Newsgroups: comp.parallel.mpi
From: salo@cray.com (Eric Salo)
Subject: Re: Cost of MPI_Wtime
Organization: Silicon Graphics, Inc.
Date: 6 Aug 1997 15:25:05 GMT
Message-ID: <5sa50h$n7$1@walter.cray.com>

>Does anyone know how expensive the call to MPI_Wtime on 
>an SGI Origin 2K is?  This is with Array 3.0.

It's very cheap. There's the normal function call overhead, of course,
followed by a single uncached read of a hardware counter and a single
floating-point multiply.

If you're asking for a real number, I don't have one, but on Power Challenge
I believe it was less than 2 usecs. One would hope (knock on wood) that
Origin would be faster...
--
Eric Salo      Silicon Graphics      salo@sgi.com