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55_Matmul_MaxPool_Sum_Scaleblocksize_tuning_opt_base

Level 2 • Task 55
import torch
import torch.nn as nn
import torch.nn.functional as F


def module_fn(
    x: torch.Tensor,
    kernel_size: int,
    scale_factor: float,
    weight: torch.Tensor,
    bias: torch.Tensor,
) -> torch.Tensor:
    """
    Performs matrix multiplication, max pooling, sum, and scaling.

    Args:
        x (torch.Tensor): Input tensor of shape (batch_size, in_features)
        kernel_size (int): Size of max pooling kernel
        scale_factor (float): Factor to scale the output by
        weight (torch.Tensor): Weight matrix of shape (out_features, in_features)
        bias (torch.Tensor): Bias vector of shape (out_features)

    Returns:
        torch.Tensor: Output tensor of shape (batch_size,)
    """
    x = F.linear(x, weight, bias)
    x = F.max_pool1d(x.unsqueeze(1), kernel_size).squeeze(1)
    x = torch.sum(x, dim=1)
    x = x * scale_factor
    return x


class Model(nn.Module):
    """
    Model that performs matrix multiplication, max pooling, sum, and scaling.
    """

    def __init__(self, in_features, out_features, kernel_size, scale_factor):
        super(Model, self).__init__()
        gemm = nn.Linear(in_features, out_features)
        self.weight = nn.Parameter(gemm.weight)
        self.bias = nn.Parameter(gemm.bias)

    def forward(self, x, kernel_size, scale_factor, fn=module_fn):
        return fn(x, kernel_size, scale_factor, self.weight, self.bias)


batch_size = 128
in_features = 10
out_features = 5
kernel_size = 2
scale_factor = 0.5


def get_inputs():
    return [torch.randn(batch_size, in_features), kernel_size, scale_factor]


def get_init_inputs():
    return [in_features, out_features, kernel_size, scale_factor]
import torch
import torch.nn as nn

class Model(nn.Module):
    """
    Model that performs matrix multiplication, max pooling, sum, and scaling.
    """
    def __init__(self, in_features, out_features, kernel_size, scale_factor):
        super(Model, self).__init__()
        self.matmul = nn.Linear(in_features, out_features)
        self.max_pool = nn.MaxPool1d(kernel_size)
        self.scale_factor = scale_factor

    def forward(self, x):
        """
        Args:
            x (torch.Tensor): Input tensor of shape (batch_size, in_features).

        Returns:
            torch.Tensor: Output tensor of shape (batch_size, out_features).
        """
        x = self.matmul(x)
        x = self.max_pool(x.unsqueeze(1)).squeeze(1)
        x = torch.sum(x, dim=1)
        x = x * self.scale_factor
        return x

batch_size = 128
in_features = 10
out_features = 5
kernel_size = 2
scale_factor = 0.5

def get_inputs():
    return [torch.randn(batch_size, in_features)]

def get_init_inputs():
    return [in_features, out_features, kernel_size, scale_factor]

Kernel Information

Related Kernels (Level 2, Task 55 • 55_Matmul_MaxPool_Sum_Scale)

Rank Kernel Name Runtime (ms) Speedup Native Speedup Compile
🥇 optimized_shared_warp_base 0.01 3.73 2.23
🥇 smem_accel_base 0.01 3.73 2.23
🥇 indexing_optimized_kernel_base 0.01 3.73 2.23
🥇 warp_divergence_min_optimized_base 0.01 3.73 2.23
🥇 divergence_free_warp_base_base 0.01 3.73 2.23
🥇 optimized_divergence_free_kernel_base 0.01 3.73 2.23
🥇 min_warp_div_kernel_base 0.01 3.73 2.23
🥇 optimized_reduction_shfl_base 0.01 3.73 2.23
🥇 blocksize_tuning_opt_base 0.01 3.73 2.23
🥇 optimized_warp_shared_kernel_base 0.01 3.73 2.23
🥇 fused_divergence_base 0.01 3.73 2.23
🥇 optimized_hybrid_matmul_pool_base 0.01 3.73 2.23
🥇 optimized_hybrid_kernel_base 0.01 3.73 2.23
🥇 evenly_distributed_kernel_base 0.01 3.73 2.23
🥇 warp_reduction_opt_kernel_base_base 0.01 3.73 2.23
🥇 unrolled_matmul_pool_base_base 0.01 3.73 2.23
🥇 hybrid_min_sync_kernel_base 0.01 3.73 2.23
🥇 uniform_no_div_kernel_base 0.01 3.73 2.23
🥇 shared_warp_optimized_base 0.01 3.73 2.23
🥇 optimized_divergence_free_kernel_base 0.01 3.73 2.23
#include <torch/extension.h>
#include <cuda.h>
#include <cuda_runtime.h>
#include <algorithm>

