gpt-5.5-priority · original · l123_single_gpt
compile_fail 15_Matmul_for_lower_triangular_matrices.py
model
gpt-5.5-priority
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tool calls
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wall clock
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truncated
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backend
cuda fp32
variant
original
runtime
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speedup
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started
2026-05-05T00:04:41Z
compile error: Error building extension 'lower_triangular_trmm_ext_v1': [1/2] /opt/conda/bin/x86_64-conda-linux-gnu-c++ -MMD -MF main.o.d -DTORCH_EXTENSION_NAME=lower_triangular_trmm_ext_v1 -DTORCH_API_INCLUDE_EXTENSION_H -isystem /scratch/abaner/KernelBench/.venv/lib/python3.10/site-packages/torch/include -isystem /scratch/abaner/KernelBench/.venv/lib/python3.10/site-packages/torch/include/torch/csrc/api/include -isystem /usr/local/cuda/include -isystem /opt/conda/include/python3.10 -fPIC -std=c++17 -O3 -c /scratch/abaner/KernelBench/runs/l123_single_gpt/original/gpt-5.5-priority/level_1_problem_15_cache/k_
timingkernelbench.timing
kernel runtime
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ref runtime
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speedup
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kernel mean / median / std
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ref mean / median / std
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reference PyTorch source (the prompt the agent sees)
import torch
import torch.nn as nn

class Model(nn.Module):
    """
    Simple model that performs a matrix multiplication (C = A * B) where A and B are lower triangular matrices. 
    """
    def __init__(self):
        super(Model, self).__init__()
    
    def forward(self, A, B):
        """
        Performs matrix multiplication of lower triangular matrices A and B.

        Args:
            A (torch.Tensor): Lower triangular matrix of shape (N, N).
            B (torch.Tensor): Lower triangular matrix of shape (N, N).

        Returns:
            torch.Tensor: The result of matrix multiplication C of shape (N, N).
        """
        return torch.tril(torch.matmul(A, B))

M = 4096

def get_inputs():
    A = torch.rand(M, M)
    B = torch.rand(M, M)
    A = torch.tril(A)
    B = torch.tril(B)
    return [A, B]

