<html><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; "><br><div><div>On Dec 1, 2009, at 7:14 , amjad ali wrote:</div><blockquote type="cite"><span class="Apple-style-span" style="border-collapse: separate; color: rgb(0, 0, 0); font-family: Helvetica; font-size: medium; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: 2; text-align: auto; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-border-horizontal-spacing: 0px; -webkit-border-vertical-spacing: 0px; -webkit-text-decorations-in-effect: none; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; "><div><div style="margin-top: 0in; margin-right: 0in; margin-bottom: 0.0001pt; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman'; ">My question is that if we do not have free cpu cores in a PC or cluster (all cores are running MPI processes), still the auto-vertorization is beneficial? Or it is beneficial only if we have some free cpu cores locally?<span class="Apple-converted-space"> </span><br></div></div></span></blockquote></div><div apple-content-edited="true"><br class="Apple-interchange-newline"> </div><div apple-content-edited="true"><br></div>Amjad,<div><br></div><div>Vectorization is in x86_64 parlor a compilation technique where the compiler will utilize certain instructions which operate on short vectors. When you execute such a program on a particular core, these vector-instructions will execute on special execution unit _within_ the core you're executing on. Hence, no additional resources or cores are required to use vector instructions and you will benefit from them independent of whether you fully use all cores in your cluster or not.</div><div><br></div><div>Håkon</div></body></html>