#include <stdio.h>
#include <time.h>
#include <x86intrin.h>


void matmul_avx(const float *x, const float **w,float *y,const int col,const int row){
    const int col_reduced_8 = col - col % 8;
    float scratchpad[8];
    __m256 op0, op1, tgt, tmp_vec;
    for (int i = 0; i < row; i++) {
        float res = 0;

        tgt = _mm256_setzero_ps();
        for (int j = 0; j < col_reduced_8; j += 8) {
            op0 = __builtin_ia32_loadups256(&x[j]);
            op1 = __builtin_ia32_loadups256(&w[i][j]);
            tmp_vec = __builtin_ia32_mulps256(op0, op1);
            tgt = __builtin_ia32_addps256(tmp_vec, tgt);
        }

        __builtin_ia32_storeups256(scratchpad, tgt);
        for (int k = 0; k < 8; k++)
            res += scratchpad[k];

        for (int l = col_reduced_8; l < col; l++) {
            res += w[i][l] * x[l];
        }
        y[i] = res;
    }
}

int main() {
    const int col = 2048, row = 512, num_mul = 10;

    float **w;
    float x[col];
    float y[row];
    float scratchpad[8];
    w = (float **)malloc(sizeof(float*)*row);
    for (int i = 0; i < row; i ++) { w[i] = (float *)malloc(sizeof(float) * col);	    }
    for (int i = 0; i < row; i++) {
        for (int j = 0; j < col; j++) {
            w[i][j] = (float) (rand() % 1000) / 800.0f;
        }
    }
    for (int j = 0; j < col; j++) {
        x[j] = (float) (rand() % 1000) / 800.0f;
    }

    clock_t t1, t2;
// The original matrix multiplication version
    t1 = clock();
    for (int r = 0; r < num_mul; r++)
        for (int j = 0; j < row; j++) {
            float sum = 0;
            float *wj = w[j];

            for (int i = 0; i < col; i++)
                sum += wj[i] * x[i];

            y[j] = sum;
        }
    t2 = clock();
    float diff = ((float) t2 - (float) t1) / (num_mul*CLOCKS_PER_SEC);
    printf("\nTime taken: %f second.\n", diff);

    for (int i = 0; i < row; i++) {
        printf("%.4f, ", y[i]);
        y[i]=0;
    }
    printf("\n");
// The avx matrix multiplication version.


    t1 = clock();
    for (int r = 0; r < num_mul; r++)
        matmul_avx(x,w,y,col,row);
    t2 = clock();
    diff = ((float) t2 - (float) t1) / (num_mul*CLOCKS_PER_SEC);
    printf("\nTime taken: %f second.\n",diff);

    for (int i = 0; i < row; i++) {
        printf("%.4f, ", y[i]);
    }
    printf("\n");
    
}
 

執行方式：

gcc -o test test.c -mavx

./test