Vectorize function calls

tempatel — Thu, 10 May 2012 16:15:02 GMT

I have an OpenCL program wich failed to vectorize. Problem is in function in line marked XXX

int getNumEigensLess(float c, int n, __global float *d, __global float *e, float pivmin) {

float diff = d[0] - c;

diff = select(diff, -pivmin, fabs(diff) < pivmin);

int count = select(0, 1, diff <= 0);

for (int j = 1; j < n; ++j) {

diff = d - c - sqr(e[j - 1]) / diff; // XXX here is a problem line

diff = select(diff, -pivmin, fabs(diff) < pivmin);

count += select(0, 1, diff <= 0);

}

return count;

}

I see, that vectorization fails because each successive diff value depends on previous. But there is an another way. As far as I know, all non kernel functions are inlined in OpenCL, so instead of vectorizationgetNumEigensLess itself, compiler can vectorize function calls. Make signature something like

int4 getNumEigensLess(float4 c, int n, __global float *d, __global float *e, float pivmin)

Obviously I use same n, e, d and pivmin parameters between calls, changing only c.

How can I change my code, to make compiler vectorize function calls like this?

Vectorize function calls

tempatel — Thu, 10 May 2012 16:22:16 GMT

Substituting function body instead of a call has no effect either

sujet Vectorize function calls dans OpenCL* for CPU

Vectorize function calls

Vectorize function calls