[llvm-dev] Vectorization width not correct using #pragma clang loop vectorize_width

[hameeza ahmed via llvm-dev]

Hello,
I m trying to set vector width using #pragma clang loop vectorize_width(32)
but i m getting width 8 for the following kernel;

#define M 128
#define N 128

#define SQRT_FUN(x) sqrtf(x)
int main(int argc, char** argv)
{
    /* Variable declaration/allocation. */
    double float_n = (double)N;
    double data[N*M];
    double corr[M*M];
    double mean[M];
    double stddev[M];
    uint32_t i,j,k;

    /*Initialize array(s). */
   #pragma clang loop vectorize_width(1) //no vectorize
    for (i = 0; i < N*M; i++)
    {
        data[i] = (50.0)*i;
    }
kernel_1:
    #pragma clang loop vectorize_width(32)
    for (j = 0; j < M; j++)
    {
        mean[j] = 0.0;
    }
    for (i = 0; i < N; i++)
    {
        for (j = 0; j < M; j++)
            mean[j] += data[(i*M) + j];
    }
    for (j = 0; j < M; j++)
    {
        mean[j] /= float_n;
    }
kernel_2:
    for (j = 0; j < M; j++)
    {
        stddev[j] = 0.0;
    }
    for (i = 0; i < N; i++)
    {
        for (j = 0; j < M; j++)
        {
            stddev[j] += (data[(i*M) + j] - mean[j]) * (data[(i*M)+j] -
mean[j]);
        }
    }
    for (j = 0; j < M; j++)
    {
        stddev[j] /= float_n;
    }
    for (j = 0; j < M; j++)
    {
        stddev[j] = SQRT_FUN(stddev[j]);
    }
kernel_3:
    for (i = 0; i < N; i++)
    {
        for (j = 0; j < M; j++)
        {
            data[(i*M) + j] -= mean[j];
        }
    }
    for (i = 0; i < N; i++)
    {
        for (j = 0; j < M; j++)
        {
            data[(i*M) + j] /= SQRT_FUN(float_n) * stddev[j];
        }
    }
kernel_4:

    for (i = 0; i < M*M; i++)
    {
        corr[i] = 0.0;
    }
    for (k = 0; k < N; k++)
    {
        for (i = 0; i < M-1; i++)
        {
            for (j = i+1; j < M; j++)
            {
                corr[(i*M)+j] += (data[(k*M)+i] *
data[(k*M)+j]);
            }
        }
    }
    printf("Corr[0]: %lf\n",mean[0]);
    printf("Corr[0]: %lf\n",mean[M-1]);
    printf("Corr[0]: %lf\n",stddev[0]);
    printf("Corr[0]: %lf\n",stddev[M-1]);
    printf("Corr[0]: %lf\n",corr[0]);
    printf("Corr[(M*M)-1]: %lf\n",corr[(M*M)-1]);
    printf("Corr[0]: %lf\n",data[0]);
    printf("Corr[(M*M)-1]: %lf\n",data[(M*M)-1]);
    return 0;
}
*i m getting following output when i compiled;*






















*clang -O3  correlation.c   -Rpass=loop-vectorize  -emit-llvm -march=knl
-S  -o 1.llcorrelation.c:38:9: remark: vectorized loop (vectorization
width: 8, interleaved count: 4) [-Rpass=loop-vectorize]        for (j = 0;
j < M; j++)        ^correlation.c:41:5: remark: vectorized loop
(vectorization width: 8, interleaved count: 4) [-Rpass=loop-vectorize]
for (j = 0; j < M; j++)    ^correlation.c:53:9: remark: vectorized loop
(vectorization width: 8, interleaved count: 4)
[-Rpass=loop-vectorize]        for (j = 0; j < M; j++)
^correlation.c:58:5: remark: vectorized loop (vectorization width: 8,
interleaved count: 4) [-Rpass=loop-vectorize]    for (j = 0; j < M; j++)
^correlation.c:71:9: remark: vectorized loop (vectorization width: 8,
interleaved count: 4) [-Rpass=loop-vectorize]        for (j = 0; j < M;
j++)        ^correlation.c:78:9: remark: vectorized loop (vectorization
width: 8, interleaved count: 4) [-Rpass=loop-vectorize]        for (j = 0;
j < M; j++)        ^correlation.c:98:13: remark: vectorized loop
(vectorization width: 8, interleaved count: 4)
[-Rpass=loop-vectorize]            for (j = i+1; j < M; j++)*

*why is that so?*

*although i m able to set width to 32 of the example code given on site.*

*Why Pragmas are not setting vector width correctly here in my kernel?*

*What is the issue?*

*Please help..*

*Thank You*
*Regards*
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