The internal representation of parallel constructs has been overhauled and many optimisations rewritten. The overall performance impact should be neutral on aggregate, but there may be changes for some programs (please report if so).
Futhark now supports structurally typed sum types and pattern matching! This work was done by Robert Schenck. There remain some problems with arrays of sum types that themselves contain arrays.
Significant reduction in compile time for some large programs.
Manually specified type parameters need no longer be exhaustive.
Mapped rotate is now simplified better. This can be particularly helpful for stencils with wraparound.

Removed

The ~ prefix operator has been removed. ! has been extended to perform bitwise negation when applied to integers.

Changed

The --futhark option for futhark bench and futhark test now defaults to the binary being used for the subcommands themselves.
The legacy futhark -t option (which did the same as futhark check) has been removed.
Lambdas now bind less tightly than type ascription.
stream_map is now map_stream and stream_red is now reduce_stream.

Fixed

futhark test now understands --no-tuning as it was always supposed to.
futhark bench and futhark test now interpret --exclude in the same way.
The Python and C# backends can now properly read binary boolean input.

[0.11.2]

Fixed

Entry points whose types are opaque due to module ascription, yet whose representation is simple (scalars or arrays of scalars) were mistakely made non-opaque when compiled with --library. This has been fixed.
The CUDA backend now supports default sizes in .tuning files.
Loop interchange across multiple dimensions was broken in some cases (#767).
The sequential C# backend now generates code that compiles (#772).
The sequential Python backend now generates code that runs (#765).

[0.11.1]

Added

Segmented scans are a good bit faster.
reduce_by_index has received a new implementation that uses local memory, and is now often a good bit faster when the target array is not too large.
The f32 and f64 modules now contain gamma and lgamma functions. At present these do not work in the C# backend.
Some instances of reduce with vectorised operators (e.g. map2 (+)) are orders of magnitude faster than before.
Memory usage is now lower on some programs (specifically the ones that have large maps with internal intermediate arrays).

Removed

Size parameters (not annotations) are no longer permitted directly in let and loop bindings, nor in lambdas. You are likely not affected (except for the stream constructs; see below). Few people used this.

Changed

The array creation functions exported by generated C code now take int64_t arguments for the shape, rather than int. This is in line with what the shape functions return.
The types for stream_map, stream_map_per, stream_red, and stream_red_per have been changed, such that the chunk function now takes the chunk size as the first argument.

Fixed

Fixes to reading values under Python 3.
The type of a variable can now be deduced from its use as a size annotation.
The code generated by the C-based backends is now also compilable as C++.
Fix memory corruption bug that would occur on very large segmented reductions (large segments, and many of them).

[0.10.2]

Added

reduce_by_index is now a good bit faster on operators whose arguments are two 32-bit values.
The type checker warns on size annotations for function parameters and return types that will not be visible from the outside, because they refer to names nested inside tuples or records. For example, the function
```
let f (n: i32, m: i32): [n][m]i32 = ...
```
will cause such a warning. It should instead be written
```
let f (n: i32) (m: i32): [n][m]i32 = ...
```
A new library function futhark_context_config_select_device_interactively() has been added.

Fixed

Fix reading and writing of binary files for C-compiled executables on Windows.
Fixed a couple of overly strict internal sanity checks related to in-place updates (#735, #736).
Fixed a couple of convoluted defunctorisation bugs (#739).

[0.10.1]

Added

Using definitions from the intrinsic module outside the prelude now results in a warning.
reduce_by_index with vectorised operators (e.g. map2 (+)) is orders of magnitude faster than before.
Executables generated with the pyopencl backend now support the options --default-tile-size, --default-group-size, --default-num-groups, --default-threshold, and --size.
Executables generated with c and opencl now print a help text if run with invalid options. The py and pyopencl backends already did this.
Generated executables now support a --tuning flag for passing many tuned sizes in a file.
Executables generated with the cuda backend now take an --nvrtc-option option.
Executables generated with the opencl backend now take a --build-option option.

Removed

The old futhark-* executables have been removed.

