Fuse Nemotron latent MoE projection and shared add (#30430)

Co-authored-by: Po-Han Huang (NVIDIA) <53919306+nvpohanh@users.noreply.github.com>
Co-authored-by: Mohammad Angkad <mohammad.angkad@radixark.ai>
Co-authored-by: Mohammad Miadh Angkad <176301910+mmangkad@users.noreply.github.com>
This commit is contained in:
Samuel Nordmann
2026-09-07 10:26:19 +08:00
committed by GitHub
co-authored by Po-Han Huang Mohammad Angkad Mohammad Miadh Angkad
parent 1d5d85260c
commit 214313ee79
4 changed files with 430 additions and 10 deletions
@@ -0,0 +1,205 @@
"""
Unit tests for UnquantizedLinearMethod.apply_with_addend.
The cuBLAS route folds the addend into the GEMM beta input,
writing back into that buffer; every other route must add separately
and leave the caller's buffer intact.
"""
from sglang.test.ci.ci_register import register_cuda_ci
register_cuda_ci(est_time=25, stage="base-b", runner_config="1-gpu-small")
import unittest
from contextlib import ExitStack
from unittest.mock import patch
import torch
import torch.nn.functional as F
import sglang.srt.layers.quantization.unquant as unquant
from sglang.srt.layers.linear import ReplicatedLinear
from sglang.test.test_utils import CustomTestCase
# addmm rounds once in the accumulator where the separate add rounds twice;
# with 8 BF16 mantissa bits the paths agree only to this precision.
_BF16_RTOL = 1e-2
_BF16_ATOL = 3.125e-2
def _cublas_only_backend():
# The TORCH backend leaves every custom-kernel global unpopulated.
return patch.object(unquant, "_BF16_GEMM_BACKEND", unquant.Bf16GemmBackend.TORCH)
def _fake_kernel(calls, name):
def kernel(x, weight, bias=None, *args):
calls.append(name)
return F.linear(x, weight, bias)
return kernel
@unittest.skipUnless(torch.cuda.is_available(), "CUDA is required")
class TestApplyWithAddend(CustomTestCase):
def setUp(self):
torch.manual_seed(0)
self.projection = ReplicatedLinear(
64, 128, bias=False, params_dtype=torch.bfloat16
).cuda()
self.projection.weight.copy_(
torch.randn_like(self.projection.weight) / 8.0 # 1 / sqrt(64)
)
self.method = self.projection.quant_method
def _reference(self, x, addend, bias=None):
return F.linear(x, self.projection.weight, bias) + addend
@torch.inference_mode()
def test_cublas_route_accumulates_into_addend(self):
with _cublas_only_backend():
x = torch.randn(16, 64, device="cuda", dtype=torch.bfloat16)
addend = torch.randn(16, 128, device="cuda", dtype=torch.bfloat16)
reference = self._reference(x, addend)
output = self.method.apply_with_addend(self.projection, x, addend)
self.assertEqual(output.data_ptr(), addend.data_ptr())
torch.testing.assert_close(
output, reference, rtol=_BF16_RTOL, atol=_BF16_ATOL
)
@torch.inference_mode()
def test_cuda_graph_replay_reads_the_replayed_addend(self):
"""A graph replay must consume the addend written on that replay;
addmm(out=addend) reads and writes the one buffer."""
with _cublas_only_backend():
x = torch.randn(16, 64, device="cuda", dtype=torch.bfloat16)
produced = torch.randn(16, 128, device="cuda", dtype=torch.bfloat16)
# Initialize the cuBLAS workspace before capture.
self.method.apply_with_addend(self.projection, x, produced.clone())
torch.cuda.synchronize()
graph = torch.cuda.CUDAGraph()
with torch.cuda.graph(graph):
# clone() stands in for the shared expert,
# which rewrites its output buffer on every replay.
captured = self.method.apply_with_addend(
self.projection, x, produced.clone()
)
x.copy_(torch.randn_like(x))
produced.copy_(torch.randn_like(produced))
reference = self._reference(x, produced)
graph.replay()
torch.cuda.synchronize()
torch.testing.assert_close(
captured, reference, rtol=_BF16_RTOL, atol=_BF16_ATOL
)
@torch.inference_mode()
def test_batch_invariant_mode_keeps_separate_add(self):
"""Deterministic inference must not reach the fused route;
batch-invariant mode does not override aten::addmm.out."""
with (
_cublas_only_backend(),
patch.object(unquant, "is_batch_invariant_mode_enabled", return_value=True),
):
x = torch.randn(4, 64, device="cuda", dtype=torch.bfloat16)
addend = torch.randn(4, 128, device="cuda", dtype=torch.bfloat16)
before = addend.clone()
output = self.method.apply_with_addend(self.projection, x, addend)
self.assertNotEqual(output.data_ptr(), addend.data_ptr())
torch.testing.assert_close(addend, before, rtol=0, atol=0)
torch.testing.assert_close(
output, self._reference(x, before), rtol=_BF16_RTOL, atol=_BF16_ATOL
)
@torch.inference_mode()
def test_unfused_routes_leave_the_addend_intact(self):
"""Every route that cannot use the GEMM beta input adds separately;
consuming the addend there corrupts the caller's buffer."""
for route in (
"non_nvidia",
"compiling",
"cutedsl",
"splitk",
"hopper_gemv",
"noncontiguous_addend",
"bias",
):
with self.subTest(route=route):
self._assert_route_is_unfused(route)
def _assert_route_is_unfused(self, route: str):
x = torch.randn(4, 64, device="cuda", dtype=torch.bfloat16)
addend = (
torch.randn(128, 4, device="cuda", dtype=torch.bfloat16).t()
if route == "noncontiguous_addend"
else torch.randn(4, 128, device="cuda", dtype=torch.bfloat16)
)
bias = (
torch.randn(128, device="cuda", dtype=torch.bfloat16)
if route == "bias"
else None
)
before = addend.clone()
kernel_calls = []
with ExitStack() as stack:
enter = stack.enter_context
enter(_cublas_only_backend())
if route == "non_nvidia":
enter(patch.object(unquant, "_is_cuda", False))
elif route == "compiling":
enter(patch.object(torch.compiler, "is_compiling", return_value=True))
elif route == "cutedsl":
enter(patch.object(unquant, "_use_cutedsl_bf16_gemm", lambda *a: True))
enter(
patch.object(
unquant,
"_cutedsl_bf16_gemm",
_fake_kernel(kernel_calls, route),
)
)
elif route == "splitk":
enter(patch.object(unquant, "_enable_bf16_splitk_gemm", True))
enter(
patch.object(
unquant, "use_flashinfer_pr4266_bf16_gemm", lambda *a: True
)
)
enter(
patch.object(
unquant,
"_flashinfer_pr4266_bf16_gemm",
_fake_kernel(kernel_calls, route),
)
)
elif route == "hopper_gemv":
enter(patch.object(unquant, "_use_hopper_bf16_gemv", lambda *a: True))
enter(
patch.object(
unquant,
"_hopper_bf16_gemv",
_fake_kernel(kernel_calls, route),
)
)
output = self.method.apply_with_addend(self.projection, x, addend, bias)
self.assertNotEqual(output.data_ptr(), addend.data_ptr())
torch.testing.assert_close(addend, before, rtol=0, atol=0)
torch.testing.assert_close(
output, self._reference(x, before, bias), rtol=_BF16_RTOL, atol=_BF16_ATOL
)
if route in ("cutedsl", "splitk", "hopper_gemv"):
self.assertEqual(kernel_calls, [route])
if __name__ == "__main__":
unittest.main()