Penrose

We're building a prototype for set theory. Not ready for contributions or public use yet, but hopefully will be after this summer! See penrose.ink for more information.

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Usage

Install any relevant packages: cabal install $PACKAGE_NAME (though I'm told the Haskell community has moved on to the better stack package manager).

To compile both: ghc Runtime.hs

To just compile Compiler: ghc Compiler.hs

To use: ./Runtime <filename>.sub <filename>.sty

User interface:

• You can click and drag the objects, including labels. The optimization will pause while dragging and re-layout when the mouse is lifted. The object on top is semi-arbitrary, decided by the order of the objects in the internal list.
• Pressing the R key will resample the configuration.
• Pressing the A key will turn autostep (automatically stepping the optimization) on or off.
• Pressing the S key will step the optimization by one step if autostep is off. It won't do anything if autostep is on.

Examples of existing pairs:

• twosets.sub settheory.sty
• continuousmap1.sub continuousmap1.sty (system doesn't currently handle this)

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Organization

src contains the compiler and runtime.

src/GC-slides contains slides from weekly group meetings.

src/gifs and src/pictures contain GIFs and pictures documenting new features in the system.

Other directories in the root contain documentation and old parts of the system.

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More information

I use the following library to handle the graphics, animation, and user input: gloss.

Functionality of the current code:

• gradient-descent-based layout
• with backtracking line search
• for set theory with points, sets, and certain constraints on points and sets
• with very simple objective functions provided (e.g. centering)
• where the layout is animated and interactive (v. useful for debugging)

Some limitations:

• line search sometimes doesn't terminate
• need a better debugging interface for optimization, e.g. live parameter tuning

Parameters:

• stepsPerSecond: number of simulation steps for gloss to take for each second of real time
• picWidth, picHeight: canvas dimensions
• stepFlag: turns stepping the simulation on and off for debugging (no stepping = objects don't move)
• clampFlag: turns clamping gradient values on and off for debugging
• debug: turns on/off the debug print functions
• constraintFlag: turns constraint satisfaction on/off (currently off because we're doing unconstrained optimization)
• Default ambient objective functions are specified in ambientObjFns, and analogously for ambientConstrFns.
• Default objective functions are specified in genObjsAndFns.
• btls: turn on/off the backtracking line search for debugging (off = use a fixed timestep specified in the code)
• alpha and beta: parameters for the backtracking line search (see code for a more detailed description)
• stopEps: stopping condition sensitivity for gradient descent. Stop when magnitude of gradient is less than stopEps.

Debugging:

• Use the flags above.
• I also use ghci, the Haskell REPL. To load the file, do :l filename.hs. To import a library, paste in the normal import statement. To declare something, start with a let statement, e.g. let x = 5.
• For printing internal values, I use the Debug.Trace library.

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Design

• Compiler parses the Substance and Style programs and combines their abstract syntax trees into Layout (the intermediate layout representation).
• Runtime calls Compiler on the input files, and transforms the data in Layout to Opt (the representations used by the optimization code).
• Runtime imports Compiler as a module.

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Usage for old code

Compile: ghc settheory.hs

Create SVG: ./settheory -w 500 -h 500 -o set.svg (The parameters are the width and height of the rendered picture.)

Open SVG: chrome set.svg