Merge pull request 'feat add a selu_clip1 #4' (#196) from zizi05/GPUCodeForces:selu_clip1 into main

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Kuohais 2025-11-27 15:41:50 +08:00
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You write custom CUDA kernels to replace the PyTorch operators in the given SELU-Clip activation architecture to get speedups.
You have complete freedom to choose the set of operators you want to replace. You may make the decision to replace the combined SELU calculation and clamp operators with a custom CUDA kernel (considering operator fusion opportunities to combine the element-wise SELU computation and range clipping into a single kernel) or adjust algorithms for better performance. You are only limited by your imagination.
Here's an example to show you the syntax of inline embedding custom CUDA operators in PyTorch (for reference of code structure, not functional alignment):
The example given architecture (sample structure):
import torch
import torch.nn as nn
import torch.nn.functional as F
class Model(nn.Module):
def __init__(self) -> None:
super().__init__()
def forward(self, a, b):
return a + b
def get_inputs():
# randomly generate input tensors based on the model architecture
a = torch.randn(1, 128).cuda()
b = torch.randn(1, 128).cuda()
return [a, b]
def get_init_inputs():
# randomly generate tensors required for initialization based on the model architecture
return []
The example new arch with custom CUDA kernels (sample structure):
import torch
import torch.nn as nn
import torch.nn.functional as F
from torch.utils.cpp_extension import load_inline
# Define custom CUDA kernel and load it inline
custom_add_source = """
#include <torch/extension.h>
#include <cuda_runtime.h>
__global__ void custom_add_kernel(const float* a, const float* b, float* out, int size) {
int idx = blockIdx.x * blockDim.x + threadIdx.x;
if (idx < size) {
out[idx] = a[idx] + b[idx];
}
}
torch::Tensor custom_add_cuda(torch::Tensor a, torch::Tensor b) {
auto size = a.numel();
auto out = torch::empty_like(a);
const int block_size = 256;
int num_blocks = (size + block_size - 1) / block_size;
custom_add_kernel<<<num_blocks, block_size>>>(a.data_ptr<float>(), b.data_ptr<float>(), out.data_ptr<float>(), size);
return out;
}
"""
custom_add_cpp_source = "torch::Tensor custom_add_cuda(torch::Tensor a, torch::Tensor b);"
custom_add = load_inline(
name="custom_add",
cpp_sources=custom_add_cpp_source,
cuda_sources=custom_add_source,
functions=["custom_add_cuda"],
verbose=True
)
class Model(nn.Module):
def __init__(self) -> None:
super().__init__()
self.custom_add = custom_add
def forward(self, a, b):
return self.custom_add.custom_add_cuda(a, b)
def get_inputs():
# randomly generate input tensors based on the model architecture
a = torch.randn(1, 128).cuda()
b = torch.randn(1, 128).cuda()
return [a, b]
def get_init_inputs():
# randomly generate tensors required for initialization based on the model architecture
return []
You are given the following SELU-Clip activation architecture (base PyTorch implementation):
import torch
import torch.nn as nn
class Model(nn.Module):
"""
SELU-Clip activation function: Mathematical formulation is clamp(scale * (x if x > 0 else alpha*(exp(x)-1)), clip_min, clip_max),
where alpha=1.6732632423543772 (SELU shape parameter), scale=1.0507009873554804 (SELU scaling parameter),
clip_min=-5.0 (minimum clipping value), clip_max=5.0 (maximum clipping value).
"""
def __init__(self, alpha=1.6732632423543772, scale=1.0507009873554804, clip_min=-5.0, clip_max=5.0):
super(Model, self).__init__()
self.alpha = alpha
self.scale = scale
self.clip_min = clip_min
self.clip_max = clip_max
def forward(self, x: torch.Tensor) -> torch.Tensor:
"""
Applies SELU-Clip activation to the input tensor.
Args:
x (torch.Tensor): Input tensor with fixed shape (batch_size, dim)
where batch_size=1024 and dim=2048.
