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submission 158766

snowclipsed · python · License unknown

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No package. Vendor the mirrored source: 165 lines, June 9 Researcher Reciprocity License v1.0.

gemm_tma.py
curl "https://kernelindex.com/api/v1/implementations/kernelbot-nvfp4-gemm-158766?include=source"
interfacepython
Compatibility
measured onNVIDIA B200
declared hardwareNVIDIA B200
architecturessm_100
dtypesfp8_e4m3, nvfp4

Benchmark evidence

1 measurement across 1 GPU, fastest first.

Operation / workload
Hardware
Latency
Rank
Observed
NVFP4 GEMMsuite of 3 cases
NVIDIA B200
11.4µs
#88 of 369
2025-12-15

Reported · How evidence levels are derived →

Source and license

sourceavailable
revision digestsha256:dd1d66fed39775d3861ab42d9d866769247bdf4686e01db25e1b75582813cf4f
license declaredunknown
license concludedunknown
authorssnowclipsed
imported2026-08-15

Techniques

Extracted from the mirrored source by pattern, never inferred. Each row cites its line.

clusterusing ClusterShape = Shape<_1, _2, _1>;
fp4using ElementA = cutlass::nv_float4_t<cutlass::float_e2m1_t>;
fused-epilogueusing ElementCompute = cutlass::half_t; // Use half for epilogue compute
warp-specializationusing KernelSchedule = cutlass::gemm::KernelTmaWarpSpecialized1SmNvf4Sm100;

Kernel source

gemm_tma.py165 lines
import torch
from torch.utils.cpp_extension import load_inline
import os

input_t = tuple
output_t = torch.Tensor

cuda_source = r'''
#include <torch/extension.h>
#include <cuda_runtime.h>
#include "cutlass/cutlass.h"
#include "cute/tensor.hpp"
#include "cutlass/gemm/dispatch_policy.hpp"
#include "cutlass/gemm/collective/collective_builder.hpp"
#include "cutlass/epilogue/collective/collective_builder.hpp"
#include "cutlass/detail/sm100_blockscaled_layout.hpp"
#include "cutlass/gemm/device/gemm_universal_adapter.h"
#include "cutlass/gemm/kernel/gemm_universal.hpp"
#include "cutlass/util/packed_stride.hpp"

using namespace cute;

#if defined(CUTLASS_ARCH_MMA_SM100_SUPPORTED)

using ElementA = cutlass::nv_float4_t<cutlass::float_e2m1_t>;
using LayoutATag = cutlass::layout::RowMajor;
constexpr int AlignmentA = 64;

using ElementB = cutlass::nv_float4_t<cutlass::float_e2m1_t>;
using LayoutBTag = cutlass::layout::ColumnMajor;
constexpr int AlignmentB = 64;

using ElementD = cutlass::half_t;
using ElementC = void;
using LayoutCTag = cutlass::layout::RowMajor;
using LayoutDTag = cutlass::layout::RowMajor;
constexpr int AlignmentD = 16;
constexpr int AlignmentC = 1;

using ElementAccumulator = float;
using ElementCompute = cutlass::half_t;  // Use half for epilogue compute

using ArchTag = cutlass::arch::Sm100;
using OperatorClass = cutlass::arch::OpClassBlockScaledTensorOp;

using MmaTileShape = Shape<_128, _64, _256>;
using ClusterShape = Shape<_1, _2, _1>;

using KernelSchedule = cutlass::gemm::KernelTmaWarpSpecialized1SmNvf4Sm100;
using EpilogueSchedule = cutlass::epilogue::NoSmemWarpSpecialized1Sm;

using CollectiveEpilogue = typename cutlass::epilogue::collective::CollectiveBuilder<
    ArchTag, OperatorClass,
    MmaTileShape, ClusterShape,
    cutlass::epilogue::collective::EpilogueTileAuto,
    ElementAccumulator, ElementCompute,
    ElementC, LayoutCTag, AlignmentC,
    ElementD, LayoutDTag, AlignmentD,
    EpilogueSchedule
>::CollectiveOp;

using CollectiveMainloop = typename cutlass::gemm::collective::CollectiveBuilder<
    ArchTag, OperatorClass,
    ElementA, LayoutATag, AlignmentA,
    ElementB, LayoutBTag, AlignmentB,
    ElementAccumulator,
    MmaTileShape, ClusterShape,
    cutlass::gemm::collective::StageCountAutoCarveout<
        static_cast<int>(sizeof(typename CollectiveEpilogue::SharedStorage))>,
    KernelSchedule
>::CollectiveOp;

using GemmKernel = cutlass::gemm::kernel::GemmUniversal<
    Shape<int, int, int, int>,
    CollectiveMainloop,
    CollectiveEpilogue,
    void>;