Changed

If an array is passed for a function parameter of a polymorphic type, all arrays passed for parameters of that type must have the same shape. For example, given a function
```
let pair 't (x: t) (y: t) = (x, y)
```
The application pair [1] [2,3] will now fail at run-time.
futhark test now numbers un-named data sets from 1 rather than 0. This only affects the text output and the generated JSON files, and fits the tuple element ordering in Futhark.
String literals are now of type []u8 and contain UTF-8 encoded bytes.

Fixed

An significant problematic interaction between empty arrays and inner size declarations has been closed (#714). This follows a range of lesser empty-array fixes from 0.9.1.
futhark datacmp now prints to stdout, not stderr.
Fixed a major potential out-of-bounds access when sequentialising reduce_by_index (in most cases the bug was hidden by subsequent C compiler optimisations).
The result of an anonymous function is now also forbidden from aliasing a global variable, just as with named functions.
Parallel scans now work correctly when using a CPU OpenCL implementation.
reduce_by_index was broken on newer NVIDIA GPUs when using fancy operators. This has been fixed.

[0.9.1]

Added

futhark cuda: a new CUDA backend by Jakob Stokholm Bertelsen.
New command for comparing data files: futhark datacmp.
An :mtype command for futhark repl that shows the type of a module expression.
futhark run takes a -w option for disabling warnings.

Changed

Major command reorganisation: all Futhark programs have been combined into a single all-powerful futhark program. Instead of e.g. futhark-foo, use futhark foo. Wrappers will be kept around under the old names for a little while. futharki has been split into two commands: futhark repl and futhark run. Also, py has become python and cs has become csharp, but pyopencl and csopencl have remained as they were.
The result of a function is now forbidden from aliasing a global variable. Surprisingly little code is affected by this.
A global definition may not be ascribed a unique type. This never had any effect in the first place, but now the compiler will explicitly complain.
Source spans are now printed in a slightly different format, with ending the line number omitted when it is the same as the start line number.

Fixed

futharki now reports source locations of trace expressions properly.
The type checker now properly complains if you try to define a type abbreviation that has unused size parameters.

[0.8.1]

Added

Now warns when /futlib/... files are redundantly imported.
futharki now prints warnings for files that are ":load"ed.
The compiler now warns when entry points are declared with types that will become unnamed and opaque, and thus impossible to provide from the outside.
Type variables invented by the type checker will now have a unicode subscript to distinguish them from type parameters originating in the source code.
futhark-test and futhark-bench now support generating random test data.
The library backends now generate proper names for arrays of opaque values.
The parser now permits empty programs.
Most transpositions are now a good bit faster, especially on NVIDIA GPUs.

Removed

The <- symbol can no longer be used for in-place updates and record updates (deprecated in 0.7.3).

Changed

Entry points that accept a single tuple-typed parameter are no longer silently rewritten to accept multiple parameters.

Fixed

The :type command in futharki can now handle polymorphic expressions (#669).
Fixed serious bug related to chaining record updates.
Fixed type inference of record fields (#677).
futharki no longer goes in an infinite loop if a for loop contains a negative upper bound.
Overloaded number types can no longer carry aliases (#682).

[0.7.4]

Added

Support type parameters for operator specs defined with val.

Fixed

Fixed nasty defunctionalisation bug (#661).
cabal sdist and stack sdist works now.

[0.7.3]

Added

Significant performance changes: there is now a constant extra compilation overhead (less than 200ms on most machines). However, the rest of the compiler is 30-40% faster (or more in some cases).
A warning when ambiguously typed expressions are assigned a default (i32 or f64).
In-place updates and record updates are now written with = instead of <-. The latter is deprecated and will be removed in the next major version (#650).

Fixed

Polymorphic value bindings now work properly with module type ascription.
The type checker no longer requires types used inside local functions to be unambiguous at the point where the local function is defined. They must still be unambiguous by the time the top-level function ends. This is similar to what other ML languages do.
futhark-bench now writes "μs" instead of "us".
Type inference for infix operators now works properly.

[0.7.2]

Added

futhark-pkg now supports GitLab.
futhark-tests --notty option now has a --no-terminal alias. --notty is deprecated, but still works.
futhark-test now supports multiple entry points per test block.
Functional record updates: r with f <- x.

