[Bugfix] Fix test fused quant layernorm tests (vllm-project#27865)

Signed-off-by: ElizaWszola <ewszola@redhat.com>
Signed-off-by: yewentao256 <zhyanwentao@126.com>
Co-authored-by: yewentao256 <zhyanwentao@126.com>
Co-authored-by: Wentao Ye <44945378+yewentao256@users.noreply.github.com>

Author: ElizaWszola

csrc/quantization/w8a8/int8/scaled_quant.cu

@@ -1,5 +1,6 @@
 #include <ATen/cuda/CUDAContext.h>
 #include <torch/all.h>
+#include <c10/cuda/CUDAGuard.h>
 
 #include <cmath>
 
@@ -275,6 +276,7 @@ void static_scaled_int8_quant(torch::Tensor& out,          // [..., hidden_size]
   int const num_tokens = input.numel() / hidden_size;
   dim3 const grid(num_tokens);
   dim3 const block(std::min(hidden_size, 256));
+  const at::cuda::OptionalCUDAGuard device_guard(device_of(input));
   const cudaStream_t stream = at::cuda::getCurrentCUDAStream();
   VLLM_DISPATCH_FLOATING_TYPES(
       input.scalar_type(), "static_scaled_int8_quant_kernel", [&] {
@@ -306,6 +308,7 @@ void dynamic_scaled_int8_quant(
   int const num_tokens = input.numel() / hidden_size;
   dim3 const grid(num_tokens);
   dim3 const block(std::min(hidden_size, 256));
+  const at::cuda::OptionalCUDAGuard device_guard(device_of(input));
   const cudaStream_t stream = at::cuda::getCurrentCUDAStream();
   VLLM_DISPATCH_FLOATING_TYPES(
       input.scalar_type(), "dynamic_scaled_int8_quant_kernel", [&] {

tests/kernels/core/test_fused_quant_layernorm.py

@@ -11,7 +11,7 @@
 
 DTYPES = [torch.bfloat16, torch.float]
 QUANT_DTYPES = [torch.int8, torch.float8_e4m3fn]
-VEC_HIDDEN_SIZES = range(1024, 1030)
+VEC_HIDDEN_SIZES = [1024, 1025, 1027, 1029]
 # Avoid combinatorial explosion with full Cartesian product
 NUM_TOKENS_HIDDEN_SIZES = [
     *[(1, i) for i in [1, 64, *VEC_HIDDEN_SIZES, 5120, 5137]],
@@ -65,7 +65,7 @@ def ref_dynamic_per_token_quant(
         )
     else:
         assert quant_dtype == torch.int8
-        torch_out, scales = ops.scaled_int8_quant(torch_out)
+        torch_out, scales, _ = ops.scaled_int8_quant(torch_out)
 
     return torch_out, scales, residual
 
@@ -109,7 +109,7 @@ def ops_impl(
 
 @pytest.mark.parametrize("num_tokens, hidden_size", NUM_TOKENS_HIDDEN_SIZES)
 @pytest.mark.parametrize("add_residual", ADD_RESIDUAL)
-@pytest.mark.parametrize("scale_ub", SCALE_UBS)
+@pytest.mark.parametrize("has_scale_ub", SCALE_UBS)
 @pytest.mark.parametrize("dtype", DTYPES)
 @pytest.mark.parametrize("quant_dtype", QUANT_DTYPES)
 @pytest.mark.parametrize("seed", SEEDS)
@@ -119,7 +119,7 @@ def test_rms_norm(
     num_tokens: int,
     hidden_size: int,
     add_residual: bool,
-    scale_ub: bool,
+    has_scale_ub: bool,
     dtype: torch.dtype,
     quant_dtype: torch.dtype,
     seed: int,
@@ -130,7 +130,7 @@ def test_rms_norm(
         torch.cuda.manual_seed(seed)
     torch.set_default_device(device)
 
-    if scale_ub is not None and quant_dtype != torch.float8_e4m3fn:
+    if has_scale_ub and quant_dtype != torch.float8_e4m3fn:
         # skip
         return
 
@@ -143,9 +143,11 @@ def test_rms_norm(
     scale = 1 / (hidden_size)
     x = torch.randn(num_tokens, hidden_size, dtype=dtype) * scale
     residual = torch.randn_like(x) * scale if add_residual else None
-    if scale_ub is not None:
+    if has_scale_ub:
         rms_x, _ = ref_rms_norm(layer, x, residual)
         scale_ub = torch.mean(rms_x).to(dtype=torch.float32, device="cuda")
+    else:
+        scale_ub = None
 
     ref_out, ref_scales, ref_residual = ref_impl(
         layer, x, quant_dtype, residual, scale_ub
@@ -156,14 +158,27 @@ def test_rms_norm(
 
     assert ref_out.dtype == quant_dtype
     assert ops_out.dtype == quant_dtype
-    assert torch.allclose(ref_scales, ops_scales)
     if quant_dtype == torch.int8:
+        assert torch.allclose(ref_scales, ops_scales, atol=1e-6)
         # big atol to account for round-off errors.
         assert torch.allclose(ref_out, ops_out, atol=1)
     else:
-        assert torch.allclose(
-            ref_out.to(dtype=torch.float32), ops_out.to(dtype=torch.float32)
-        )
+        assert torch.allclose(ref_scales, ops_scales)
+        a = ref_out.to(dtype=torch.float32)
+        b = ops_out.to(dtype=torch.float32)
+        ok = torch.allclose(a, b)
+        if not ok:
+            # fallback: compare dequantized values with relaxed tolerance
+            a_deq = a * ref_scales.view(-1, 1)
+            b_deq = b * ops_scales.view(-1, 1)
+            # NOTE: It is possible that some future test cases trigger this
+            # max diff due to precision issues. If such an error is
+            # encountered, it's recommended to inspect the differences between
+            # all corresponding elements from each tensor (e.g. by looping over
+            # them) and checking how many the max diff error shows up on (just
+            # a few bad elements should still be considered acceptable).
+            ok = torch.allclose(a_deq, b_deq, rtol=5e-2, atol=5e-2)
+        assert ok
     if add_residual:
         assert torch.allclose(ref_residual, ops_residual)