using Gemm = cutlass::gemm::device::GemmUniversalAdapter<GemmKernel>;
using StrideA = typename Gemm::GemmKernel::StrideA;
using StrideB = typename Gemm::GemmKernel::StrideB;
using StrideD = typename Gemm::GemmKernel::StrideD;
using LayoutSFA = typename Gemm::GemmKernel::CollectiveMainloop::LayoutSFA;
using LayoutSFB = typename Gemm::GemmKernel::CollectiveMainloop::LayoutSFB;
using Sm1xxBlkScaledConfig = typename Gemm::GemmKernel::CollectiveMainloop::Sm1xxBlkScaledConfig;

void nvfp4_gemm(
    torch::Tensor a, torch::Tensor b,
    torch::Tensor sfa_perm, torch::Tensor sfb_perm,
    torch::Tensor c, int m, int n, int k, int l)
{
    StrideA stride_A = cutlass::make_cute_packed_stride(StrideA{}, {m, k, l});
    StrideB stride_B = cutlass::make_cute_packed_stride(StrideB{}, {n, k, l});
    StrideD stride_D = cutlass::make_cute_packed_stride(StrideD{}, {m, n, l});

    LayoutSFA layout_SFA = Sm1xxBlkScaledConfig::tile_atom_to_shape_SFA(cute::make_shape(m, n, k, l));
    LayoutSFB layout_SFB = Sm1xxBlkScaledConfig::tile_atom_to_shape_SFB(cute::make_shape(m, n, k, l));

    typename Gemm::Arguments arguments{
        cutlass::gemm::GemmUniversalMode::kGemm,
        {m, n, k, l},
        {reinterpret_cast<typename ElementA::DataType*>(a.data_ptr()), stride_A,
         reinterpret_cast<typename ElementB::DataType*>(b.data_ptr()), stride_B,
         reinterpret_cast<typename ElementA::ScaleFactorType*>(sfa_perm.data_ptr()), layout_SFA,
         reinterpret_cast<typename ElementB::ScaleFactorType*>(sfb_perm.data_ptr()), layout_SFB},
        {{cutlass::half_t(1.0f), cutlass::half_t(0.0f)}, nullptr, {}, 
         reinterpret_cast<ElementD*>(c.data_ptr()), stride_D}
    };

    Gemm gemm;
    size_t workspace_size = Gemm::get_workspace_size(arguments);
    auto workspace = torch::empty({static_cast<long>(workspace_size)}, 
        torch::TensorOptions().dtype(torch::kUInt8).device(a.device()));

    gemm.initialize(arguments, workspace.data_ptr());
    gemm.run();
}

#else
void nvfp4_gemm(torch::Tensor, torch::Tensor, torch::Tensor, torch::Tensor,
                torch::Tensor, int, int, int, int) {
    TORCH_CHECK(false, "SM100 not supported");
}
#endif

PYBIND11_MODULE(TORCH_EXTENSION_NAME, m) {
    m.def("nvfp4_gemm", &nvfp4_gemm, "NVFP4 GEMM");
}
'''

cpp_source = """
#include <torch/extension.h>
void nvfp4_gemm(torch::Tensor a, torch::Tensor b,
                torch::Tensor sfa_perm, torch::Tensor sfb_perm,
                torch::Tensor c, int m, int n, int k, int l);
"""

cutlass_path = os.environ.get("CUTLASS_PATH", "/usr/local/cutlass")
cuda_include = os.environ.get("CUDA_INCLUDE_DIR", "/usr/local/cuda/include")

module = load_inline(
    name="nvfp4_gemm_module",
    cpp_sources=[cpp_source],
    cuda_sources=[cuda_source],
    extra_include_paths=[
        f"{cutlass_path}/include",
        f"{cutlass_path}/tools/util/include",
        cuda_include,
    ],
    extra_cuda_cflags=[
        "-std=c++17",
        "-arch=sm_100a",
        "-DCUTLASS_ARCH_MMA_SM100_SUPPORTED=1",
        "-O3",
        "--use_fast_math",
    ],
    verbose=False,
)

def custom_kernel(data: input_t) -> output_t:
    a, b, sfa, sfb, sfa_perm, sfb_perm, c = data
    m, n, l = c.shape[0], c.shape[1], c.shape[2]
    k = a.shape[1] * 2
    module.nvfp4_gemm(a, b, sfa_perm, sfb_perm, c, m, n, k, l)
    return c
scrolls · 165 lines total

Source code from GPU Mode and the KernelBot dataset · June 9 Researcher Reciprocity License v1.0

Changes from previous submission

Against this author's previous submission submission 158340.