Returns:
torch.Tensor: Output tensor with SELU-Clip applied, same shape as input.
"""
# Calculate SELU
selu_out = self.scale * torch.where(
x > 0,
x,
self.alpha * (torch.exp(x) - 1)
)
# Apply clipping
clipped_out = torch.clamp(selu_out, self.clip_min, self.clip_max)
return clipped_out
batch_size = 1024
dim = 2048
def get_inputs():
# Randomly generate input tensor matching the fixed shape (batch_size, dim)
x = torch.randn(batch_size, dim)
return [x]
def get_init_inputs():
# Provide initialization parameters for the model (non-trainable hyperparameters)
return (1.6732632423543772, 1.0507009873554804, -5.0, 5.0)

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###########################################################
# 性能和精度验证程序
###########################################################
import torch
import torch.nn as nn
import time
from selu_clip_torchcode import Model,get_inputs,get_init_inputs
from selu_clip_cudacode import ModelNew
def run_benchmark():
# 检查 CUDA 是否可用
if not torch.cuda.is_available():
print("CUDA 不可用,请确保您有可用的 NVIDIA GPU 并已正确安装 PyTorch CUDA 版本。")
return
else:
device = torch.device("cuda")
# 初始化模型
init_inputs = get_init_inputs()
init_inputs = [
x.cuda(device=device) if isinstance(x, torch.Tensor) else x for x in init_inputs
]
inputs = get_inputs()
inputs = [
x.cuda(device=device) if isinstance(x, torch.Tensor) else x for x in inputs
]
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():
output_torch = torch_model( *inputs)
output_cuda = cuda_model(*inputs)
precision_flag = torch.allclose(output_torch, output_cuda,rtol=1e-03)
if precision_flag:
print("✅ 精度对齐:两个模型的输出结果非常接近。")
else:
print("❌ 精度不一致!")
print("\n-------------------- 性能加速比测试 --------------------")
num_iterations = 100
# 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 selu_clip 平均执行时间: {torch_time:.6f}")
print(f"自定义 CUDA 内核 平均执行时间: {cuda_time:.6f}")
speedup = 0
if cuda_time > 0:
speedup = torch_time / cuda_time
print(f"加速比 (Speedup): {speedup:.2f}x")
else:
print("CUDA 内核执行时间为0无法计算加速比。")
return precision_flag,speedup
if __name__ == "__main__":
precision_flag,speedup = run_benchmark()

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import torch
import torch.nn as nn
from torch.autograd import Function
from torch.utils.cpp_extension import load_inline
# 定义CUDA内核和C++绑定代码
cuda_source = """
#include <torch/extension.h>
#include <cuda.h>
#include <cuda_runtime.h>
#include <vector>
// SELU-Clip前向传播CUDA内核
__global__ void selu_clip_forward_kernel(
const float* __restrict__ x,
float* __restrict__ output,
float alpha,
float scale,
float clip_min,
float clip_max,
int num_elements) {
int idx = blockIdx.x * blockDim.x + threadIdx.x;
if (idx < num_elements) {
float val = x[idx];
// 计算SELU
float selu_val;
if (val > 0.0f) {
selu_val = scale * val;
} else {
selu_val = scale * alpha * (expf(val) - 1.0f);
}
// 裁剪操作
if (selu_val < clip_min) {
output[idx] = clip_min;
} else if (selu_val > clip_max) {
output[idx] = clip_max;
} else {
output[idx] = selu_val;
}
}
}
// SELU-Clip反向传播CUDA内核
__global__ void selu_clip_backward_kernel(
const float* __restrict__ x,
const float* __restrict__ grad_output,
float* __restrict__ grad_input,