def get_init_inputs():
    return []  # No special initialization inputs needed
turn 0 · FINAL · 1 tool call(s) · 178.5s turn · 178.5s LLM · 9,369 chars (click to expand)
turn 0178.5s turn · 178.5s LLM · 0.0s tools · FINAL
reasoning
**Evaluating TF32 and FP32 differences** I'm trying to figure out if there's a notable difference between TF32 errors and exact comparisons. It seems FP32 could be a bit too high, like relative 1e-3. I need to check if PyTorch is using the default settings for TF32 and ensure the reference matches the expected tolerances — usually 1e-4 for FP32. I should confirm if cublasStrmm is available and ensure that things like with_cuda=True are correctly set up in the build parameters. Maybe I'll explore if custom kernels will fit the requirements. **Considering performance options** I'm trying to figure out how to use both triangular matrices effectively, aiming for N^3/6 performance. It seems like there might be a challenge, especially since the performance of custom simple tiled FP32 CUDA cores is lower than what I’d get with cuBLAS. I wonder how to optimize this better. Do I need to rethink my approach or maybe adjust my strategy to improve performance? There’s definitely a lot to consider here! **Calculating tile performance** I’m working through some calculations related to tile design. The total number of tiles sums up to about 2.83 million, which is equivalent to 11.6 billion fused multiply-add (FMA) operations. Each 16x16 block seems to have 256 threads, running around 85 iterations, so we're looking at about 1,360 FMA per tile. I’m considering shared loads and register occupancy; performance should be moderate. There’s also redundancy in using __syncthreads, which could lead to overhead. Lastly, I’m pondering block configurations for optimal performance. **Evaluating CUDA integration** I'm considering whether to include the cublas host in the cuda_sources. If I'm using cublas, it seems like I can't have a custom kernel. I'm thinking of including a custom zero for the upper output, but then I hesitate. Maybe I'll add a custom kernel and choose cublasStrmm in my wrapper. Ultimately, my goal is to see if cublasStrmm produces the exact upper zeros I need. Let's clarify that! **Evaluating matrix computations** I’m looking into how lower entries might compute the sum of B_col(r,k)*A_col(k,c) for k. It seems with upper triangular matrices, I need to consider conditions like r > c and if k satisfies r <= k <= c. I might skip structural terms if necessary, and I wonder if cublas will write the lower part properly. It's good that cublas TRMM should ideally compute and write the full C matrix. If there's a speed issue, I could consider using a custom kernel. Finally, ensuring my output is in JSON format with one tool call is crucial. **Considering handle optimization** I’m thinking about potential name collisions in caching across submissions, and it might be best to use unique names. I could optimize the handle creation overhead by instantiating it during the first forward, but that could make the cublasCreate overhead quite significant. Maybe I can create a handle at module load through a function. I should define an init_cublas() that can be called after load_inline in Python to set up the handle before timing. This could include a guard to manage device contexts effectively and minimize overhead during evaluations. **Optimizing handle management** Alright, if there are multiple static handles, I’ll need to associate them with device 0, especially since matrix A is on device 0 too. I should confirm if the cublas handle can be linked to the device. If I initialize it before any device settings, that should default to device 0, which is fine. I also want to ensure my initialization step is in place. I need to check if the PyTorch timing accurately reflects the module load, as that compilation might not be measured.
call → submit_kernel
callsubmit_kernel { "kernel_code": "import torch\nimport torch.nn as nn\nfrom torch.utils.cpp_extension import load_inline\n\n_cpp_src = r'''\n#include <torch/extension.h>\n#include <ATen/cuda/CUDAContext.h>\n#include <c10/cuda/CUDAGuard.h>\n#include <cublas_v2.h>\n#include <mutex>\n\nstatic cublasHandle_t g_handle = nullptr;\nstatic std::once_flag g_handle_once;\n\nstatic void create_handle_once() {\n CUBLAS_CHECK(cublasCreate(&g_handle));\n // Use standard fp32 math for numerical agreement with torch fp32 matmul.\n CUBLAS_CHECK(cublasSetMathMode(g_handle, CUBLAS_DEFAULT_MATH));\n}\n\nstatic cublasHandle_t get_handle() {\n std::call_once(g_handle_once, create_handle_once);\n return g_handle;\n}\n\nvoid init_cublas() {\n c10::cuda::CUDAGuard device_guard(0);\n (void)get_handle();\n}\n\ntorch::Tensor tri_matmul(torch::Tensor A, torch::Tensor B) {\n const int64_t n64 = A.size(0);\n const int n = static_cast<int>(n64);\n\n c10::cuda::CUDAGuard device_guard(A.device());\n auto C = torch::empty_like(A);\n\n cublasHandle_t handle = get_handle();\n CUBLAS_CHECK(cublasSetStream(handle, at::cuda::getCurrentCUDAStream(A.get_device())));\n\n const float alpha = 1.0f;\n\n // PyTorch tensors are row-major. Interpreting the same storage as\n // column-major transposes each matrix. For C_row = A_row * B_row,\n // we compute C_col = B_col * A_col = B_row^T * A_row^T.\n // A_col is upper triangular because A_row is lower triangular.\n CUBLAS_CHECK(cublasStrmm(\n handle,\n CUBLAS_SIDE_RIGHT,\n CUBLAS_FILL_MODE_UPPER,\n CUBLAS_OP_N,\n CUBLAS_DIAG_NON_UNIT,\n n, n,\n &alpha,\n A.data_ptr<float>(), n,\n B.data_ptr<float>(), n,\n C.data_ptr<float>(), n));\n\n return C;\n}\n'''\n\n_ext = load_inline(\n name='lower_triangular_trmm_ext_v1',\n cpp_sources=_cpp_src,\n functions=['tri_matmul', 'init_cublas'],\n with_cuda=True,\n extra_cflags=['-O3'],\n extra_ldflags=['-lcublas'],\n verbose=False,\n)\n\n# Pay one-time cuBLAS handle creation outside the measured forward path.\n_ext.init_cublas()\n\nclass ModelNew(nn.Module):\n def __init__(self):\n super(ModelNew, self).__init__()\n\n def forward(self, A, B):\n return _ext.tri_matmul(A, B)\n" }
result ← submit_kernel (fail)
failsubmit_kernel submit_kernel FAILED: kernel did not compile. Error building extension 'lower_triangular_trmm_ext_v1': [1/2] /opt/conda/bin/x86_64-conda-linux-gnu-c++ -MMD -MF main.o.d -DTORCH_EXTENSION_NAME=lower_triangular_trmm_ext_v1 -DTORCH_API_INCLUDE_EXTENSION_H -isystem /scratch/abaner/KernelBench/.venv/lib/python3.10/site-packages/torch/include -isystem /scratch/abaner/KernelBench/.venv/lib/python3.10/site-packages/torch/include/torch/csrc/api/include -isystem /usr/local/cuda/include -isystem /opt/conda/include/python3.10 -fPIC -std=c++17 -O3 -c /scratch/abaner/KernelBench/runs/l123_single_gpt/original/gpt-5.5-priority/level_1_problem_15_cache/k_f69a6daf7d76/lower_triangular_trmm_ext_v1/main.cpp -o main.o FAILED: [code=1] main.o /opt/conda/bin/x86_64-conda-linux-gnu-c++ -MMD -MF main.o.d -DTORCH_EXTENSION_NAME=lower_triangular_trmm_ext_v1 -DTORCH_API_INCLUDE_EXTENSION_H -isystem /scratch/abaner/KernelBench/.venv/lib/python3.10/site-packages/torch/include -isystem /scratch/abaner/KernelBench/.venv/lib/python3.10/site-packages/torch/include/torch/csrc/api/include -isystem /usr/local/cuda/include -isystem /opt/conda/include/python3.10 -fPIC -std=c++17 -O3 -c /scratch/abaner/KernelBench/runs/l123_single_gpt/original/gpt-5.5-priority/level_1_problem_15_cache/k_f69a6daf7d76/lower_triangular_trmm_ext_v1/main.cpp -o main.o /scratch/abaner/KernelBench/runs/l123_single_gpt/original/gpt-5.5-priority/level_1_problem_15_cache/k_f69a6daf7d76/lower_triangular_trmm_ext_v1/main.cpp: In function 'void create_handle_once()': /scratch/abaner/KernelBench/runs/l123_single_gpt/original/gpt-5.5-priority/level_1_problem_15_cache/k_f69a6daf7d76/lower_triangular_trmm_ext_v1/main.cpp:13:5: error: 'CUBLAS_CHECK' was not declared in this scope; did you mean 'CUBLAS_OP_C'? 13 | CUBLAS_CHECK(cublasCreate(&g_handle)); | ^~~~~~~~~~~~ | CUBLAS_OP_C /scratch/abaner/KernelBench/runs/l123_single_gpt/original/gpt-5.5-priority/level_1_problem_15_cache/k_f69a6daf7d76/lower_triangular_trmm_ext_v1/main.cpp: In function 'at::Tensor tri_matmul(at::Tensor, at::Tensor)': /scratch/abaner/KernelBench/runs/l123_single_gpt/original/gpt-5.5-priority/level_1_problem_15_cache/k_f69a6daf7d76/lower_triangular_trmm_ext_v1/main.cpp:36:5: error: 'CUBLAS_CHECK' was not declared in this scope; did you mean 'CUBLAS_OP_C'? 36 | CUBLAS_CHECK(cublasSetStream(handle, at::cuda::getCurrentCUDAStream(A.get_device()))); | ^~~~~~~~~~~~ | CUBLAS_OP_C ninja: build stopped: subcommand failed.
final submitted kernel (82 lines, 2,205 chars) — full source, untruncated
import torch
import torch.nn as nn
from torch.utils.cpp_extension import load_inline

