AVX SSE 性能實驗
代碼
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#include “math_function.h”
float MathMulAdd(const float *input1, const float *input2, int size)
{
float output = 0.0;
for (int i = 0; i < size; i++)
{
output += input1[i] * input2[i];
}
return output;
}
float SSEMulAdd(const float *input1, const float *input2, int size)
{
if (input1 == nullptr || input2 == nullptr)
{
printf(“input data is null\n”);
return -1;
}
int nBlockWidth = 4;
int cntBlock = size / nBlockWidth;
int cntRem = size % nBlockWidth;
float output = 0;
__m128 loadData1, loadData2;
__m128 mulData = _mm_setzero_ps();
__m128 sumData = _mm_setzero_ps();
const float *p1 = input1;
const float *p2 = input2;
for (int i = 0; i < cntBlock; i++)
{
loadData1 = _mm_load_ps(p1);
loadData2 = _mm_load_ps(p2);
mulData = _mm_mul_ps(loadData1, loadData2);
sumData = _mm_add_ps(sumData, mulData);
p1 += nBlockWidth;
p2 += nBlockWidth;
}
sumData = _mm_hadd_ps(sumData, sumData); // p[0] + p[1] + p[4] + p[5] + ...
sumData = _mm_hadd_ps(sumData, sumData); // p[2] + p[3] + p[6] + p[7] + ...
//output += sumData.m128_f32[(0)]; // 前4組 Windows下這樣處理是一個聯合體
const float *q;
q = (const float *)&sumData;
output += q[0];
//數組長度16位元組對齊（這部分是非對其
for (int i = 0; i < cntRem; i++)
{
output += p1[i] * p2[i];
}
return output;
}
float SSEFmAdd(const float *input1, const float *input2, int size)
{
if (input1 == nullptr || input2 == nullptr)
{
printf(“input data is null\n”);
return -1;
}
int nBlockWidth = 4;
int cntBlock = size / nBlockWidth;
int cntRem = size % nBlockWidth;
float output = 0;
__m128 loadData1, loadData2;
//__m128 mulData = _mm_setzero_ps();
__m128 sumData = _mm_setzero_ps();
const float *p1 = input1;
const float *p2 = input2;
for (int i = 0; i < cntBlock; i++)
{
loadData1 = _mm_load_ps(p1);
loadData2 = _mm_load_ps(p2);
//mulData = _mm_mul_ps(loadData1, loadData2);
//sumData = _mm_add_ps(sumData, mulData);
sumData = _mm_fmadd_ps(loadData1, loadData2, sumData);
p1 += nBlockWidth;
p2 += nBlockWidth;
}
sumData = _mm_hadd_ps(sumData, sumData); // p[0] + p[1] + p[4] + p[5] + ...
sumData = _mm_hadd_ps(sumData, sumData); // p[2] + p[3] + p[6] + p[7] + ...
//output += sumData.m128_f32[(0)]; // 前4組
const float *q;
q = (const float *)&sumData;
output += q[0];
for (int i = 0; i < cntRem; i++)
{
output += p1[i] * p2[i];
}
return output;
}
float AVXMulAdd(const float *input1, const float *input2, int size)
{
if (input1 == nullptr || input2 == nullptr)
{
printf(“input data is null\n”);
return -1;
}
int nBlockWidth = 8;
int cntBlock = size / nBlockWidth;
int cntRem = size % nBlockWidth;
float output = 0;
__m256 loadData1, loadData2;
__m256 mulData = _mm256_setzero_ps();
__m256 sumData = _mm256_setzero_ps();
const float *p1 = input1;
const float *p2 = input2;
for (int i = 0; i < cntBlock; i++)
{
loadData1 = _mm256_loadu_ps(p1);
loadData2 = _mm256_loadu_ps(p2);
mulData = _mm256_mul_ps(loadData1, loadData2);
sumData = _mm256_add_ps(sumData, mulData);
p1 += nBlockWidth;
p2 += nBlockWidth;
}
sumData = _mm256_hadd_ps(sumData, sumData); // p[0] + p[1] + p[4] + p[5] + p[8] + p[9] + p[12] + p[13] + ...
sumData = _mm256_hadd_ps(sumData, sumData); // p[2] + p[3] + p[6] + p[7] + p[10] + p[11] + p[14] + p[15] + ...