⋯ 9 unchanged lines
#include <cuda_runtime.h>
#include "cutlass/cutlass.h"
#include "cute/tensor.hpp"
- #include "cutlass/tensor_ref.h"
#include "cutlass/gemm/dispatch_policy.hpp"
#include "cutlass/gemm/collective/collective_builder.hpp"
#include "cutlass/epilogue/collective/collective_builder.hpp"
⋯ 6 unchanged lines
#if defined(CUTLASS_ARCH_MMA_SM100_SUPPORTED)
- // NVFP4 with float_ue4m3_t scale factors (VS=16, block16)
using ElementA = cutlass::nv_float4_t<cutlass::float_e2m1_t>;
using LayoutATag = cutlass::layout::RowMajor;
- constexpr int AlignmentA = 32;
+ constexpr int AlignmentA = 64;
using ElementB = cutlass::nv_float4_t<cutlass::float_e2m1_t>;
using LayoutBTag = cutlass::layout::ColumnMajor;
- constexpr int AlignmentB = 32;
+ constexpr int AlignmentB = 64;
using ElementD = cutlass::half_t;
- using ElementC = void; // No bias matrix - pure D = A*B
+ using ElementC = void;
using LayoutCTag = cutlass::layout::RowMajor;
using LayoutDTag = cutlass::layout::RowMajor;
constexpr int AlignmentD = 16;
- constexpr int AlignmentC = 1; // void type
+ constexpr int AlignmentC = 1;
using ElementAccumulator = float;
+ using ElementCompute = cutlass::half_t; // Use half for epilogue compute
+
using ArchTag = cutlass::arch::Sm100;
using OperatorClass = cutlass::arch::OpClassBlockScaledTensorOp;
using MmaTileShape = Shape<_128, _64, _256>;
using ClusterShape = Shape<_1, _2, _1>;
- using KernelSchedule = cutlass::gemm::KernelTmaWarpSpecialized1SmNvf4Sm100;
+ using KernelSchedule = cutlass::gemm::KernelTmaWarpSpecialized1SmNvf4Sm100;
using EpilogueSchedule = cutlass::epilogue::NoSmemWarpSpecialized1Sm;
using CollectiveEpilogue = typename cutlass::epilogue::collective::CollectiveBuilder<
ArchTag, OperatorClass,
MmaTileShape, ClusterShape,
cutlass::epilogue::collective::EpilogueTileAuto,
- ElementAccumulator, ElementAccumulator,
+ ElementAccumulator, ElementCompute,
ElementC, LayoutCTag, AlignmentC,
ElementD, LayoutDTag, AlignmentD,
EpilogueSchedule
⋯ 17 unchanged lines
void>;
using Gemm = cutlass::gemm::device::GemmUniversalAdapter<GemmKernel>;
-
using StrideA = typename Gemm::GemmKernel::StrideA;
using StrideB = typename Gemm::GemmKernel::StrideB;
using StrideD = typename Gemm::GemmKernel::StrideD;
⋯ 1 unchanged lines
using LayoutSFB = typename Gemm::GemmKernel::CollectiveMainloop::LayoutSFB;
using Sm1xxBlkScaledConfig = typename Gemm::GemmKernel::CollectiveMainloop::Sm1xxBlkScaledConfig;
- // Cached state for repeated calls
- static thread_local Gemm* cached_gemm = nullptr;
- static thread_local void* cached_workspace = nullptr;
- static thread_local int cached_m = 0, cached_n = 0, cached_k = 0, cached_l = 0;
- static thread_local StrideA cached_stride_A;
- static thread_local StrideB cached_stride_B;
- static thread_local StrideD cached_stride_D;
- static thread_local LayoutSFA cached_layout_SFA;
- static thread_local LayoutSFB cached_layout_SFB;
-
void nvfp4_gemm(
torch::Tensor a, torch::Tensor b,
torch::Tensor sfa_perm, torch::Tensor sfb_perm,
torch::Tensor c, int m, int n, int k, int l)
{
- bool dims_changed = (m != cached_m || n != cached_n || k != cached_k || l != cached_l);
-
- if (dims_changed || cached_gemm == nullptr) {
- cached_stride_A = cutlass::make_cute_packed_stride(StrideA{}, {m, k, l});
- cached_stride_B = cutlass::make_cute_packed_stride(StrideB{}, {n, k, l});
- cached_stride_D = cutlass::make_cute_packed_stride(StrideD{}, {m, n, l});
- cached_layout_SFA = Sm1xxBlkScaledConfig::tile_atom_to_shape_SFA(cute::make_shape(m, n, k, l));
- cached_layout_SFB = Sm1xxBlkScaledConfig::tile_atom_to_shape_SFB(cute::make_shape(m, n, k, l));
- }
