add 002-example

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broad-sea-life 2025-09-10 12:12:44 +08:00
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commit a4d4953fd3
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import torch
from torch.utils.cpp_extension import load_inline
# Swish激活函数的CUDA实现 (x * sigmoid(x))
swish_source = """
#include <torch/extension.h>
#include <cuda_runtime.h>
__global__ void swish_kernel(const float* x, float* y, int size) {
int idx = blockIdx.x * blockDim.x + threadIdx.x;
if (idx < size) {
// 高效计算Swish: x * (1 / (1 + exp(-x)))
float val = x[idx];
float sigmoid = 1.0f / (1.0f + expf(-val));
y[idx] = val * sigmoid;
}
}
torch::Tensor swish_cuda(torch::Tensor x) {
auto size = x.numel();
auto y = torch::empty_like(x);
const int block_size = 256;
int num_blocks = (size + block_size - 1) / block_size;
swish_kernel<<<num_blocks, block_size>>>(x.data_ptr<float>(), y.data_ptr<float>(), size);
return y;
}
"""
swish_cpp_source = """
torch::Tensor swish_cuda(torch::Tensor x);
"""
# 编译内联CUDA代码
swish = load_inline(
name="swish",
cpp_sources=swish_cpp_source,
cuda_sources=swish_source,
functions=["swish_cuda"],
verbose=True
)
class ModelNew(torch.nn.Module):
def __init__(self):
super(ModelNew, self).__init__()
self.swish = swish # 包含自定义Swish算子的模块
def forward(self, x):
return self.swish.swish_cuda(x)

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import torch
import torch.nn as nn
class Model(nn.Module):
def __init__(self):
super(Model, self).__init__()
def forward(self, x: torch.Tensor) -> torch.Tensor:
# 使用Swish替代原始的ReLU
return x * torch.sigmoid(x) # PyTorch内置Swish实现
batch_size = 16
dim = 16384
def get_inputs():
x = torch.randn(batch_size, dim)
return [x]
def get_init_inputs():
return [] # 不需要特殊初始化输入

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Write a custom CUDA kernel that fuses matrix multiplication with GELU activation.
The original architecture performs:
1. Matrix multiplication: output = input @ weight.T + bias
2. GELU activation: gelu_output = gelu(output)
You should fuse these two operations into a single CUDA kernel to avoid:
- Storing the intermediate matrix multiplication result to global memory
- Reading it back for the GELU operation
The GELU activation function can be approximated as:
gelu(x) = 0.5 * x * (1 + tanh(sqrt(2/π) * (x + 0.044715 * x^3)))
Considerations:
- Use 2D grid and block dimensions to parallelize over batch size and hidden features
- Implement efficient shared memory usage for tiling if possible
- Ensure numerical stability and precision
You are given the following architecture:
import torch
import torch.nn as nn
class Model(nn.Module):
def __init__(self, in_features=16384, hidden_features=4096):
super(Model, self).__init__()
self.linear = nn.Linear(in_features, hidden_features)
def forward(self, x):
x = self.linear(x)
return torch.nn.functional.gelu(x)

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import torch
import time
from example_torchcode import Model, get_inputs, get_init_inputs
from example_cudacode import ModelNew
def run_benchmark():
if not torch.cuda.is_available():
print("CUDA 不可用")
return
device = torch.device("cuda")
# 准备输入数据
inputs = [x.cuda(device=device) for x in get_inputs()]
init_inputs = [x.cuda(device=device) if isinstance(x, torch.Tensor) else x for x in get_init_inputs()]
# 初始化模型
torch_model = Model(*init_inputs).cuda()
cuda_model = ModelNew(*init_inputs).cuda()
torch_model.eval()
cuda_model.eval()
print("-------------------- 精度对齐验证 --------------------")
with torch.no_grad():
# 预热GPU
_ = torch_model(*inputs)
_ = cuda_model(*inputs)
# 正式测试
output_torch = torch_model(*inputs)
output_cuda = cuda_model(*inputs)
# 精度验证
abs_diff = torch.abs(output_torch - output_cuda)
max_diff = torch.max(abs_diff).item()
mean_diff = torch.mean(abs_diff).item()
if max_diff < 1e-4 and mean_diff < 1e-5:
print(f"✅ 精度对齐:最大误差 {max_diff:.6f},平均误差 {mean_diff:.6f}")
precision_flag = True
else:
print(f"❌ 精度不一致:最大误差 {max_diff:.6f},平均误差 {mean_diff:.6f}")
precision_flag = False
print("\n-------------------- 性能加速比测试 --------------------")
num_iterations = 100
# 预热GPU
for _ in range(10):
_ = torch_model(*inputs)
_ = cuda_model(*inputs)
# PyTorch模型计时
torch.cuda.synchronize()
start_time = time.time()
for _ in range(num_iterations):
_ = torch_model(*inputs)
torch.cuda.synchronize()
torch_time = (time.time() - start_time) / num_iterations
# 自定义CUDA内核计时
torch.cuda.synchronize()
start_time = time.time()
for _ in range(num_iterations):
_ = cuda_model(*inputs)
torch.cuda.synchronize()
cuda_time = (time.time() - start_time) / num_iterations
print(f"PyTorch内置Swish平均执行时间: {torch_time:.6f}")
print(f"自定义CUDA Swish平均执行时间: {cuda_time:.6f}")
speedup = torch_time / cuda_time if cuda_time > 0 else 0
print(f"加速比 (Speedup): {speedup:.2f}x")
return precision_flag, speedup
if __name__ == "__main__":
precision_flag, speedup = run_benchmark()