const float *q;
q = (const float *)&sumData;
//output += q[0];
output += q[0]; // 前4組
output += q[4]; // 後4組
for (int i = 0; i < cntRem; i++)
{
output += p1[i] * p2[i];
}
return output;
}
float AVXFmAdd(const float *input1, const float *input2, int size)
{
if (input1 == nullptr || input2 == nullptr)
{
printf(“input data is null\n”);
return -1;
}
int nBlockWidth = 8;
int cntBlock = size / nBlockWidth;
int cntRem = size % nBlockWidth;
float output = 0;
__m256 loadData1, loadData2;
//__m256 mulData = _mm256_setzero_ps();
__m256 sumData = _mm256_setzero_ps();
const float *p1 = input1;
const float *p2 = input2;
for (int i = 0; i < cntBlock; i++)
{
loadData1 = _mm256_loadu_ps(p1);
loadData2 = _mm256_loadu_ps(p2);
//mulData = _mm256_mul_ps(loadData1, loadData2);
//sumData = _mm256_add_ps(sumData, mulData);
sumData = _mm256_fmadd_ps(loadData1, loadData2, sumData);
p1 += nBlockWidth;
p2 += nBlockWidth;
}
sumData = _mm256_hadd_ps(sumData, sumData); // p[0] + p[1] + p[4] + p[5] + p[8] + p[9] + p[12] + p[13] + ...
sumData = _mm256_hadd_ps(sumData, sumData); // p[2] + p[3] + p[6] + p[7] + p[10] + p[11] + p[14] + p[15] + ...
const float *q;
q = (const float *)&sumData;
//output += q[0];
output += q[0]; // 前4組
output += q[4]; // 後4組
for (int i = 0; i < cntRem; i++)
{
output += p1[i] * p2[i];
}
return output;
}
···
main.cpp測試代碼
#include "math_function.h"
#include <random>
#include <time.h>
using std::default_random_engine;
using std::uniform_real_distribution;
int main(int argc, char* argv[])
{
int size = 325400;
int align_size = 32;
float *x1 = (float *)malloc(sizeof(float) * (align_size + size)) ;
float *x2 = (float *)malloc(sizeof(float) * (align_size + size)) ;
float *input1 = (float *)((((unsigned long)x1) + 127)/align_size*align_size);
float *input2 = (float *)((((unsigned long)x2) + 127)/align_size*align_size);
default_random_engine e;
uniform_real_distribution<float> u(0, 1); //随機數分布對象
for (int i = 0; i < size; i++)
{
input1[i] = u(e);
input2[i] = u(e);
}
int cntLoop = 1;
clock_t start_t = clock();
float org = 0.0;
for (int i = 0; i < cntLoop; i++)
org = MathMulAdd(input1, input2, size);
clock_t end_t = clock();
printf("org = %f\t", org);
printf("cost time: %d(ms)\n", end_t - start_t);
start_t = clock();
float sse = 0.0;
for (int i = 0; i < cntLoop; i++)
sse = SSEMulAdd(input1, input2, size);
end_t = clock();
printf("sse = %f\t", sse);
printf("cost time: %d(ms)\n", end_t - start_t);
start_t = clock();
float sse_ = 0.0;
for (int i = 0; i < cntLoop; i++)
sse_ = SSEFmAdd(input1, input2, size);
end_t = clock();
printf("sse_= %f\t", sse_);
printf("cost time: %d(ms)\n", end_t - start_t);
start_t = clock();
float avx = 0.0;
for (int i = 0; i < cntLoop; i++)
avx = AVXMulAdd(input1, input2, size);
end_t = clock();
printf("avx = %f\t", avx);
printf("cost time: %d(ms)\n", end_t - start_t);
start_t = clock();
float avx_ = 0.0;
for (int i = 0; i < cntLoop; i++)
avx_ = AVXFmAdd(input1, input2, size);
end_t = clock();
printf("avx_= %f\t", avx_);
printf("cost time: %d(ms)\n", end_t - start_t);
//getchar();
free(x1);
free(x2);
return 0;
}
編譯
g++ -O3 -mavx -march=native -m64 -Wall -std=c++11 main.cpp math_function.cpp math_function.h -o cpu_opt
測試結果
- avx load對齊
AVX SSE 性能實驗AVX SSE 性能實驗 - avx load不對齊
AVX SSE 性能實驗AVX SSE 性能實驗
結論
- 128 sse 速度差不多達到了普通算法的4倍 （理論值是4倍）
- 256 avx 速度達到了普通算法的7倍多（理論值是8倍）
- 對于avx而言對不對齊速度上差距不大