Fixed

Fix the -C option for futhark-test.
Fixed incorrect type of reduce_by_index.
Segmented reduce_by_index now uses much less memory.

[0.7.1]

Added

C# backend by Mikkel Storgaard Knudsen (futhark-cs/futhark-csopencl).
futhark-test and futhark-bench now take a --runner option.
futharki now uses a new interpreter that directly interprets the source language, rather than operating on the desugared core language. In practice, this means that the interactive mode is better, but that interpretation is also much slower.
A trace function that is semantically id, but makes futharki print out the value.
A break function that is semantically id, but makes futharki stop and provide the opportunity to inspect variables in scope.
A new SOAC, reduce_by_index, for expressing generalised reductions (sometimes called histograms). Designed and implemented by Sune Hellfritzsch.

Removed

Most of futlib has been removed. Use external packages instead:
- futlib/colour => https://github.com/athas/matte
- futlib/complex => https://github.com/diku-dk/complex
- futlib/date => https://github.com/diku-dk/date
- futlib/fft => https://github.com/diku-dk/fft
- futlib/linalg => https://github.com/diku-dk/fft
- futlib/merge_sort, futlib/radix_sort => https://github.com/diku-dk/sorts
- futlib/random => https://github.com/diku-dk/cpprandom
- futlib/segmented => https://github.com/diku-dk/segmented
- futlib/sobol => https://github.com/diku-dk/sobol
- futlib/vector => https://github.com/athas/vector
No replacement: futlib/mss, futlib/lss.
zip6/zip7/zip8 and their unzip variants have been removed. If you build gigantic tuples, you're on your own.
The >>> operator has been removed. Use an unsigned integer type if you want zero-extended right shifts.

Changed

The largest/smallest values for numeric modules have been renamed highest/lowest.

Fixed

Many small things.

[0.6.3]

Added

Added a package manager: futhark-pkg. See also the documentation.
Added log2 and log10 functions to f32 and f64.
Module type refinement (with) now permits refining parametric types.
Better error message when invalid values are passed to generated Python entry points.
futhark-doc now ignores files whose doc comment is the word "ignore".
copy now works on values of any type, not just arrays.
Better type inference for array indexing.

Fixed

Floating-point numbers are now correctly rounded to nearest even integer, even in exotic cases (#377).
Fixed a nasty bug in the type checking of calls to consuming functions (#596).

[0.6.2]

Added

Bounds checking errors now show the erroneous index and the size of the indexed array. Some other size-related errors also show more information, but it will be a while before they are all converted (and say something useful - it's not entirely straightforward).
Opaque types now have significantly more readable names, especially if you add manual size annotations to the entry point definitions.
Backticked infix operators can now be used in operator sections.

Fixed

f64.e is no longer pi.
Generated C library code will no longer abort() on application errors (#584).
Fix file imports on Windows.
futhark-c and futhark-opencl now generates thread-safe code (#586).
Significantly better behaviour in OOM situations.
Fixed an unsound interaction between in-place updates and parametric polymorphism (#589).

[0.6.1]

Added

The real module type now specifies tan.
futharki now supports entering declarations.
futharki now supports a :type command (or :t for short).
futhark-test and futhark-benchmark now support gzipped data files. They must have a .gz extension.
Generated code now frees memory much earlier, which can help reduce the footprint.
Compilers now accept a --safe flag to make them ignore unsafe.
Module types may now define lifted abstract types, using the notation type ^t. These may be instantiated with functional types. A lifted abstract type has all the same restrictions as a lifted type parameter.

Removed

The rearrange construct has been removed. Use transpose instead.
futhark-mode.el has been moved to a separate repository.
Removed |>> and <<|. Use >-> and <-< instead.
The empty construct is no longer supported. Just use empty array literals.

Changed

Imports of the basis library must now use an absolute path (e.g. /futlib/fft, not simply futlib/fft).
/futlib/vec2 and /futlib/vec3 have been replaced by a new /futlib/vector file.
Entry points generated by the C code backend are now prefixed with futhark_entry_ rather than just futhark_.
zip and unzip are no longer language constructs, but library functions, and work only on two arrays and pairs, respectively. Use functions zipN/unzipN (for 2<=n<=8).

