Higher-order Virtual Machine 2 (HVM2) is a massively parallel Interaction Combinator evaluator.

By compiling programs from high-level languages (such as Python and Haskell) to HVM, one can run these languages directly on massively parallel hardware, like GPUs, with near-ideal speedup.

HVM2 is the successor to HVM1, a 2022 prototype of this concept. Compared to its predecessor, HVM2 is simpler, faster and, most importantly, stable and correct. HOC provides long-term support to all features listed on its REPORT.md.

This repository exposes a low-level IR language for specifyig the HVM2 nets, and a compiler from that language to C and CUDA. It is not meant for direct human usage. If you're looking for a high-level language to interface with HVM2, check Bend instead!

Install HVM2:

cargo +nightly install hvm

There are multiple ways to run an HVM program:

hvm run    <file.hvm> # interpret via Rust
hvm run-c  <file.hvm> # interpret via C
hvm run-cu <file.hvm> # interpret via CUDA
hvm gen-c  <file.hvm> # compile to standalone C
hvm gen-cu <file.hvm> # compile to standalone CUDA

All modes produce the same output. The compiled modes require you to compile the generated file (with gcc file.c -o file, for example), but are faster to run. The CUDA versions have much higher peak performance, but are less stable. As a rule of thumb, gen-c should be used in production.

HVMC is a low-level compile target for high-level languages. It provides a raw syntax for wiring interaction nets. For example:

@main = a
  & @sum ~ (28 (0 a))

@sum = (?(((a a) @sum__C0) b) b)

@sum__C0 = ({c a} ({$([*2] $([+1] d)) $([*2] $([+0] b))} f))
  &! @sum ~ (a (b $(:[+] $(e f))))
  &! @sum ~ (c (d e))

The file above implements a recursive sum. If that looks unreadable to you - don't worry, it isn't meant to. Bend is the human-readable presentation, and can be used both by end users, and languages aiming to target the HVM. Check it out!