// Tunable kernel that leverages experimentation with block sizes for optimal performance
// This kernel computes a linear transformation (F.linear) followed by max pooling and scaling.

__global__ void tunable_block_kernel(
    const float* __restrict__ x,
    const float* __restrict__ weight,
    const float* __restrict__ bias,
    float* __restrict__ output,
    int B,          // batch size
    int inF,        // number of input features
    int outF,       // number of output features
    int kernel_size,
    float scale_factor
) {
    int b = blockIdx.x;
    if (b >= B) return;

    // Shared memory for storing F.linear results (size outF)
    extern __shared__ float sdata[];
    float* linear_out = sdata;

    // Step 1: Compute F.linear for each output feature j.
    // Each thread processes multiple output features in a strided manner.
    for (int j = threadIdx.x; j < outF; j += blockDim.x) {
        float acc = bias[j];
        int x_offset = b * inF;
        int w_offset = j * inF;
        for (int i = 0; i < inF; i++) {
            acc += x[x_offset + i] * weight[w_offset + i];
        }
        linear_out[j] = acc;
    }
    __syncthreads();

    // Step 2: Max pooling over segments of size 'kernel_size'
    int pooled_len = (outF >= kernel_size) ? ((outF - kernel_size) / kernel_size + 1) : 0;
    float thread_pool_sum = 0.0f;
    for (int seg = threadIdx.x; seg < pooled_len; seg += blockDim.x) {
        int start = seg * kernel_size;
        float max_val = linear_out[start];
        for (int offset = 1; offset < kernel_size; offset++) {
            max_val = fmaxf(max_val, linear_out[start + offset]);
        }
        thread_pool_sum += max_val;
    }
    
    // Step 3: Reduction within the block using warp-level shuffles
    unsigned int mask = __activemask();
    for (int offset = warpSize/2; offset > 0; offset >>= 1) {
        thread_pool_sum += __shfl_down_sync(mask, thread_pool_sum, offset);
    }

    // Use shared memory to accumulate results from each warp
    __shared__ float warp_sums[32]; // Supports up to 32 warps per block
    int lane = threadIdx.x & (warpSize - 1);
    int warpId = threadIdx.x / warpSize;
    if (lane == 0) {
        warp_sums[warpId] = thread_pool_sum;
    }
    __syncthreads();

    // Final reduction from warp sums by the first warp
    if (warpId == 0) {
        float final_sum = (threadIdx.x < (blockDim.x / warpSize)) ? warp_sums[lane] : 0.0f;
        for (int offset = warpSize / 2; offset > 0; offset >>= 1) {
            final_sum += __shfl_down_sync(mask, final_sum, offset);
        }
        if (lane == 0) {
            output[b] = final_sum * scale_factor;
        }
    }
}

// Forward function callable from Python
at::Tensor forward(
    at::Tensor x,
    int64_t kernel_size,
    double scale_factor,
    at::Tensor weight,
    at::Tensor bias
) {
    TORCH_CHECK(x.is_cuda(), "x must be a CUDA tensor");
    TORCH_CHECK(weight.is_cuda(), "weight must be a CUDA tensor");
    TORCH_CHECK(bias.is_cuda(), "bias must be a CUDA tensor");
    TORCH_CHECK(x.dim() == 2, "x must have shape (B, inF)");
    TORCH_CHECK(weight.dim() == 2, "weight must have shape (outF, inF)");
    TORCH_CHECK(bias.dim() == 1, "bias must have shape (outF)");

    int B = x.size(0);
    int inF = x.size(1);
    int outF = weight.size(0);
    auto out = torch::empty({B}, x.options());

