[molpro-user] infiniband latency

[Manhui Wang]

Dear Benjamin,

I think it is related to the way by which latency/bandwidth is
determined. Latency number in Molpro is determined as the time spent on
broadcasting 1024 double precision numbers (ie, 1024*8 bytes), while
reported latency number in HPC Performance Test might be determined by
MPI ping-pong test(send/receive a small number of data, eg, 1,4,or 8
bytes etc). As for bandwidth, Molpro reports the broadcast speed, while
HPC Performance Test might use MPI standard send and receive routines to
 get the bandwidth number.

Best wishes,
Manhui

Mintz, Benjamin J. wrote:
> Dear users,
> 
> I recently built a mpp version of molpro 2010.1, and I had a question about the result from mpptune.com.  Our cluster is set up with dual quad-core intel nehalem processors, and we have an infiniband interconnect using openmpi, openib, and SGE.  I ran the mpptune.com, which put the following lines in lib/tuning.rc
> 
> --tuning-mpplat 000035
> --tuning-mppspeed 000249
> 
> I believe this means that molpro determined that our network has a latency of 35 microseconds and a broadcast speed of 249 MB/sec.  My question is wether or not this is a good latency and broadcast speed for an infiniband interconnect running molpro.  I thought that the latency of an infiniband interconnect was closer to 1-3 microseconds with a bandwidth in the GB/sec.  I was just wondering if there is a problem with our network settings, or if there might be an issue with the molpro build, or if this is just as good as it gets.  I attached my CONFIG file for reference.  I would appreciate any information.
> 
> 
> Benjamin J. Mintz
> Research Associate, Postdoctoral
> Oak Ridge Leadership Computing Facility (OLCF)
> Oak Ridge National Laboratory
> Phone: (865) 574-6639
> Email: mintzbj at ornl.gov
> Gmail: bm0037 at gmail.com
> 
> 
> 
> ------------------------------------------------------------------------
> 
> _______________________________________________
> Molpro-user mailing list
> Molpro-user at molpro.net
> http://www.molpro.net/mailman/listinfo/molpro-user

-- 
-----------
Manhui  Wang
School of Chemistry, Cardiff University,
Main Building, Park Place,
Cardiff CF10 3AT, UK