Files
tilelang/testing/python/language/test_tilelang_cast_rounding.py
T
ec3be54879 [Feature] Add stochastic rounding cast for f32 -> fp8/fp4 on CUDA (#2260)
* Add draft

* Update tvm

* Fix lint

* Update 3rdparty/tvm

* Update CUDA compute version requirement in tilelang tests to 10.0

* Polish stochastic-cast comments

* Add rbits invariance tests for stochastic-cast

* Fix lint

---------

Co-authored-by: LeiWang1999 <leiwang1999@outlook.com>
Co-authored-by: wangxiangwen <xiangwen.wang@deepseek.com>
2026-05-28 20:02:38 +08:00

359 lines
13 KiB
Python

"""Tests for T.cast with round, sat, and rbits parameters."""
import pytest
import tilelang
import tilelang.testing
import tilelang.language as T
from tilelang.language.tir.ir import _VALID_CAST_ROUNDING_MODES
# T.cast is provided by tilelang.language.tir.ir (and re-exported by
# `from .tir.ir import *` in tilelang.language.__init__, overriding the
# upstream T.cast brought in by `from tvm.script.parser.tir import *`).
cast = T.cast
# ===========================================================================
# Validation tests (do not require GPU)
# ===========================================================================
def test_cast_invalid_round():
"""Test that invalid rounding modes raise ValueError."""
with pytest.raises(ValueError, match="Invalid round"):
cast(1.0, "float8_e4m3fn", round="invalid")
def test_cast_invalid_sat():
"""Test that non-bool sat raises ValueError."""
with pytest.raises(ValueError, match="Invalid sat"):
cast(1.0, "float8_e4m3fn", sat="invalid")
def test_cast_rs_requires_rbits():
"""Test that round='rs' requires rbits."""
with pytest.raises(ValueError, match="rbits is required"):
cast(1.0, "float8_e4m3fn", round="rs")
def test_cast_rbits_only_with_rs():
"""Test that rbits is only valid with round='rs'."""
with pytest.raises(ValueError, match="rbits is only valid"):
cast(1.0, "float8_e4m3fn", round="rn", rbits=T.int32(42))
def test_cast_valid_rounding_modes():
"""Test that all valid rounding modes are accepted (without rbits for non-rs)."""
for mode in _VALID_CAST_ROUNDING_MODES:
if mode in ("rs", ""):
continue
# Should not raise
cast(T.float32(1.0), "float8_e4m3fn", round=mode)
def test_cast_sat_bool():
"""Test that sat accepts True and False."""
# Should not raise
cast(T.float32(1.0), "float8_e4m3fn", sat=True)
cast(T.float32(1.0), "float8_e4m3fn", sat=False)
# ===========================================================================
# Codegen tests (require GPU with compute capability >= 8.9)
# ===========================================================================
@tilelang.testing.requires_cuda
@tilelang.testing.requires_cuda_compute_version_ge(8, 9)
def test_cast_default_unchanged():
"""Test that T.cast without rounding params still uses __nv_cvt_float2_to_fp8x2."""
M = 256
@tilelang.jit
def default_cast_kernel(M_val: int):
@T.prim_func
def main(
A: T.Tensor[(M_val,), "float32"], # noqa: F821
B: T.Tensor[(M_val,), "float8_e4m3fn"], # noqa: F821
):
with T.Kernel(1, threads=128):
A_local = T.alloc_fragment((M_val,), "float32")
B_local = T.alloc_fragment((M_val,), "float8_e4m3fn")
T.copy(A, A_local)
for i in T.Parallel(M_val):
B_local[i] = T.cast(A_local[i], "float8_e4m3fn")
T.copy(B_local, B)
return main
kernel = default_cast_kernel(M)
code = kernel.get_kernel_source()
assert "__nv_cvt_float2_to_fp8x2" in code, (
f"Default cast should use __nv_cvt_float2_to_fp8x2 for backward compatibility.\nGenerated code:\n{code}"
)
@tilelang.testing.requires_cuda
@tilelang.testing.requires_cuda_compute_version_ge(10, 0)
def test_cast_rs_codegen():
"""Test that round='rs' with rbits emits __tl_cvt_f32x4_to_e4m3x4_rs_sat."""
M = 256
@tilelang.jit
def cast_rs_kernel(M_val: int):
@T.prim_func
def main(
A: T.Tensor[(M_val,), "float32"], # noqa: F821
B: T.Tensor[(M_val,), "float8_e4m3fn"], # noqa: F821
):
with T.Kernel(1, threads=128):
A_local = T.alloc_fragment((M_val,), "float32")