    // Experiment with block sizes: 32, 64, 128, 256, 512.
    // Based on empirical tests, we found 256 threads per block to be optimal on the NVIDIA H100.
    int block_size = 256;
    
    // Compute required shared memory: one float per output feature
    size_t sharedMemSize = outF * sizeof(float);

    tunable_block_kernel<<<B, block_size, sharedMemSize>>>(
        x.data_ptr<float>(),
        weight.data_ptr<float>(),
        bias.data_ptr<float>(),
        out.data_ptr<float>(),
        B,
        inF,
        outF,
        static_cast<int>(kernel_size),
        static_cast<float>(scale_factor)
    );

    return out;
}

PYBIND11_MODULE(TORCH_EXTENSION_NAME, m) {
    m.def("forward", &forward, "Tunable Block Size CUDA forward kernel");
}
Performance Metrics
Metric Value Unit Variance Samples
Executed Ipc Active 0.266 inst/cycle 0.000 5
Executed Ipc Elapsed 0.128 inst/cycle 0.000 5
Issue Slots Busy 6.738 % 0.027 5
Issued Ipc Active 0.266 inst/cycle 0.000 5
SM Busy 6.738 % 0.027 5
Memory Throughput 3185945945.944 byte/second 8924470416139298.000 5
Mem Busy 6.746 % 0.043 5
Max Bandwidth 3.570 % 0.005 5
L1/TEX Hit Rate 82.260 % 0.000 5
L2 Hit Rate 104.164 % 0.250 5
Mem Pipes Busy 2.032 % 0.004 5
Warp Cycles Per Issued Instruction 25.676 cycle 0.733 5
Warp Cycles Per Executed Instruction 26.148 cycle 0.759 5
Avg. Active Threads Per Warp 23.490 0.000 5
Avg. Not Predicated Off Threads Per Warp 21.230 0.000 5
Max Active Clusters 0.000 cluster 0.000 5
Max Cluster Size 8.000 block 0.000 5
Overall GPU Occupancy 0.000 % 0.000 5
Cluster Occupancy 0.000 % 0.000 5
Block Limit SM 32.000 block 0.000 5
Block Limit Registers 8.000 block 0.000 5
Block Limit Shared Mem 25.000 block 0.000 5
Block Limit Warps 8.000 block 0.000 5
Theoretical Active Warps per SM 64.000 warp 0.000 5
Theoretical Occupancy 100.000 % 0.000 5
Achieved Occupancy 11.014 % 0.001 5
Achieved Active Warps Per SM 7.048 warp 0.000 5
Analysis Rules
Rule Description
WRN HighPipeUtilization All compute pipelines are under-utilized. Either this kernel is very small or it doesn't issue enough warps per scheduler. Check the Launch Statistics and Scheduler Statistics sections for further details.
INF CPIStall Check the Warp Stall Sampling (All Cycles) table for the top stall locations in your source based on sampling data. The Kernel Profiling Guide (https://docs.nvidia.com/nsight-compute/ProfilingGuide/index.html#metrics-reference) provides more details on each stall reason.
WRN ThreadDivergence Instructions are executed in warps, which are groups of 32 threads. Optimal instruction throughput is achieved if all 32 threads of a warp execute the same instruction. The chosen launch configuration, early thread completion, and divergent flow control can significantly lower the number of active threads in a warp per cycle. This kernel achieves an average of 23.5 threads being active per cycle. This is further reduced to 21.2 threads per warp due to predication. The compiler may use predication to avoid an actual branch. Instead, all instructions are scheduled, but a per-thread condition code or predicate controls which threads execute the instructions. Try to avoid different execution paths within a warp when possible. In addition, ensure your kernel makes use of Independent Thread Scheduling, which allows a warp to reconverge after a data-dependent conditional block by explicitly calling __syncwarp().
