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Subject: Re: MultiThreading on a PC
Author: Bob Weathers
Date: 1999-07-13 09:18:00

Chris,

Thanks for your reply.

I have a PC with 2 GB RAM. Unfortunately, when I run in BATCH mode, I can't
specify more than ~700 MB on the -m command. On invocation of the BATCH
run, ANSYS immediately halts saying that there's not enough memory available
if I specify >~700 MB. I can get to 1440 MB for -m if I run interactively.
George Karnos at ANSYS is looking into this but no solution has been found
so far. I observe this behavior with both 5.5.2 and 5.5.3 on my PCs running
NT 4.0 with SP4 or SP5.

-----Original Message-----
Sent: Tuesday, July 13, 1999 7:49 AM
To: xansys@o...

I had a user call-in about a very similiar problem...
ANSYS 5.5.x would "hang" when he used more than 1
processor on an Intel-based PC with NT 4.0. It did
not abort; it would just grind to a halt, i.e. CPU
usage would tend towards zero. "Small" models ran
fine; "large" ones had the problem. I can't remember
what type of analysis he was doing (and I'm too lazy
to look it up).

Anyhow, the engineers at ANSYS, Inc. debugged the
problem and the fix is in ANSYS 5.6.

According to the engineers at ANSYS, Inc. this problem
only occurs when you run ANSYS in interactive mode.
There is no problem running in batch mode. Have you
tried running in batch mode? If not, give it a try.
Otherwise, your only other workaround is to set NPROC
to 1. (There is no parallel processing for NPROC=1,
to answer another XANSYS posting.)

One caveat to John Swanson's reply to the question if
the Block Lanczos solver is parallelized: it is, at
least to a certain extent, on 64 bit SGI machines
since ANSYS 5.4. The sparse solver is parallelized on
64 bit SGI machines and the Block Lanczos solver uses
the sparse solver. On all other platforms, as John
Swanson said, the Block Lanczos solver does not yet
support parallel processing.

Chris Mollo
Automated Analysis Corp.
chris@a...

To: 'xansys'

1. Running NT 4.0 (SP4 or SP5)
2. Using ANSYS 5.5.2 or 5.5.3
3. Solving a large (~600K DOFs) modal using PowerDynamics or Block
Lanczos solvers
4. Using '/CONFIG, NPROC, 2' always caused the solution to abort before
fully solved. (Tried it 6 times on 2 PCs)
5. Omitting the preceding /CONFIG command lets a solution be obtained.

Anyone else seen this behavior on a PC?

Bob Weathers
bweathers@t...
(608)787-2729

Posts possibly associated with message #3239AuthorDateScore
3217MultiThreading on a PCBob Weathers1999/07/12 
3222Re: MultiThreading on a PCMike McNamee1999/07/12 
3223Re: MultiThreading on a PCBob Weathers1999/07/12 
3225Re: MultiThreading on a PCCosme, Carlos CCosme@1999/07/12 
3229Re: MultiThreading on a PCJohn Swanson1999/07/12 
3238Re: MultiThreading on a PCChris Mollo1999/07/13 
3239Re: MultiThreading on a PCBob Weathers1999/07/13 
3251Re: MultiThreading on a PCDoug Scott1999/07/13 
3265Re: MultiThreading on a PCChris Mollo1999/07/14 
3268Re: MultiThreading on a PCPatrick J. Sheehan pat@1999/07/14 
3270Re: MultiThreading on a PCBob Weathers1999/07/14