Fixed

Better error message on EOF.
Fixed handling of .. in import paths.
Type errors (and other compiler feedback) will no longer contain internal names.
futhark-test and friends can now cope with infinities and NaNs. Such values are printed and read as f32.nan, f32.inf, -f32.inf, and similarly for f32. In futhark-test, NaNs compare equal.

[0.5.2]

Added

Array index section: (.[i]) is shorthand for (\x -> x[i]). Full slice syntax supported. (#559)
New assert construct. (#464)
futhark-mode.el now contains a definition for flycheck.

Fixed

The index produced by futhark-doc now contains correct links.
Windows linebreaks are now fully supported for test files (#558).

[0.5.1]

Added

Entry points need no longer be syntactically first-order.
Added overloaded numeric literals (#532). This means type suffixes are rarely required.
Binary and unary operators may now be bound in patterns by enclosing them in parenthesis.
futhark-doc now produces much nicer documentation. Markdown is now supported in documentation comments.
/futlib/functional now has operators >-> and <-< for function composition. <<| are |>> are deprecated.
/futlib/segmented now has a segmented_reduce.
Scans and reductions can now be horizontally fused.
futhark-bench now supports multiple entry points, just like futhark-test.
".." is now supported in include paths.

Removed

The reshape construct has been removed. Use the flatten/unflatten functions instead.
concat and rotate no longer support the @ notation. Use map nests instead.
Removed -I/--library. These never worked with futhark-test/futhark-bench anyway.

Changed

When defining a module type, a module of the same name is no longer defined (#538).
The default keyword is no longer supported.
/futlib/merge_sort and /futlib/radix_sort now define functions instead of modules.

Fixed

Better type inference for rearrange and rotate.
import path resolution is now much more robust.

[0.4.1]

Added

Unused-result elimination for reductions; particularly useful when computing with dual numbers for automatic differentiation.
Record field projection is now possible for variables of (then) unknown types. A function parameter must still have an unambiguous (complete) type by the time it finishes checking.

Fixed

Fixed interaction between type ascription and type inference (#529).
Fixed duplication when an entry point was also called as a function.
Futhark now compiles cleanly with GHC 8.4.1 (this is also the new default).

[0.4.0]

Added

The constructor for generated PyOpenCL classes now accepts a command_queue parameter (#480).
Transposing small arrays is now much faster when using OpenCL backend (#478).
Infix operators can now be defined in prefix notation, e.g.:
```
let (+) (x: i32) (y: i32) = x - y
```
This permits them to have type- and shape parameters.
Comparison operators (<=, <, >, >=) are now valid for boolean operands.
Ordinary functions can be used as infix by enclosing them in backticks, as in Haskell. They are left-associative and have lowest priority.
Numeric modules now have largest/smallest values.
Numeric modules now have sum, product, maximum, and minimum functions.
Added --Werror command line option to compilers.
Higher-order functions are now supported (#323).
Type inference is now supported, although with some limitations around records, in-place updates, and unzip. (#503)

Added a range of higher-order utility functions to the prelude, including (among others):

val (|>) '^a '^b: a ->  (a -> b) -> b

val (<|) '^a '^b: (a -> b) -> a -> b

val (|>>) '^a 'b '^c: (a -> b) -> (b -> c) -> a -> c

val (<<|) '^a 'b '^c: (b -> c) -> (a -> b) a -> c

Changed

FUTHARK_VERSIONED_CODE is now FUTHARK_INCREMENTAL_FLATTENING.
The SOACs map, reduce, filter, partition, scan, stream_red, and stream_map have been replaced with library functions.
The futlib/mss and futlib/lss modules have been rewritten to use higher-order functions instead of modules.

Fixed

Transpositions in generated OpenCL code no longer crashes on large but empty arrays (#483).
Booleans can now be compared with relational operators without crashing the compiler (#499).

[0.3.1]

Added

futhark-bench now tries to align benchmark results for better legibility.

Fixed

futhark-test: now handles CRLF linebreaks correctly (#471).
A record field can be projected from an array index expression (#473).
Futhark will now never automatically pick Apple's CPU device for OpenCL, as it is rather broken. You can still select it manually (#475).
Fixes to set_bit functions in the math module (#476).

