- One more feature you can use is logical operations and masks:
for example instead of:
// process only 1
if (p > 0)
p = p*(p-1)/2 + fRadius*p;
you can write
// processes 4 floats
const __m128 &mask = _mm_cmplt_ps(p,0);
const __m128 ¬Mask = _mm_cmplt_ps(0,p);
const __m128 &p_tmp = ( p*(p-1)/2 + fRadius*p );
p = _mm_add_ps(_mm_and_ps(p_tmp, mask), _mm_and_ps(p, notMask)); // = p_tmp & mask + p & !mask
Also I can recommend you to use a special libraries, which overloads instructions. For example: http://code.compeng.uni-frankfurt.de/projects/vc
dif
variable makes iterations of inner loop dependent. You should try to parallelize the outer loop. But with out instructions overloading the code will become unmanageable then.Also consider rethinking the whole algorithm. Current one doesn't look paralell. May be you can neglect precision, or increase scalar time a bit?