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-   -   Two instances of lamd (http://www.cfd-online.com/Forums/openfoam-solving/59511-two-instances-lamd.html)

msrinath80 August 10, 2007 14:58

Is it possible to have two ins
 
Is it possible to have two instances of lamd on one 4 CPU machine (for instance). Then one could run two 2-CPU jobs independent of each other.

msrinath80 August 10, 2007 15:12

Got it. Using varying values o
 
Got it. Using varying values of the environment variable LAM_MPI_SESSION_SUFFIX before running lamboot.

philippose August 10, 2007 15:37

Hey Srinath, Quick question
 
Hey Srinath,

Quick question... what happens if you have a 4 CPU machine, and you run lamboot once...

And then, run "mpirun -np 2 ......." two times? Wont the Linux kernel automatically assign two processors for one "mpirun", and the other two for the second "mpirun" ??

I very often run one parallel run (with two processors...using one "mpirun -np 2 ...."), and one normal run on a Quad Core.

I have found that leaving one processor in a Quad Core free actually speeds things up, compared to a parallel run which uses all 4 processing cores....would you able to confirm that for me ?

Have a nice evening!

Philippose

msrinath80 August 10, 2007 16:36

Quick question... what happens
 
Quick question... what happens if you have a 4 CPU machine, and you run lamboot once...

And then, run "mpirun -np 2 ......." two times? Wont the Linux kernel automatically assign two processors for one "mpirun", and the other two for the second "mpirun" ??

Frankly, I don't know! I think it depends on how many nodes you specified in the machines file you supplied to lamboot.

With regards to the quad-core, my analysis can be found here[1].

Hope that helps!

[1] http://www.cfd-online.com/OpenFOAM_D...tml?1181823034

philippose August 10, 2007 17:05

Hmmmm..... When you use "mpiru
 
Hmmmm..... When you use "mpirun -np <n>", you dont need to specify the number of nodes for the lamboot command....

I usually use a file called "machines", in which I put in the IP of the machine I use... example:

127.0.0.1

Thats it... and then... "lamboot -v machines"

Specification of the number of nodes is done in the "mpirun -np <n>" command.

Anyway... shall try this out on Monday... no access to the Quad core over the weekend.

Have a nice weekend!

Philippose

msrinath80 August 10, 2007 17:10

I'm pretty sure of one thing t
 
I'm pretty sure of one thing though. One instance of the LAM daemon (lamd) cannot support two separate MPI instances. Otherwise I wonder why would they provide for a LAM_MPI_SESSION_SUFFIX variable?

Anyways, I eagerly look forward to your quad-core results.


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