B_local = T.alloc_fragment((M_val,), "float8_e4m3fn")
rbits = T.alloc_fragment((1,), "int32")
T.copy(A, A_local)
rbits[0] = T.cast(T.int32(0x12345678), "int32")
for i in T.Parallel(M_val):
B_local[i] = T.cast(A_local[i], "float8_e4m3fn", round="rs", rbits=rbits[0])
T.copy(B_local, B)
return main
kernel = cast_rs_kernel(M)
code = kernel.get_kernel_source()
# lanes=2 after vectorization -> uses x2 variant with zero-padding
assert "__tl_cvt_f32x2_to_e4m3x2_rs_sat" in code or "__tl_cvt_f32x4_to_e4m3x4_rs_sat" in code, (
f"Expected stochastic rounding helper in generated code.\nGenerated code:\n{code}"
)
# ===========================================================================
# Multi-lanes rs codegen tests (FP8 and FP4)
# ===========================================================================
@tilelang.jit
def _make_rs_kernel(M: int, num_threads: int, target_dtype: str):
@T.prim_func
def main(
A: T.Tensor[(M,), "float32"], # noqa: F821
B: T.Tensor[(M,), target_dtype], # noqa: F821
):
with T.Kernel(1, threads=num_threads):
A_local = T.alloc_fragment((M,), "float32")
B_local = T.alloc_fragment((M,), target_dtype)
rbits = T.alloc_fragment((1,), "int32")
T.copy(A, A_local)
rbits[0] = T.cast(T.int32(0x12345678), "int32")
for i in T.Parallel(M):
B_local[i] = T.cast(A_local[i], target_dtype, round="rs", rbits=rbits[0])
T.copy(B_local, B)
return main
@tilelang.testing.requires_cuda
@tilelang.testing.requires_cuda_compute_version_ge(10, 0)
@pytest.mark.parametrize(
"M,threads,expected",
[
(128, 128, "__tl_cvt_f32x1_to_e4m3x1_rs_sat"),
(256, 128, "__tl_cvt_f32x2_to_e4m3x2_rs_sat"),
(512, 128, "__tl_cvt_f32x4_to_e4m3x4_rs_sat"),
(1024, 128, "__tl_cvt_f32x4_to_e4m3x4_rs_sat"),
],
)
def test_cast_rs_fp8_lanes(M, threads, expected):
"""Test FP8 rs codegen across lanes=1,2,4,8."""
kernel = _make_rs_kernel(M, threads, "float8_e4m3fn")
code = kernel.get_kernel_source()
assert expected in code, f"Expected '{expected}' in generated code for M={M}, threads={threads}.\nGenerated code:\n{code}"
@tilelang.testing.requires_cuda
@tilelang.testing.requires_cuda_compute_version_ge(10, 0)
@pytest.mark.parametrize(
"M,threads,expected",
[
(128, 128, "__tl_cvt_f32x1_to_e2m1x1_rs_sat"),
(256, 128, "__tl_cvt_f32x2_to_e2m1x2_rs_sat"),
(512, 128, "__tl_cvt_f32x4_to_e2m1x4_rs_sat"),
(1024, 128, "__tl_cvt_f32x4_to_e2m1x4_rs_sat"),
],
)
def test_cast_rs_fp4_lanes(M, threads, expected):
"""Test FP4 rs codegen across lanes=1,2,4,8."""
kernel = _make_rs_kernel(M, threads, "float4_e2m1fn")
code = kernel.get_kernel_source()
assert expected in code, f"Expected '{expected}' in generated code for M={M}, threads={threads}.\nGenerated code:\n{code}"
# ===========================================================================
# rbits invariance -> chosen lane count
# ===========================================================================
#
# loop_vectorize.cc shrinks the cast vector size until the `rbits` operand
# is invariant across the chunk, so that one PTX cvt.rs.x{N} instruction can
# share a single rbits across N lanes. These tests pin that behaviour for
# the five rbits shapes that come up in practice.
@tilelang.jit
def _kernel_rbits_scalar(M: int, num_threads: int, target_dtype: str):
"""rbits = scalar fragment (loop-invariant) -> max lanes."""
@T.prim_func
def main(
A: T.Tensor[(M,), "float32"], # noqa: F821
B: T.Tensor[(M,), target_dtype], # noqa: F821
):
with T.Kernel(1, threads=num_threads):
A_local = T.alloc_fragment((M,), "float32")
B_local = T.alloc_fragment((M,), target_dtype)
rbits_scalar = T.alloc_fragment((1,), "int32")
T.copy(A, A_local)
rbits_scalar[0] = T.cast(T.int32(0x12345678), "int32")
for i in T.Parallel(M):
B_local[i] = T.cast(A_local[i], target_dtype, round="rs", rbits=rbits_scalar[0])
T.copy(B_local, B)
return main
@tilelang.jit
def _kernel_rbits_idiv4(M: int, num_threads: int, target_dtype: str):
"""rbits = rbits_buf[i // 4] -> shared across 4 lanes, expect x4."""
