Newsgroups: comp.parallel.pvm
From: coxt@tempest.adsnet.net (Tom Cox)
Subject: Re: How many tasks can one spawn on a single host
Organization: Wolfe Internet Access, L.L.C.
Date: Fri, 17 Nov 1995 07:01:57 GMT
Message-ID: <48hcd6$fao@news1.wolfe.net>

Chetan N Vora <chet@brc.uconn.edu> wrote:

>Hi everyone,

>I am trying to build a parallel MD code using the master-slave paradigm.
>Currently, I am using two Sparcstation 2000 with 8 cpus each connected with
>Ethernet. I am having the following problems.

>Problem 1: My code runs fine when I run it on a single host and spawn less than
>6 slaves processes.But it gives me the libpvm error -
>"libpvm [task number]: peer_conn() shmat to t40006: Too many open files" 
>when I spawn more than 5 tasks.

>What does this message mean ?? I get this error only when the no. of slaves
>exceed 5 ; the program does go to completion but doesn't give correct results
>(because of incomplete computations, I guess.) Is there any heuristic metric
>about how many tasks should one spawn on a host ??

>Problem 2: When I add the other host to the configuration and try to spawn
>tasks using PvmTaskDefault, the code just hangs. 

>Symptoms:
>The log file on host on which I started the console shows the tasks to be
>spawned with some task(s) having the error
>"libpvm[task number]: mroute() frag with no message".

>It appears that this task(s) doesn't receive at all the stuff that the master
>sends it.

>Is there any documentation about the meaning of the error messages that are
>returned in the log file ??

>Any help will be great appreciated.

>Thanks in advance,
>Chet

> 
>-- 
>*******************************************************************************
>Chetan Vora		www: http://www.eng2.uconn.edu/~chet
>The scientific theory I like the most is that Saturn's rings are composed 
>entirely of lost airline baggage.  -Mark Russel
>*******************************************************************************

We currently have the same problem on our 4 processor sun here at CWU.
We get the exact same reported errors if we try to spawn 5 or more
processes.   Any ideas?

-tom cox
coxt@tahoma.cwu.edu
Systems Analyst/Programmer I




