From Phobos to Python

ph2py prints a Phobos source in its Python spelling. The Python it prints compiles, through the front end, to the same module as the .ph file. A release ships it beside phobos-compile; in a checkout it is the second binary of the phobos-compile crate. It needs no GPU.

ReleaseCheckout

Copy

ph2py examples/gemm_fp32.ph

cargo run -p phobos-compile --bin ph2py -- examples/gemm_fp32.ph

For the f32 GEMM it prints:

from __future__ import annotations

import phobos.lang as ph


@ph.kernel
@ph.autotune(TILE_M=[32, 256], TILE_N=[32, 256], TILE_K=[4, 32], U=[1, 8], T=[256, 128], IB=[32, 64])
@ph.launch("T")
@ph.index_bits("IB")
@ph.pipeline
@ph.aligned(M="TILE_M", N="TILE_N", K="TILE_K")
def gemm(A: ph.tensor[ph.f32][M, K], B: ph.tensor[ph.f32][K, N], C: ph.tensor[ph.f32][M, N], alpha: ph.f32, beta: ph.f32):
    pm: ph.let = ph.ctx.block.x
    pn: ph.let = ph.ctx.block.y
    acc: ph.var[ph.tile[ph.f32][TILE_M, TILE_N]] = 0.0
    for kt in ph.unroll(U, range(0, K, TILE_K)):
        a: ph.var = A[pm * TILE_M:+TILE_M, kt:+TILE_K]
        b: ph.var = B[kt:+TILE_K, pn * TILE_N:+TILE_N]
        acc += ph.dot(a, b)
    if beta == 0.0:
        C[pm * TILE_M:+TILE_M, pn * TILE_N:+TILE_N] = alpha * acc
    else:
        c_old: ph.let = C[pm * TILE_M:+TILE_M, pn * TILE_N:+TILE_N]
        C[pm * TILE_M:+TILE_M, pn * TILE_N:+TILE_N] = alpha * acc + beta * c_old

A directory at a time

ph2py --out DIR PATH... writes DIR/<stem>.py for each source: a file, or every .ph in a directory. It prints one line for each source it cannot spell, then a count.

ReleaseCheckout

Copy

ph2py --out py examples

cargo run -p phobos-compile --bin ph2py -- --out py examples

What it changes

The program is the same; a few constructs are respelled so Python reads them as Phobos does:

• A / that divides integers becomes //. Which / divides integers is decided by compiling the source at the default target; a / no kernel builds stays /.
• A variable or parameter named for a Python keyword, such as from, takes a trailing underscore, from_. No compiled module sees the difference.
• The comment a source opens with is kept, as a Python comment; the others are dropped.

Two things have no Python spelling and are errors: a kernel named for a Python keyword, and a fn whose / divides integers at one call and floats at another.

How it is checked

python/tests/roundtrip.py prints every .ph in the repository, the snapshot corpus and the generated kernels through ph2py, reads each back through the front end, and compares the emitted modules under the five targets the compiler is tested at. They are identical for every source that parses.