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Running OpenFOAM in parallel with different locations for each process

Posted December 15, 2011 at 17:56 by wyldckat

The other day a fellow forum user asked me for help about a problem dealing with the specific configuration of a case for running in a cluster. The specific configuration was simple: each slave machine of the cluster has it's own independent storage address on a similar path.
Below is an edited version of the reply I sent him.


OK, first detail - In the following file you have a (sort-of) well documented "decomposeParDict":
Code:
applications/utilities/parallelProcessing/decomposePar/decomposeParDict
...
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Old

Dark side of Amdahl's law. Part III

Posted December 9, 2011 at 12:04 by SergeAS
Tags mpi, parallel

...use a blocking call Sendrecv() instead of a pair of Send() + Recv() slightly improves the performance of the code but does not result to improved scalability


...
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Old

Dark side of Amdahl's law. Part II

Posted December 4, 2011 at 10:57 by SergeAS
Updated December 4, 2011 at 11:44 by SergeAS
Tags mpi, parallel

Let us consider in more detail how works domain decomposition in the simplest 1D case.
The computational domain is divided into several subdomains along one (usually the longest) dimension. The number of such subdomains usually corresponds to the number cores involved. The main data exchanges take place between neighboring subdomains. The size of transmitted data between adjacent subdomains in the general case depends on many factors (number of equations in the system, the size of the computational...
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Old

Slip/No-Slip Flow

Posted December 2, 2011 at 23:19 by MatthewSlaby

Hi, I'm Matthew.

You asked what the physical meaning of the slip/no-slip condition means.

You need to look up the term "Knudsen Number".

This is simply a reminder of what CFD is base upon.

This will give insight into your question.

Fluid Dynamics is mostly based on Continuim Mechanics which assumes that the properties of a gas or liquid can be approximated by some very simple rules.

These would be:
...
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Old

Dark side of Amdahl's law

Posted November 25, 2011 at 16:19 by SergeAS
Updated November 27, 2011 at 06:44 by SergeAS
Tags mpi, parallel

Looking the latest HPCSource I came across very well-known picture, illustrating the Amdahl's law:
S_p = \cfrac{1}{\alpha + \cfrac{1 - \alpha}{p}}


which shows the dependence of the speedup parallel code on number of processor cores for different fraction of time (\alpha \ne 0) spent in the part that was not parallelized. This diagram is interested in me for the...
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