Subject: CCL:G98W and dual processors on NT

From: "Jim Kress" <[email-masked]>
Date: Mon, 29 May 2000 18:12:22 -0400

On May 23 I asked the list about the "low memory" warning and significant
thrashing I get with Gaussian 98W on a dual processor NT machine.

The responses I received are given below (I even got one from Gaussian!).

I also did some testing on my computer.  It appears that G98W exhibits
interesting behavior with NT (maybe all 32 bit) systems where the swap file
exceeds (approximately) 2200MB.

I found the following:

SFS = swap file size (MB)
-M- = -M- parameter in default.rou (MB)
LMW = Low memory warning
TH = thrashing

SFS       -M-   Result
2500      960   LMW and TH
2500      250   no LMW
2200      960   no LMW

For SFS between 2200MB and 2500MB, G98W exhibits some very strange behavior.
For some SFS values (e.g 2250MB) when G98W is invoked it will respond with
an "Insufficient
free memory.  Need 4 MB minimum" error message and then terminate.

Also, as the SFS approaches 2200MB (from 2500MB) the difference between the
"memory needed" and "memory available" in the "Low Memory Warning" message
decreases.

This behavior is reminiscent of some of the disk i/o observations in G98W
that result from the 32 bit integer word size.

In addition, I have found that there is a significant interaction between
the -M- parameter in the default.rou file, the SFS, and cpu time necessary
to run the test case (qs.gjf).  Here are some results (cpu time is in
seconds):

SFS    -M-  cpu time
2000   960   106
2000     96     10
1400   960     98
1400   240     17
1400   128     11
1400     ns        8

-M- of ns implies not specified in default.rou so used G98W default
established upon installation of the software (install program stated that
default.rou set up for machine with > 48 MB memory).  Larger values of -M-
result in thrashing (SFS is fixed and larger than -M-).  It appears the
memory management in G98W is unkind to jobs that are small relative to the
value of -M-.

In any event, it appears that I've identified the source of the error
message.  Take the information as you will.

Thanks for the help from the people who responded!

Jim

Check out my web site  http://www.kressworks.com/

----- Original Message -----
From: Jim Kress <[email-masked]>
To: CCL <[email-masked]>
Sent: Tuesday, May 23, 2000 11:02 PM
Subject: CCL:G98W and dual processors on NT

> I am using G98W on a dual processor WinNT4.0SP5 machine with 1GB of RAM.
I
> do NOT specify MKL_NPROCS to be 2.
>
> However, when I run G98W, it pauses with a 'low memory' warning.  It
states
> that I need 480MB of RAM to continue (which is the amount specified in the
> default.rou file) but that I have only (approx.) 231MB.  If I allow it to
> proceed, it thrashes badly.  If I specify a memory value of LE 256MB in
the
> default.rou file, the program runs normally with no warnings or thrashing.
>
> The problem is not resolved by specification of MKL_NPROCS to be 1
>
> In all cases I am using the qs.gjf example from the C:\G98W\quick
> subdirectory.
>
> Anybody know what I need to do to get this to run properly with the larger
> default.rou memory specification?  I've asked Gaussian but they have not
> replied ...
>
> Thanks and I will summarize.
>
> Jim
>
> Check out my web site  http://www.kressworks.com/
>
>
Response 1:

I am not sure about G98W, but GAMESS would do that if the amount of the swap
space was low. It should be 2xRAM or more. With GAMESS I could run a job
with  720 MB RAM on a 768 MB machine with 2GB of swap space.

Slawomir Janicki
[email-masked]

Response 2:

Dr. Kress,

   We have attempted to model this on a Win2000 machine with 512MB and dual
processors using various sizes of virtual memory.  With small virtual memory
settings, 128MB, we do see a loss of efficiency but never a 'low memory'
warning.  Running with 750MB of virtual memory this seems to run fine with
a memory request of 400MB.

   What setting do you have in place for your virtual memory?

--

  Douglas J. Fox
  Technical Support
  Gaussian, Inc.
  [email-masked]

Response 3:

Well, I don't know what is happening. Loosing cache coherency perhaps? You
would think that GAUSSIAN could make their software SMP friendly...

Slawomir Janicki
[email-masked]

----- Original Message -----
From: "Jim Kress" <[email-masked]>
To: "Slawomir Z. Janicki" <[email-masked]>
Sent: Tuesday, May 23, 2000 11:12 PM
Subject: Re: G98W and dual processors on NT

> Thanks for the info.
>
> Actually, pcGAMESS is my preferred software.  Unfortunately, pcGAMESS
> doesn't have DFT capabilities and that is why I'm using G98W.
>
> Also, it's not a matter of swap space.  I have 2.5GB of swap to go with
the
> 1GB of RAM.  I never had these problems with G98W until I put in the 2nd
> processor.
>
> Jim
>
> Check out my web site  http://www.kressworks.com/
>