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.

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 (see below). They are not necessarily an evaluation of the speed of the language.

Interpreters/JITs

Language	Time
Rust (Cranelift)	🏁 3.672
JavaScript-jit (Bun)	3.893
Lua-jit (LuaJIT)	4.142
Rust	6.624
Zig	8.010
JavaScript (Node.js)	24.274
C	41.715
Python-JIT	1:31.953
Lua (LuaJIT)	1:54.845
C#	4:23.246
F#	6:23.604
Nushell	days

AOT (Ahead-of-time) compilers

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

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

Useful Resources

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