From owner-nwchem-users  Fri Mar  3 10:59:38 2000
Received: (from majordom@localhost)
        by odyssey.emsl.pnl.gov (8.8.8+Sun/8.8.5) id KAA09788
        for nwchem-users-outgoing; Fri, 3 Mar 2000 10:52:44 -0800 (PST)
Date: Fri, 03 Mar 2000 12:54:10 -0600
From: Ricky Kendall &LTrickyk@scl.ameslab.gov>
Subject: Re: parallel job on linux cluster
To: Todd Raeker &LTraeker@umich.edu>
Cc: nwchem-users@emsl.pnl.gov
Message-id: &LT38C00A52.FE631129@scl.ameslab.gov>
Organization: Scalable Computing Laboratory, Ames Laboratory
MIME-version: 1.0
Content-type: multipart/mixed; boundary="------------C189598C13135FD686E46C1B"
X-Accept-Language: en
References: &LT200003031612.LAA12121@vivalasvegas.rs.itd.umich.edu>
Sender: owner-nwchem-users@emsl.pnl.gov
Precedence: bulk

This is a multi-part message in MIME format.
--------------C189598C13135FD686E46C1B
Content-Type: text/plain; charset=us-ascii
Content-Transfer-Encoding: 7bit

Todd,
    This seems like a problem with the network.  We have an
Alpha Cluster and I enclose a excel spreadsheet with the data
The time decreases and the speedup (walltime) gets to 50% at 8 nodes.
The only thing I would offer is the timing variance in such a short
job may be large enough to caue this.  Try something with a little
more meat in it time wise.  Also as you can tell from the spreadsheet
the CPU based scaling is quite good.  e.g., we need a better network:)
Regards,
Ricky


Todd Raeker wrote:

> Hi all,
>
>   I am testing a two node linux cluster on a 100 Mbits/sec standalone
> switched network.  A small scf single point energy calculation on one and
> two nodes results in the CPU time going from 44 sec. to 22 sec.
> respectively.  This is great but when I look at the wall time I get 44 sec.
> for one node verses 49 sec for the two node calculation.  This really
> surprises me as the local net is running at 100 Mbits/sec and completely
> isolated from other networks.  I would like to talk to anybody out there
> with experience running nwchem on linux clusters.  My hardware consists of
> two machines with a 600 MHz AMD Athlon in each with 128 MB memory, 3com905
> NIC and 3com superstack 3300 at 100 Mbits/sec network running RedHat 6.0
> Linux.  I hope the slow wall time is a mistake in my network configuration
> rather than an high amount of nwchem builtin communication between nodes
> which increases overhead.  Any advice or info would be appreciated.
>
> Todd.
>
> Dr. Todd Raeker
> Coordinator of Computer Services         raeker@umich.edu
> Department of Chemistry                     (734)647-2867
> University of Michigan
> Ann Arbor, MI 48109