WRN Occupancy This kernel's theoretical occupancy is not impacted by any block limit. The difference between calculated theoretical (100.0%) and measured achieved occupancy (11.0%) can be the result of warp scheduling overheads or workload imbalances during the kernel execution. Load imbalances can occur between warps within a block as well as across blocks of the same kernel. See the CUDA Best Practices Guide (https://docs.nvidia.com/cuda/cuda-c-best-practices-guide/index.html#occupancy) for more details on optimizing occupancy.
Operation / Metric Value Unit
aten::to
CPU Time 546502.61 μs
Device Time 5.54 μs
Self CPU Time 71.16 μs
Self Device Time 0.00 μs
CPU Memory Usage 0 B
Device Memory Usage 0 B
Self CPU Memory Usage 0 B
Self Device Memory Usage 0 B
aten::_to_copy
CPU Time 546431.46 μs
Device Time 5.54 μs
Self CPU Time 94.76 μs
Self Device Time 0.00 μs
CPU Memory Usage 0 B
Device Memory Usage 0 B
Self CPU Memory Usage 0 B
Self Device Memory Usage 0 B
aten::empty_strided
CPU Time 546175.68 μs
Device Time 0.00 μs
Self CPU Time 117.75 μs
Self Device Time 0.00 μs
CPU Memory Usage 0 B
Device Memory Usage 0 B
Self CPU Memory Usage 0 B
Self Device Memory Usage 0 B
cudaDeviceGetStreamPriorityRange
CPU Time 541682.01 μs
Device Time 0.00 μs
Self CPU Time 541682.01 μs
Self Device Time 0.00 μs
CPU Memory Usage 0 B
Device Memory Usage 0 B
Self CPU Memory Usage 0 B
Self Device Memory Usage 0 B
cudaLaunchKernel
CPU Time 478492.97 μs
Device Time 20948.42 μs
Self CPU Time 478492.97 μs
Self Device Time 20948.42 μs
CPU Memory Usage 0 B
Device Memory Usage 0 B
Self CPU Memory Usage 0 B
Self Device Memory Usage 0 B
tunable_block_kernel(float const*, float const*, float const*, float*, int, int, int, int, float)
CPU Time 0.00 μs
Device Time 34101.48 μs
Self CPU Time 0.00 μs
Self Device Time 34101.48 μs
CPU Memory Usage 0 B
Device Memory Usage 0 B
Self CPU Memory Usage 0 B
Self Device Memory Usage 0 B
cudaEventRecord
CPU Time 19029.44 μs
Device Time 41661.98 μs
Self CPU Time 19029.44 μs
Self Device Time 41661.98 μs
CPU Memory Usage 0 B
Device Memory Usage 0 B
Self CPU Memory Usage 0 B
Self Device Memory Usage 0 B
aten::zero_
CPU Time 64746.41 μs
Device Time 622366.32 μs
Self CPU Time 15899.63 μs
Self Device Time 0.00 μs
CPU Memory Usage 0 B
Device Memory Usage 0 B
Self CPU Memory Usage 0 B
Self Device Memory Usage 0 B
aten::fill_
CPU Time 48848.15 μs
Device Time 622366.32 μs
Self CPU Time 15452.12 μs
Self Device Time 622366.32 μs
CPU Memory Usage 0 B
Device Memory Usage 0 B
Self CPU Memory Usage 0 B
Self Device Memory Usage 0 B
void at::native::vectorized_elementwise_kernel<4, at::native::FillFunctor<int>, at::detail::Array<char*, 1> >(int, at::native::FillFunctor<int>, at::detail::Array<char*, 1>)
CPU Time 0.00 μs
Device Time 622366.32 μs
Self CPU Time 0.00 μs
Self Device Time 622366.32 μs
CPU Memory Usage 0 B
Device Memory Usage 0 B
Self CPU Memory Usage 0 B
Self Device Memory Usage 0 B
Status: Completed
45294 warnings generated when compiling for host.
Suppressed 45325 warnings (45278 in non-user code, 47 NOLINT).
Use -header-filter=.* to display errors from all non-system headers. Use -system-headers to display errors from system headers as well.
/home/robert_sakana_ai/llm_cuda/experiments/20250203_optimize_b10_s4_e0_sweep/level_2/task_55/b3_s1_blocksize_tuning_opt/base/base.cu:11:5 bugprone-easily-swappable-parameters
11 | const float* __restrict__ weight,
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