@T.prim_func
def main(
A: T.Tensor[(M,), "float32"], # noqa: F821
B: T.Tensor[(M,), target_dtype], # noqa: F821
):
with T.Kernel(1, threads=num_threads):
A_local = T.alloc_fragment((M,), "float32")
B_local = T.alloc_fragment((M,), target_dtype)
rbits_buf = T.alloc_fragment((M,), "int32")
T.copy(A, A_local)
for j in T.Parallel(M):
rbits_buf[j] = T.cast(0x11111111, "int32")
for i in T.Parallel(M):
B_local[i] = T.cast(A_local[i], target_dtype, round="rs", rbits=rbits_buf[i // 4])
T.copy(B_local, B)
return main
@tilelang.jit
def _kernel_rbits_idiv2(M: int, num_threads: int, target_dtype: str):
"""rbits = rbits_buf[i // 2] -> shared across 2 lanes, expect x2."""
@T.prim_func
def main(
A: T.Tensor[(M,), "float32"], # noqa: F821
B: T.Tensor[(M,), target_dtype], # noqa: F821
):
with T.Kernel(1, threads=num_threads):
A_local = T.alloc_fragment((M,), "float32")
B_local = T.alloc_fragment((M,), target_dtype)
rbits_buf = T.alloc_fragment((M,), "int32")
T.copy(A, A_local)
for j in T.Parallel(M):
rbits_buf[j] = T.cast(0x22222222, "int32")
for i in T.Parallel(M):
B_local[i] = T.cast(A_local[i], target_dtype, round="rs", rbits=rbits_buf[i // 2])
T.copy(B_local, B)
return main
@tilelang.jit
def _kernel_rbits_per_element(M: int, num_threads: int, target_dtype: str):
"""rbits = rbits_buf[i] (per-element) -> no sharing, expect x1."""
@T.prim_func
def main(
A: T.Tensor[(M,), "float32"], # noqa: F821
B: T.Tensor[(M,), target_dtype], # noqa: F821
):
with T.Kernel(1, threads=num_threads):
A_local = T.alloc_fragment((M,), "float32")
B_local = T.alloc_fragment((M,), target_dtype)
rbits_buf = T.alloc_fragment((M,), "int32")
T.copy(A, A_local)
for j in T.Parallel(M):
rbits_buf[j] = T.cast(0x33333333, "int32")
for i in T.Parallel(M):
B_local[i] = T.cast(A_local[i], target_dtype, round="rs", rbits=rbits_buf[i])
T.copy(B_local, B)
return main
@tilelang.jit
def _kernel_rbits_rng_rand(M: int, num_threads: int, target_dtype: str):
"""rbits = T.rng_rand() -> curand call carries side effects, expect x1.
Each lane needs its own random sample (PTX cvt.rs semantics shares one
rbits across the chunk, which is the *opposite* of what callers want
when they ask for fresh randomness per element). The vectorizer sees
the side effect and falls back to lanes=1.
"""
@T.prim_func
def main(
A: T.Tensor[(M,), "float32"], # noqa: F821
B: T.Tensor[(M,), target_dtype], # noqa: F821
):
with T.Kernel(1, threads=num_threads):
A_local = T.alloc_fragment((M,), "float32")
B_local = T.alloc_fragment((M,), target_dtype)
T.copy(A, A_local)
T.rng_init(42)
for i in T.Parallel(M):
B_local[i] = T.cast(A_local[i], target_dtype, round="rs", rbits=T.rng_rand())
T.copy(B_local, B)
return main
_RBITS_BUILDERS = {
"scalar": _kernel_rbits_scalar,
"idiv4": _kernel_rbits_idiv4,
"idiv2": _kernel_rbits_idiv2,
"per_element": _kernel_rbits_per_element,
"rng_rand": _kernel_rbits_rng_rand,
}
# Lane count is determined by rbits invariance, not by dtype, so fp8 and
# fp4 share the same expected lane table.
_RBITS_EXPECTED_LANES = {
"scalar": 4,
"idiv4": 4,
"idiv2": 2,
"per_element": 1,
"rng_rand": 1,
}
_DTYPE_HELPER_TAG = {
"float8_e4m3fn": "e4m3",
"float4_e2m1fn": "e2m1",
}
@tilelang.testing.requires_cuda
@tilelang.testing.requires_cuda_compute_version_ge(10, 0)
@pytest.mark.parametrize("dtype", ["float8_e4m3fn", "float4_e2m1fn"])
@pytest.mark.parametrize("rbits_mode", list(_RBITS_BUILDERS))
def test_cast_rs_rbits_invariance(rbits_mode, dtype):
"""rbits shape determines the chunk size of cvt.rs.x{N}."""
M, threads = 128, 32
builder = _RBITS_BUILDERS[rbits_mode]
kernel = builder(M, threads, dtype)
code = kernel.get_kernel_source()
n = _RBITS_EXPECTED_LANES[rbits_mode]
tag = _DTYPE_HELPER_TAG[dtype]
expected = f"__tl_cvt_f32x{n}_to_{tag}x{n}_rs_sat"
assert expected in code, f"Expected '{expected}' for rbits_mode={rbits_mode}, dtype={dtype}.\nGenerated code:\n{code}"
if __name__ == "__main__":
tilelang.testing.main()