Re: [Beowulf] Peformance penalty when using 128-bit reals on AMD64

2010-06-26 Thread Greg Lindahl
On Sat, Jun 26, 2010 at 03:40:24PM -0700, NiftyOMPI Tom Mitchell wrote: > In a 30 second scan of GMP's arbitrary precision library I cannot tell > if 32 and 64bit sizes fall out as equal in performance to native types. No. It's great for arbitrary large sizes and not so good for 128 bits, compare

Re: [Beowulf] Peformance penalty when using 128-bit reals on AMD64

2010-06-26 Thread NiftyOMPI Tom Mitchell
On Fri, Jun 25, 2010 at 10:30 AM, Nathan Moore wrote: ...snip... > I used GMP's arbitrary precision library (rational number arithmetic) > for my thesis a few years back.  It was very easy to implement, but > not fast (better on x86 hardware than sun/sgi/power as I recall).  I > too am curious abo

[Beowulf] MPI Persistent Comm Question

2010-06-26 Thread amjad ali
Hi all, What is the be the best way of using MPI persistent communication in an iterative/repetative kind of code about calling MPI_Free(); Should we call MPI_Free() in every iteration or only once when all the iterations/repetitions are performed? Means which one is the best out of following two:

Re: [Beowulf] Peformance penalty when using 128-bit reals on AMD64

2010-06-26 Thread Derek R.
Prentice, As was said before, I don't believe that x64 processor architectures support 128 bit precision instructions either (I did glance through the official AMD manuals, and I've read the first 3 in the set for another project, and I can't recall anything about operating on variables that large;