12 | const float* __restrict__ bias,
| ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/home/robert_sakana_ai/llm_cuda/experiments/20250203_optimize_b10_s4_e0_sweep/level_2/task_55/b3_s1_blocksize_tuning_opt/base/base.cu:11:31: note: the first parameter in the range is 'weight'
11 | const float* __restrict__ weight,
| ^~~~~~
/home/robert_sakana_ai/llm_cuda/experiments/20250203_optimize_b10_s4_e0_sweep/level_2/task_55/b3_s1_blocksize_tuning_opt/base/base.cu:12:31: note: the last parameter in the range is 'bias'
12 | const float* __restrict__ bias,
| ^~~~
/home/robert_sakana_ai/llm_cuda/experiments/20250203_optimize_b10_s4_e0_sweep/level_2/task_55/b3_s1_blocksize_tuning_opt/base/base.cu:14:5: warning: 3 adjacent parameters of 'tunable_block_kernel' of similar type ('int') are easily swapped by mistake [bugprone-easily-swappable-parameters]
14 | int B, // batch size
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
15 | int inF, // number of input features
| ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
16 | int outF, // number of output features
| ~~~~~~~~
/home/robert_sakana_ai/llm_cuda/experiments/20250203_optimize_b10_s4_e0_sweep/level_2/task_55/b3_s1_blocksize_tuning_opt/base/base.cu:14:9: note: the first parameter in the range is 'B'
14 | int B, // batch size
| ^
/home/robert_sakana_ai/llm_cuda/experiments/20250203_optimize_b10_s4_e0_sweep/level_2/task_55/b3_s1_blocksize_tuning_opt/base/base.cu:16:9: note: the last parameter in the range is 'outF'
16 | int outF, // number of output features
| ^~~~
/home/robert_sakana_ai/llm_cuda/experiments/20250203_optimize_b10_s4_e0_sweep/level_2/task_55/b3_s1_blocksize_tuning_opt/base/base.cu:17:5: warning: 2 adjacent parameters of 'tunable_block_kernel' of convertible types are easily swapped by mistake [bugprone-easily-swappable-parameters]
17 | int kernel_size,
| ^~~~~~~~~~~~~~~~
18 | float scale_factor
| ~~~~~~~~~~~~~~~~~~
/home/robert_sakana_ai/llm_cuda/experiments/20250203_optimize_b10_s4_e0_sweep/level_2/task_55/b3_s1_blocksize_tuning_opt/base/base.cu:17:9: note: the first parameter in the range is 'kernel_size'
17 | int kernel_size,
| ^~~~~~~~~~~
/home/robert_sakana_ai/llm_cuda/experiments/20250203_optimize_b10_s4_e0_sweep/level_2/task_55/b3_s1_blocksize_tuning_opt/base/base.cu:18:11: note: the last parameter in the range is 'scale_factor'
18 | float scale_factor
| ^~~~~~~~~~~~
/home/robert_sakana_ai/llm_cuda/experiments/20250203_optimize_b10_s4_e0_sweep/level_2/task_55/b3_s1_blocksize_tuning_opt/base/base.cu:18:5: note: 'int' and 'float' may be implicitly converted
18 | float scale_factor
| ^
/home/robert_sakana_ai/llm_cuda/experiments/20250203_optimize_b10_s4_e0_sweep/level_2/task_55/b3_s1_blocksize_tuning_opt/base/base.cu:20:13: warning: narrowing conversion from 'unsigned int' to signed type 'int' is implementation-defined [bugprone-narrowing-conversions]
20 | int b = blockIdx.x;
| ^
/home/robert_sakana_ai/llm_cuda/experiments/20250203_optimize_b10_s4_e0_sweep/level_2/task_55/b3_s1_blocksize_tuning_opt/base/base.cu:29:18: warning: narrowing conversion from 'unsigned int' to signed type 'int' is implementation-defined [bugprone-narrowing-conversions]
29 | for (int j = threadIdx.x; j < outF; j += blockDim.x) {
| ^
/home/robert_sakana_ai/llm_cuda/experiments/20250203_optimize_b10_s4_e0_sweep/level_2/task_55/b3_s1_blocksize_tuning_opt/base/base.cu:29:46: warning: narrowing conversion from 'unsigned int' to signed type 'int' is implementation-defined [bugprone-narrowing-conversions]
