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2026-07-13 12:55:37 +08:00

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Python

# SPDX-License-Identifier: Apache-2.0
# SPDX-FileCopyrightText: Copyright contributors to the vLLM project
"""Tests for CPU INT4 W4A8 dynamic quantized fused MoE kernel (CPUExpertsInt4)."""
import sys
import pytest
import torch
import torch.nn.functional as F
from vllm.model_executor.layers.fused_moe.activation import MoEActivation
from vllm.model_executor.layers.fused_moe.experts.cpu_int4_moe import (
CPUExpertsInt4,
)
from vllm.model_executor.layers.fused_moe.oracle.w4a8_int8 import (
convert_to_w4a8_int8_moe_format,
)
from vllm.platforms import CpuArchEnum, current_platform
from vllm.utils.torch_utils import set_random_seed
if (
not current_platform.is_cpu()
or current_platform.get_cpu_architecture() != CpuArchEnum.ARM
):
pytest.skip("skipping Arm CPU-only tests", allow_module_level=True)
# Tolerance for INT4 W4A8
INT4_W4A8_ATOL = 2e-2
INT4_W4A8_RTOL = 2e-2
def _silu_and_mul(x: torch.Tensor) -> torch.Tensor:
"""SwiGLU activation: SiLU(gate) * up."""
d = x.shape[-1] // 2
return F.silu(x[..., :d]) * x[..., d:]
def _make_int4_moe_weights(
E: int,
N: int,
K: int,
group_size: int,
has_bias: bool = False,
) -> tuple[
torch.Tensor,
torch.Tensor,
torch.Tensor,
torch.Tensor,
torch.Tensor | None,
torch.Tensor | None,
]:
"""Generate random INT4 MoE weights with random scales.
Args:
E: Number of experts
N: Intermediate size
K: Hidden size
group_size: Quantization group size (-1 for channel-wise)
has_bias: Whether to include bias
Returns:
(w13_packed, w2_packed, w13_ref, w2_ref, w13_bias, w2_bias)
where *_ref are the dequantized float reference weights
"""
# Generate INT4 weights as int8 values in [-8, 7]
w13_int4 = torch.randint(-8, 8, (E, 2 * N, K), dtype=torch.int8)
w2_int4 = torch.randint(-8, 8, (E, K, N), dtype=torch.int8)
# Determine number of scale columns
def _n_scale_cols(in_features: int) -> int:
return 1 if group_size == -1 else (in_features // group_size)
# Generate random scales
scale_dtype = torch.float32 if group_size == -1 else torch.bfloat16
w13_scales = torch.rand(E, 2 * N, _n_scale_cols(K), dtype=scale_dtype) * 0.01
w2_scales = torch.rand(E, K, _n_scale_cols(N), dtype=scale_dtype) * 0.01
# Generate biases if needed
w13_bias = None
w2_bias = None
if has_bias:
w13_bias = torch.randn(E, 2 * N, dtype=torch.float32) * 0.01
w2_bias = torch.randn(E, K, dtype=torch.float32) * 0.01
w13_packed, w2_packed, *_ = convert_to_w4a8_int8_moe_format(
w13_weight=w13_int4,
w2_weight=w2_int4,
w13_weight_scale=w13_scales,
w2_weight_scale=w2_scales,
group_size=group_size,
w13_bias=w13_bias if has_bias else None,
w2_bias=w2_bias if has_bias else None,
)
if group_size == -1:
w13_scale = w13_scales.float()
w2_scale = w2_scales.float()
else:
w13_scale = w13_scales.float().repeat_interleave(group_size, dim=-1)
w2_scale = w2_scales.float().repeat_interleave(group_size, dim=-1)
w13_ref = w13_int4.float() * w13_scale
w2_ref = w2_int4.float() * w2_scale
if has_bias and w13_bias is not None:
w13_ref = w13_ref + w13_bias.float().unsqueeze(-1)
if has_bias and w2_bias is not None:
w2_ref = w2_ref + w2_bias.float().unsqueeze(-1)
return w13_packed, w2_packed, w13_ref, w2_ref, w13_bias, w2_bias
def ref_int4_moe(
a: torch.Tensor,
w13_ref: torch.Tensor,
w2_ref: torch.Tensor,
topk_weight: torch.Tensor,
topk_ids: torch.Tensor,
) -> torch.Tensor:
"""Reference INT4 W4A8 fused MoE using dequantized weights.
