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Author Topic: How to power FDS or Pyrosim from multiple computers  (Read 5613 times)

davids

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How to power FDS or Pyrosim from multiple computers
« on: April 06, 2010, 03:37:28 pm »

Here is the scenario:

I have four computers. Two of them running windows 7 and the other two running windows xp. I want to run a model but it is estimated to take 800 hours. I was hoping I could cut this process time with more computer power. But I do not have a single clue how to do this.

Appreciate any help!
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Charlie Thornton

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Re: How to power FDS or Pyrosim from multiple computers
« Reply #1 on: April 07, 2010, 08:20:19 am »

FDS has 3 ways you can run:

1. Serial - FDS runs the entire problem in a single process.  This is the "normal" way to run when you''re starting out.

2. OpenMP - The FDS code has been instrumented to run various processing loops using multiple threads.  This way lets you take advantage of multiple processors on a single computer, but it''s very fine-grained and doesn''t usually give as much speedup as MPI*.

3. MPI - Each mesh is run in a separate process.  Processes can be spread out across multiple computers on a network.  From data I''ve collected, this generally gives the fastest simulations assuming your meshes are of similar size (cell count).

* - Here is some performance data we collected for different parallel approaches: http://www.pyrosim.com/benchmarks.html  Have a look at the Simulation Run Time table.

PyroSim supports all three modes, but only on a single computer.  To take advantage of multiple computers on a network, you''ll need to run FDS by hand.  This isn''t really so bad and the process is pretty well explained in the FDS Users Guide, section 3.1.2: Starting an FDS Calculation (Multiple Processor Version).

To get your FDS input file out of PyroSim: On the File menu, click Export, then click FDS File...  After exporting the FDS file, follow the instructions in FDS Users Guide to run a parallel problem.  When you''re finished, you can run smokeview from the command line, or from within PyroSim -- ultimately both approaches just start smokeview.exe
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