[0.3.0]

Added

A comprehensible error message is now issued when attempting to run a Futhark program on an OpenCL that does not support the types used by the program. A common case was trying to use double-precision floats on an Intel GPU.
Parallelism inside of a branch can now be exploited if the branch condition and the size of its results is invariant to all enclosing parallel loops.
A new OpenCL memory manager can in some cases dramatically improve performance for repeated invocations of the same entry point.
Experimental support for incremental flattening. Set the environment variable FUTHARK_VERSIONED_CODE to any value to try it out.
futhark-dataset: Add -t/-type option. Useful for inspecting data files.
Better error message when ranges written with two dots (x..y).
Type errors involving abstract types from modules now use qualified names (less "expected 't', got 't'", more "expected 'foo.t', got 'bar.t'").
Shorter compile times for most programs.
futhark-bench: Add --skip-compilation flag.
scatter expressions nested in maps are now parallelised.
futlib: an fft module has been added, thanks to David P.H. Jørgensen and Kasper Abildtrup Hansen.

Removed

futhark-dataset: Removed --binary-no-header and --binary-only-header options.
The split language construct has been removed. There is a library function split that does approximately the same.

Changed

futlib: the complex module now produces a non-abstract complex type.
futlib: the random module has been overhauled, with several new engines and adaptors changed, and some of the module types changed. In particular, rng_distribution now contains a numeric module instead of an abstract type.
futlib: The vec2 and vec3 modules now represent vectors as records rather than tuples.
futlib: The linalg module now has distinct convenience functions for multiplying matrices with row and column vectors.
Only entry points defined directly in the file given to the compiler will be visible.
Range literals are now written without brackets: x...y.
The syntax (-x) can no longer be used for a partial application of subtraction.
futhark-test and futhark-bench will no longer append .bin to executables.
futhark-test and futhark-bench now replaces actual/expected files from previous runs, rather than increasing the litter.

Fixed

Fusion would sometimes remove safety checks on e.g. reshape (#436).
Variables used as implicit fields in a record construction are now properly recognised as being used.
futlib: the num_bits field for the integer modules in math now have correct values.

[0.2.0]

Added

Run-time errors due to failed assertions now include a stack trace.
Generated OpenCL code now picks more sensible group size and count when running on a CPU.
scatter expressions nested in maps may now be parallelised ("segmented scatter").
Add num_bits/get_bit/set_bit functions to numeric module types, including a new float module type.
Size annotations may now refer to preceding parameters, e.g:
```
let f (n: i32) (xs: [n]i32) = ...
```
futhark-doc: retain parameter names in generated docs.
futhark-doc: now takes -v/--verbose options.
futhark-doc: now generates valid HTML.
futhark-doc: now permits files to contain a leading documentation comment.
futhark-py/futhark-pyopencl: Better dynamic type checking in entry points.
Primitive functions (sqrt etc) can now be constant-folded.
Futlib: /futlib/vec2 added.

Removed

The built-in shape function has been removed. Use length or size parameters.

Changed

The from_i32/from_i64 functions of the numeric module type have been replaced with functions named i32/i64. Similarly functions have been added for all the other primitive types (factored into a new from_prim module type).
The overloaded type conversion functions (i32, f32, bool, etc) have been removed. Four functions have been introduced for the special cases of converting between f32/f64 and i32: r32, r64, t32, t64.
Modules and variables now inhabit the same name space. As a consequence, we now use x.y to access field y of record x.
Record expression syntax has been simplified. Record concatenation and update is no longer directly supported. However, fields can now be implicitly defined: {x,y} now creates a record with field x and y, with values taken from the variables x and y in scope.

Fixed

The != operator now works properly on arrays (#426).
Allocations were sometimes hoisted incorrectly (#419).
f32.e is no longer pi.
Various other fixes.

[0.1.0]

(This is just a list of highlights of what was included in the first release.)

Code generators: Python and C, both with OpenCL.
Higher-order ML-style module system.
In-place updates.
Tooling: futhark-test, futhark-bench, futhark-dataset, futhark-doc.
Beginnings of a basis library, "futlib".