Steps:
1. Use dequantized float weights
2. For each expert: matmul → SwiGLU → matmul
3. Weighted sum across top-k experts
"""
B, D = a.shape
topk = topk_ids.size(1)
a_exp = a.view(B, -1, D).repeat(1, topk, 1).reshape(-1, D).float()
out = torch.zeros(B * topk, w2_ref.shape[1], dtype=torch.float32)
topk_weight_flat = topk_weight.view(-1)
topk_ids_flat = topk_ids.view(-1)
for i in range(w13_ref.shape[0]):
mask = topk_ids_flat == i
if mask.sum():
# w13: [2N, K], input: [B, K] -> output: [B, 2N]
gate_up = torch.matmul(a_exp[mask], w13_ref[i].transpose(0, 1))
# SwiGLU activation
hidden = _silu_and_mul(gate_up)
# w2: [K, N], hidden: [B, N] -> output: [B, K]
out[mask] = torch.matmul(hidden, w2_ref[i].transpose(0, 1))
return (
(out.view(B, -1, w2_ref.shape[1]) * topk_weight_flat.view(B, -1, 1))
.sum(dim=1)
.to(a.dtype)
)
NUM_TOKENS = [1, 2, 64, 128]
# (intermediate_size N, hidden_size K, num_experts E, topk, group_size)
MoE_CONFIGS = [
(256, 512, 8, 2, 128),
(256, 512, 8, 2, 64),
(256, 512, 8, 2, -1), # channel-wise
(512, 256, 8, 4, 128),
(512, 512, 8, 2, 128),
(768, 2048, 8, 2, 128),
(768, 2048, 16, 4, 64),
]
SEEDS = [0, 42]
ACTIVATION_DTYPES = [torch.float32, torch.bfloat16, torch.float16]
@pytest.mark.parametrize("M", NUM_TOKENS)
@pytest.mark.parametrize("N,K,E,topk,group_size", MoE_CONFIGS)
@pytest.mark.parametrize("seed", SEEDS)
@pytest.mark.parametrize("activation_dtype", ACTIVATION_DTYPES)
def test_cpu_int4_moe_kernel(M, N, K, E, topk, group_size, seed, activation_dtype):
"""Test dynamic_4bit_int_moe kernel against dequantized torch reference."""
set_random_seed(seed)
activation = MoEActivation.SILU
# Generate input activations
a = torch.randn(M, K, dtype=activation_dtype) / (K**0.5)
# Generate INT4 weights
w13_packed, w2_packed, w13_ref, w2_ref, w13_bias, w2_bias = _make_int4_moe_weights(
E, N, K, group_size, has_bias=False
)
# Generate router logits and topk
score = torch.randn(M, E, dtype=torch.bfloat16)
score = torch.softmax(score, dim=-1, dtype=torch.float32)
topk_weight, topk_ids = torch.topk(score, topk)
topk_ids = topk_ids.to(torch.long)
# Reference output using dequantized weights
ref_out = ref_int4_moe(
a,
w13_ref,
w2_ref,
topk_weight,
topk_ids,
)
# Test dynamic_4bit_int_moe kernel
apply_router_weight_on_input = False
out = torch.ops._C.dynamic_4bit_int_moe(
a,
topk_ids,
topk_weight,
w13_packed,
w2_packed,
K, # H (hidden_size / w2_out_features)
N, # I (intermediate_size / w2_in_features)
group_size,
apply_router_weight_on_input,
CPUExpertsInt4._activation_kind(activation),
)
assert out.dtype == activation_dtype
torch.testing.assert_close(
ref_out,
out,
atol=INT4_W4A8_ATOL,
rtol=INT4_W4A8_RTOL,
)
if __name__ == "__main__":
sys.exit(pytest.main([__file__, "-v"]))