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Author Topic: Parallel Computing - query  (Read 6022 times)

lawrencelaw

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Parallel Computing - query
« on: August 28, 2009, 11:05:08 am »

Hi,

I have used the parallel computing on the pyrosim 2008 version and also executed it via the command prompt. I have noticed that the parallel computing using pyrosim is able to load all the cpu cores to 100% consistently while the command prompt method is loading the cpu cores with loads that varies 40 to 80%. I am trying to get the command prompt method to match the pyrosim parallel CFD run.

Would you be able to help in this matter?

The command prompt i used is as follow:-

mpiexec -n 5 fds5_mpi.exe filename.fds

Thank You
Best Regards
Lawrence Law
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Charlie Thornton

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Re: Parallel Computing - query
« Reply #1 on: September 10, 2009, 10:11:01 am »

How many meshes are in your simulation and how many CPUs does your computer have?

Here is the line that PyroSim uses to run MPI:

mpiexec -noprompt -port 52200 -priority 1:3 -channel ssm -n 5 fds5_mpi filename.fds

In particular, the "-channel ssm" flag might help your machine use memory a bit more efficiently compared to the default.

- Charlie
« Last Edit: September 11, 2009, 08:38:11 am by Charlie Thornton »
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RBRUCE

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Re: Parallel Computing - query
« Reply #2 on: March 06, 2012, 11:57:25 am »

my computer is telling me that the ssm channel does not exist
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Charlie Thornton

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Re: Parallel Computing - query
« Reply #3 on: March 06, 2012, 02:38:54 pm »

I think the ssm channel was replaced by the nemesis channel in newer versions of MPICH2. If you've installed your own MPICH2 you should try to use nemesis. The current PyroSim release uses an older, pre-nemesis version of MPI. I think we haven't upgraded because of some sort of problem getting it to work with FDS and windows authentication (not sure about that one though).

Bottom line: if you are using PyroSim's included MPI libs, the command I wrote out for lawrencelaw should work. If you are using a stand-alone MPICH2 install you should probably use a different port (pyrosim puts it on a custom port) and the nemesis channel.
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dhavener

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Re: Parallel Computing - query
« Reply #4 on: March 31, 2014, 07:56:35 am »

How many meshes are in your simulation and how many CPUs does your computer have?

Here is the line that PyroSim uses to run MPI:

mpiexec -noprompt -port 52200 -priority 1:3 -channel ssm -n 5 fds5_mpi filename.fds

In particular, the "-channel ssm" flag might help your machine use memory a bit more efficiently compared to the default.

- Charlie

Charlie,

I have a few questions about the syntax above. 

First - if I'm not using a custom port, do I need to specify one via the "-port" command?

Second - I'm curious about the "-priority" command, and whether "1:3" is a globally used setting or specific to fds/mpi/hardware confirguration/etc.

Thanks in advance.
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Charlie Thornton

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Re: Parallel Computing - query
« Reply #5 on: March 31, 2014, 08:31:21 am »

If you used the standard MPICH2 installer, I don't think you need the port argument.

The priority option sets the simulation to "below normal" priority. Though, it looks like the option we are using is the same as the default. From "mpiexec --help2":

Code: [Select]
-priority class[:level]
  set the process startup priority class and optionally level.
  class = 0,1,2,3,4   = idle, below, normal, above, high
  level = 0,1,2,3,4,5 = idle, lowest, below, normal, above, highest
  the default is -priority 1:3

The version of MPI that works with FDS6 replaced ssm with nemisis and nemisis is now MPICH2's default communication channel. With those changes, there may not be any difference between the options PyroSim's uses and the defaults.
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