float alpha,
float scale,
int num_elements) {
int idx = blockIdx.x * blockDim.x + threadIdx.x;
if (idx < num_elements) {
float val = x[idx];
float grad = grad_output[idx];
// 计算梯度
if (val > 0.0f) {
grad_input[idx] = scale * grad;
} else {
grad_input[idx] = scale * alpha * expf(val) * grad;
}
}
}
// C++绑定前向函数
torch::Tensor selu_clip_forward(
torch::Tensor x,
float alpha,
float scale,
float clip_min,
float clip_max) {
auto output = torch::empty_like(x);
int num_elements = x.numel();
int block_size = 256;
int grid_size = (num_elements + block_size - 1) / block_size;
selu_clip_forward_kernel<<<grid_size, block_size>>>(
x.data_ptr<float>(),
output.data_ptr<float>(),
alpha,
scale,
clip_min,
clip_max,
num_elements
);
return output;
}
// C++绑定反向函数
torch::Tensor selu_clip_backward(
torch::Tensor x,
torch::Tensor grad_output,
float alpha,
float scale) {
auto grad_input = torch::empty_like(x);
int num_elements = x.numel();
int block_size = 256;
int grid_size = (num_elements + block_size - 1) / block_size;
selu_clip_backward_kernel<<<grid_size, block_size>>>(
x.data_ptr<float>(),
grad_output.data_ptr<float>(),
grad_input.data_ptr<float>(),
alpha,
scale,
num_elements
);
return grad_input;
}
PYBIND11_MODULE(TORCH_EXTENSION_NAME, m) {
m.def("forward", &selu_clip_forward, "SELU-Clip forward");
m.def("backward", &selu_clip_backward, "SELU-Clip backward");
}
"""
# 动态编译CUDA内核
selu_clip_cuda = load_inline(
name="selu_clip_cuda",
cpp_sources=[],
cuda_sources=[cuda_source],
extra_cuda_cflags=["-O2"],
with_cuda=True,
verbose=False
)
class SELUClipFunction(Function):
"""自定义CUDA实现的SELU-Clip算子函数"""
@staticmethod
def forward(ctx, x, alpha, scale, clip_min, clip_max):
ctx.alpha = alpha
ctx.scale = scale
ctx.save_for_backward(x)
return selu_clip_cuda.forward(x, alpha, scale, clip_min, clip_max)
@staticmethod
def backward(ctx, grad_output):
x, = ctx.saved_tensors
alpha = ctx.alpha
scale = ctx.scale
grad_input = selu_clip_cuda.backward(x, grad_output, alpha, scale)
return grad_input, None, None, None, None
class ModelNew(nn.Module):
"""使用内置CUDA内核的SELU-Clip模型"""
def __init__(self, alpha=1.6732632423543772, scale=1.0507009873554804, clip_min=-5.0, clip_max=5.0):
super(ModelNew, self).__init__()
self.alpha = alpha
self.scale = scale
self.clip_min = clip_min
self.clip_max = clip_max
def forward(self, x):
return SELUClipFunction.apply(x, self.alpha, self.scale, self.clip_min, self.clip_max)

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import torch
import torch.nn as nn
class Model(nn.Module):
"""PyTorch实现的SELU-Clip算子"""
def __init__(self, alpha=1.6732632423543772, scale=1.0507009873554804, clip_min=-5.0, clip_max=5.0):
super(Model, self).__init__()
self.alpha = alpha
self.scale = scale
self.clip_min = clip_min
self.clip_max = clip_max
def forward(self, x):
# 计算SELU
selu_out = self.scale * torch.where(
x > 0,
x,
self.alpha * (torch.exp(x) - 1)
)
# 裁剪操作
clipped_out = torch.clamp(selu_out, self.clip_min, self.clip_max)
return clipped_out
def get_init_inputs():
"""提供模型初始化参数"""
return (1.6732632423543772, 1.0507009873554804, -5.0, 5.0)
def get_inputs():
"""提供测试输入数据"""
torch.manual_seed(42)
x = torch.randn(1024, 2048) # 典型特征张量形状
return (x,)