Two instances of lamd

msrinath80 · August 10, 2007, 15:58

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, 16:12

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

philippose · August 10, 2007, 16:37

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, 17:36

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, 18:05

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, 18:10

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.

August 10, 2007, 15:58	Is it possible to have two ins	#1
msrinath80 Senior Member Srinath Madhavan (a.k.a pUl\|) Join Date: Mar 2009 Location: Edmonton, AB, Canada Posts: 703 Rep Power: 21	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.

August 10, 2007, 16:12	Got it. Using varying values o	#2
msrinath80 Senior Member Srinath Madhavan (a.k.a pUl\|) Join Date: Mar 2009 Location: Edmonton, AB, Canada Posts: 703 Rep Power: 21	Got it. Using varying values of the environment variable LAM_MPI_SESSION_SUFFIX before running lamboot.

August 10, 2007, 16:37	Hey Srinath, Quick question	#3
philippose Senior Member Philippose Rajan Join Date: Mar 2009 Location: Germany Posts: 552 Rep Power: 25	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

August 10, 2007, 17:36	Quick question... what happens	#4
msrinath80 Senior Member Srinath Madhavan (a.k.a pUl\|) Join Date: Mar 2009 Location: Edmonton, AB, Canada Posts: 703 Rep Power: 21	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

August 10, 2007, 18:05	Hmmmm..... When you use "mpiru	#5
philippose Senior Member Philippose Rajan Join Date: Mar 2009 Location: Germany Posts: 552 Rep Power: 25	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

August 10, 2007, 18:10	I'm pretty sure of one thing t	#6
msrinath80 Senior Member Srinath Madhavan (a.k.a pUl\|) Join Date: Mar 2009 Location: Edmonton, AB, Canada Posts: 703 Rep Power: 21	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.