BrainFetch

This is a collection of BrainF*** interpreters and compilers I wrote in various languages, both as a test of my abilities and as a test of the general performance of the languages in everyday computation tasks.

The implementations can be found in the src/ directory.

Current implementations include:

• C (most features)
• C-compiled (fastest)
• Python
• Rust (safest)
• Zig

Implementation Methods

There are a few different ways to create a BrainF*** interpreter, and my implementations typically start as one but incrementally convert to another:

• Direct interpretation
  • Pattern match directly on the input string
  • Slowest but simplest approach
  • May filter out comments ahead of time
• Tokenization
  • Filter and convert the input code into a string of tokens to execute on a VM
  • Dramatic speedups with BF code that has comments
  • May also group repeated commands together (e.g. ++++ -> (ADD, 4)) which can result in ~2x performance boost in many cases
  • May also optimize frequently-used command strings by converting them into single tokens (e.g. [-] -> ZERO)
• JIT (Just-in-time) compilation
  • Convert the BF code into some existing language or bytecode and rely on an existing runtime to execute it
  • Easier to do with scripted languages that have an exec function
• AOT (Ahead-of-time) compilation
  • Convert the BF code into equivalent source code for a compiled language like C or Rust, compile the code into a native binary, and execute it directly

Performance

Tests are run on a ThinkPad T480 with an Intel Core i5-8250U @ 3.40 GHz, running Arch Linux, and executing bf/mandelbrot.bf.

Also note that these implementations perform various levels of optimization, some being more complete than others. They are not necessarily an evaluation of the speed of the language.

Interpreters/JITs

Language	Time
C	41.715
C#	4:23.246
F#	6:23.604
JavaScript (nodejs)	43.983
Nushell	days
Python-JIT	1:31.953
Rust	6.624
Rust (Cranelift)	3.672
Zig	8.010

AOT (Ahead-of-time) compilers

Language	Compile Time	Run Time	Binary Size
Python -> C -> native	2.867	1.054	40184

Useful Resources

• Wikipedia article on BrainF***
• This random GitHub repo with a whole bunch of great BF example programs