threads localized on the proper socket
This commit is courtesy of Intel (mikhail dot letavin at intel dot
com) who helped to optimize the code for the Xeon Phi.

A lot of prefetch (es) have been introduced.
if () {} else {} have been replaced by triadic operators whereever possible.
some int(s) have been moved to size_t for coherency (and efficiency).
Merging of kernels has been done to speedup the deltat computation.
A little more cleanup is done at code epilogue.