_cpp_src = r'''
#include <torch/extension.h>
#include <ATen/cuda/CUDAContext.h>
#include <c10/cuda/CUDAGuard.h>
#include <cublas_v2.h>
#include <mutex>

static cublasHandle_t g_handle = nullptr;
static std::once_flag g_handle_once;

static void create_handle_once() {
    CUBLAS_CHECK(cublasCreate(&g_handle));
    // Use standard fp32 math for numerical agreement with torch fp32 matmul.
    CUBLAS_CHECK(cublasSetMathMode(g_handle, CUBLAS_DEFAULT_MATH));
}

static cublasHandle_t get_handle() {
    std::call_once(g_handle_once, create_handle_once);
    return g_handle;
}

void init_cublas() {
    c10::cuda::CUDAGuard device_guard(0);
    (void)get_handle();
}

torch::Tensor tri_matmul(torch::Tensor A, torch::Tensor B) {
    const int64_t n64 = A.size(0);
    const int n = static_cast<int>(n64);

    c10::cuda::CUDAGuard device_guard(A.device());
    auto C = torch::empty_like(A);

    cublasHandle_t handle = get_handle();
    CUBLAS_CHECK(cublasSetStream(handle, at::cuda::getCurrentCUDAStream(A.get_device())));

    const float alpha = 1.0f;

    // PyTorch tensors are row-major.  Interpreting the same storage as
    // column-major transposes each matrix.  For C_row = A_row * B_row,
    // we compute C_col = B_col * A_col = B_row^T * A_row^T.
    // A_col is upper triangular because A_row is lower triangular.
    CUBLAS_CHECK(cublasStrmm(
        handle,
        CUBLAS_SIDE_RIGHT,
        CUBLAS_FILL_MODE_UPPER,
        CUBLAS_OP_N,
        CUBLAS_DIAG_NON_UNIT,
        n, n,
        &alpha,
        A.data_ptr<float>(), n,
        B.data_ptr<float>(), n,
        C.data_ptr<float>(), n));

    return C;
}
'''

_ext = load_inline(
    name='lower_triangular_trmm_ext_v1',
    cpp_sources=_cpp_src,
    functions=['tri_matmul', 'init_cublas'],
    with_cuda=True,
    extra_cflags=['-O3'],
    extra_ldflags=['-lcublas'],
    verbose=False,
)

# Pay one-time cuBLAS handle creation outside the measured forward path.
_ext.init_cublas()

class ModelNew(nn.Module):
    def __init__(self):
        super(ModelNew, self).__init__()

    def forward(self, A, B):
        return _ext.tri_matmul(A, B)