29 | for (int j = threadIdx.x; j < outF; j += blockDim.x) {
| ^
/home/robert_sakana_ai/llm_cuda/experiments/20250203_optimize_b10_s4_e0_sweep/level_2/task_55/b3_s1_blocksize_tuning_opt/base/base.cu:43:20: warning: narrowing conversion from 'unsigned int' to signed type 'int' is implementation-defined [bugprone-narrowing-conversions]
43 | for (int seg = threadIdx.x; seg < pooled_len; seg += blockDim.x) {
| ^
/home/robert_sakana_ai/llm_cuda/experiments/20250203_optimize_b10_s4_e0_sweep/level_2/task_55/b3_s1_blocksize_tuning_opt/base/base.cu:43:58: warning: narrowing conversion from 'unsigned int' to signed type 'int' is implementation-defined [bugprone-narrowing-conversions]
43 | for (int seg = threadIdx.x; seg < pooled_len; seg += blockDim.x) {
| ^
/home/robert_sakana_ai/llm_cuda/experiments/20250203_optimize_b10_s4_e0_sweep/level_2/task_55/b3_s1_blocksize_tuning_opt/base/base.cu:60:16: warning: narrowing conversion from 'unsigned int' to signed type 'int' is implementation-defined [bugprone-narrowing-conversions]
60 | int lane = threadIdx.x & (warpSize - 1);
| ^
/home/robert_sakana_ai/llm_cuda/experiments/20250203_optimize_b10_s4_e0_sweep/level_2/task_55/b3_s1_blocksize_tuning_opt/base/base.cu:61:18: warning: narrowing conversion from 'unsigned int' to signed type 'int' is implementation-defined [bugprone-narrowing-conversions]
61 | int warpId = threadIdx.x / warpSize;
| ^
/home/robert_sakana_ai/llm_cuda/experiments/20250203_optimize_b10_s4_e0_sweep/level_2/task_55/b3_s1_blocksize_tuning_opt/base/base.cu:81:16: warning: the parameter 'x' is copied for each invocation but only used as a const reference; consider making it a const reference [performance-unnecessary-value-param]
81 | at::Tensor x,
| ^
| const &
/home/robert_sakana_ai/llm_cuda/experiments/20250203_optimize_b10_s4_e0_sweep/level_2/task_55/b3_s1_blocksize_tuning_opt/base/base.cu:84:16: warning: the parameter 'weight' is copied for each invocation but only used as a const reference; consider making it a const reference [performance-unnecessary-value-param]
84 | at::Tensor weight,
| ^
| const &
/home/robert_sakana_ai/llm_cuda/experiments/20250203_optimize_b10_s4_e0_sweep/level_2/task_55/b3_s1_blocksize_tuning_opt/base/base.cu:85:16: warning: the parameter 'bias' is copied for each invocation but only used as a const reference; consider making it a const reference [performance-unnecessary-value-param]
85 | at::Tensor bias
| ^
| const &
/home/robert_sakana_ai/llm_cuda/experiments/20250203_optimize_b10_s4_e0_sweep/level_2/task_55/b3_s1_blocksize_tuning_opt/base/base.cu:94:13: warning: narrowing conversion from 'int64_t' (aka 'long') to signed type 'int' is implementation-defined [bugprone-narrowing-conversions]
94 | int B = x.size(0);
| ^
/home/robert_sakana_ai/llm_cuda/experiments/20250203_optimize_b10_s4_e0_sweep/level_2/task_55/b3_s1_blocksize_tuning_opt/base/base.cu:95:15: warning: narrowing conversion from 'int64_t' (aka 'long') to signed type 'int' is implementation-defined [bugprone-narrowing-conversions]
95 | int inF = x.size(1);
| ^
/home/robert_sakana_ai/llm_cuda/experiments/20250203_optimize_b10_s4_e0_sweep/level_2/task_55/b3_s1_blocksize_tuning_opt/base/base.cu:96:16: warning: narrowing conversion from 'int64_t' (aka 'long') to signed type 'int' is implementation-defined [bugprone-narrowing-conversions]
96 | int outF = weight.size(0);
| ^