forked from ccf-ai-infra/GPUCodeForces
add 002-example
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import torch
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from torch.utils.cpp_extension import load_inline
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# Swish激活函数的CUDA实现 (x * sigmoid(x))
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swish_source = """
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#include <torch/extension.h>
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#include <cuda_runtime.h>
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__global__ void swish_kernel(const float* x, float* y, int size) {
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int idx = blockIdx.x * blockDim.x + threadIdx.x;
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if (idx < size) {
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// 高效计算Swish: x * (1 / (1 + exp(-x)))
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float val = x[idx];
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float sigmoid = 1.0f / (1.0f + expf(-val));
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y[idx] = val * sigmoid;
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}
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}
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torch::Tensor swish_cuda(torch::Tensor x) {
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auto size = x.numel();
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auto y = torch::empty_like(x);
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const int block_size = 256;
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int num_blocks = (size + block_size - 1) / block_size;
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swish_kernel<<<num_blocks, block_size>>>(x.data_ptr<float>(), y.data_ptr<float>(), size);
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return y;
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}
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"""
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swish_cpp_source = """
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torch::Tensor swish_cuda(torch::Tensor x);
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"""
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# 编译内联CUDA代码
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swish = load_inline(
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name="swish",
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cpp_sources=swish_cpp_source,
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cuda_sources=swish_source,
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functions=["swish_cuda"],
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verbose=True
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)
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class ModelNew(torch.nn.Module):
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def __init__(self):
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super(ModelNew, self).__init__()
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self.swish = swish # 包含自定义Swish算子的模块
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def forward(self, x):
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return self.swish.swish_cuda(x)
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import torch
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import torch.nn as nn
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class Model(nn.Module):
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def __init__(self):
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super(Model, self).__init__()
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def forward(self, x: torch.Tensor) -> torch.Tensor:
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# 使用Swish替代原始的ReLU
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return x * torch.sigmoid(x) # PyTorch内置Swish实现
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batch_size = 16
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dim = 16384
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def get_inputs():
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x = torch.randn(batch_size, dim)
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return [x]
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def get_init_inputs():
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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.
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The original architecture performs:
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1. Matrix multiplication: output = input @ weight.T + bias
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2. GELU activation: gelu_output = gelu(output)
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You should fuse these two operations into a single CUDA kernel to avoid:
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- Storing the intermediate matrix multiplication result to global memory
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- Reading it back for the GELU operation
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The GELU activation function can be approximated as:
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gelu(x) = 0.5 * x * (1 + tanh(sqrt(2/π) * (x + 0.044715 * x^3)))
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Considerations:
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- Use 2D grid and block dimensions to parallelize over batch size and hidden features
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- Implement efficient shared memory usage for tiling if possible
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- Ensure numerical stability and precision
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You are given the following architecture:
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import torch
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import torch.nn as nn
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class Model(nn.Module):
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def __init__(self, in_features=16384, hidden_features=4096):
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super(Model, self).__init__()
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self.linear = nn.Linear(in_features, hidden_features)
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def forward(self, x):
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x = self.linear(x)
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return torch.nn.functional.gelu(x)
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import torch
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import time
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from example_torchcode import Model, get_inputs, get_init_inputs
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from example_cudacode import ModelNew
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def run_benchmark():
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if not torch.cuda.is_available():
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print("CUDA 不可用")
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return
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device = torch.device("cuda")
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# 准备输入数据
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inputs = [x.cuda(device=device) for x in get_inputs()]
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init_inputs = [x.cuda(device=device) if isinstance(x, torch.Tensor) else x for x in get_init_inputs()]
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# 初始化模型
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torch_model = Model(*init_inputs).cuda()
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cuda_model = ModelNew(*init_inputs).cuda()
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torch_model.eval()
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cuda_model.eval()
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print("-------------------- 精度对齐验证 --------------------")
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with torch.no_grad():
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# 预热GPU
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_ = torch_model(*inputs)
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_ = cuda_model(*inputs)
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# 正式测试
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output_torch = torch_model(*inputs)
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output_cuda = cuda_model(*inputs)
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# 精度验证
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abs_diff = torch.abs(output_torch - output_cuda)
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max_diff = torch.max(abs_diff).item()
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mean_diff = torch.mean(abs_diff).item()
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if max_diff < 1e-4 and mean_diff < 1e-5:
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print(f"✅ 精度对齐:最大误差 {max_diff:.6f},平均误差 {mean_diff:.6f}")
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precision_flag = True
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else:
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print(f"❌ 精度不一致:最大误差 {max_diff:.6f},平均误差 {mean_diff:.6f}")
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precision_flag = False
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print("\n-------------------- 性能加速比测试 --------------------")
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num_iterations = 100
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# 预热GPU
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for _ in range(10):
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_ = torch_model(*inputs)
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_ = cuda_model(*inputs)
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# PyTorch模型计时
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torch.cuda.synchronize()
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start_time = time.time()
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for _ in range(num_iterations):
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_ = torch_model(*inputs)
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torch.cuda.synchronize()
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torch_time = (time.time() - start_time) / num_iterations
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# 自定义CUDA内核计时
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torch.cuda.synchronize()
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start_time = time.time()
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for _ in range(num_iterations):
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_ = cuda_model(*inputs)
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torch.cuda.synchronize()
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cuda_time = (time.time() - start_time) / num_iterations
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print(f"PyTorch内置Swish平均执行时间: {torch_time:.6f}秒")
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print(f"自定义CUDA Swish平均执行时间: {cuda_time:.6f}秒")
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speedup = torch_time / cuda_time if cuda_time > 0 else 0
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print(f"加速比 (Speedup): {speedup:.2f}x")
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return precision_flag, speedup
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if __name__ == "__main__":
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precision_flag, speedup = run_benchmark()
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