+ StrideA stride_A = cutlass::make_cute_packed_stride(StrideA{}, {m, k, l});
+ StrideB stride_B = cutlass::make_cute_packed_stride(StrideB{}, {n, k, l});
+ StrideD stride_D = cutlass::make_cute_packed_stride(StrideD{}, {m, n, l});
- auto* a_ptr = reinterpret_cast<typename ElementA::DataType*>(a.data_ptr());
- auto* b_ptr = reinterpret_cast<typename ElementB::DataType*>(b.data_ptr());
- auto* sfa_ptr = reinterpret_cast<typename ElementA::ScaleFactorType*>(sfa_perm.data_ptr());
- auto* sfb_ptr = reinterpret_cast<typename ElementB::ScaleFactorType*>(sfb_perm.data_ptr());
- auto* d_ptr = reinterpret_cast<ElementD*>(c.data_ptr());
+ LayoutSFA layout_SFA = Sm1xxBlkScaledConfig::tile_atom_to_shape_SFA(cute::make_shape(m, n, k, l));
+ LayoutSFB layout_SFB = Sm1xxBlkScaledConfig::tile_atom_to_shape_SFB(cute::make_shape(m, n, k, l));
typename Gemm::Arguments arguments{
cutlass::gemm::GemmUniversalMode::kGemm,
{m, n, k, l},
- {a_ptr, cached_stride_A, b_ptr, cached_stride_B, sfa_ptr, cached_layout_SFA, sfb_ptr, cached_layout_SFB},
- {{1.0f, 0.0f}, nullptr, {}, d_ptr, cached_stride_D}
+ {reinterpret_cast<typename ElementA::DataType*>(a.data_ptr()), stride_A,
+ reinterpret_cast<typename ElementB::DataType*>(b.data_ptr()), stride_B,
+ reinterpret_cast<typename ElementA::ScaleFactorType*>(sfa_perm.data_ptr()), layout_SFA,
+ reinterpret_cast<typename ElementB::ScaleFactorType*>(sfb_perm.data_ptr()), layout_SFB},
+ {{cutlass::half_t(1.0f), cutlass::half_t(0.0f)}, nullptr, {},
+ reinterpret_cast<ElementD*>(c.data_ptr()), stride_D}
};
-
- if (dims_changed || cached_gemm == nullptr) {
- delete cached_gemm;
- cached_gemm = new Gemm();
-
- size_t workspace_size = Gemm::get_workspace_size(arguments);
- if (workspace_size > 0) {
- cudaMalloc(&cached_workspace, workspace_size);
- } else {
- cached_workspace = nullptr;
- }
-
- auto status = cached_gemm->initialize(arguments, cached_workspace);
- TORCH_CHECK(status == cutlass::Status::kSuccess,
- "CUTLASS init failed: ", cutlass::cutlassGetStatusString(status));
-
- cached_m = m; cached_n = n; cached_k = k; cached_l = l;
- } else {
- auto status = cached_gemm->update(arguments, cached_workspace);
- TORCH_CHECK(status == cutlass::Status::kSuccess,
- "CUTLASS update failed: ", cutlass::cutlassGetStatusString(status));
- }
- auto status = cached_gemm->run();
- TORCH_CHECK(status == cutlass::Status::kSuccess,
- "CUTLASS run failed: ", cutlass::cutlassGetStatusString(status));
+ Gemm gemm;
+ size_t workspace_size = Gemm::get_workspace_size(arguments);
+ auto workspace = torch::empty({static_cast<long>(workspace_size)},
+ torch::TensorOptions().dtype(torch::kUInt8).device(a.device()));
+
+ gemm.initialize(arguments, workspace.data_ptr());
+ gemm.run();
}
#else
- void nvfp4_gemm(torch::Tensor a, torch::Tensor b,
- torch::Tensor sfa_perm, torch::Tensor sfb_perm,
- torch::Tensor c, int m, int n, int k, int l) {
+ void nvfp4_gemm(torch::Tensor, torch::Tensor, torch::Tensor, torch::Tensor,
+ torch::Tensor, int, int, int, int) {
TORCH_CHECK(false, "SM100 not supported");
}
#endif
⋯ 27 unchanged lines
"-arch=sm_100a",
"-DCUTLASS_ARCH_MMA_SM100_SUPPORTED=1",
"-O3",
+ "--use_fast_math",
],
verbose=False,
)
def custom_kernel(data: input_t) -> output_t:
a, b, sfa, sfb, sfa_perm, sfb_perm, c = data
- m = int(c.shape[0])
- n = int(c.shape[1])
- l = int(c.shape[2])
- k = int(a.shape[1] * 2)
+ m, n, l = c.shape[0], c.shape[1], c.shape[2]
+ k = a.shape[1] * 2
module.nvfp4_gemm(a, b, sfa_perm, sfb_perm, c, m, n, k, l)
return c
No newline at end of file
scrolls · 178 diff lines total

Best evidence level for this revision: reported

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