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Parameteric vs. Batch vs. Cluster sweeps
Posted 13.08.2014, 01:03 GMT-4 Cluster & Cloud Computing, Parameters, Variables, & Functions, Studies & Solvers Version 4.4 4 Replies
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I have a time-dependent model and I would like to sweep through a range of values of one of the model parameters. The problem is an 'embarrisingly parrallel problem' and very much similar to the example given in this COMSOL blog post:
www.comsol.com/blogs/added-value-task-parallelism-batch-sweeps/
However after much reading on the support pages and in the reference manual, I am still not quite sure how COMSOL handles the various sweep study options:
1. Parametric Sweep
2. Batch Sweep
3. Cluster Sweep
I'm a bit confused because I have managed to use the Batch Sweep to solve the model on our computational cluster. So then how is a Cluster sweep different to a Batch sweep? When is it advantageous to use over the other?
Regards
Amr
Hello Amr Al Abed
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A parametric sweep is performed within the COMSOL Multiphysics GUI, so you have to have the software up and running.
A batch sweep is the same as a parametric sweep, but you simply run the software from the command line, without the GUI. Functionally, is is equivalent to the parametric sweep, it will take the same time to do a batch sweep as a parametric sweep. For details on this, please see:
www.comsol.com/blogs/how-to-run-simulations-in-batch-mode-from-the-command-line/
You can also launch a batch sweep from within the GUI itself, and keep working within the GUI. For details on this, please see: www.comsol.com/blogs/the-power-of-the-batch-sweep/
A cluster sweep is only available if you're using a Floating Network License type (www.comsol.com/products/licensing) and lets you solve on a cluster. That is, different nodes of the cluster will be solving different parameters, in parallel. So, a parametric sweep (or batch sweep) run on a single computer would solve all of the different sweep values sequentially (say 1000 different parameters, one after another.) A cluster sweep could distribute those 1000 different parameters onto, e.g. 100 different nodes, solving only 10 parameters on each cluster node, in parallel. This would cut total runtime by ~100-fold.
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Functionally, is is equivalent to the parametric sweep, it will take the same time to do a batch sweep as a parametric sweep.
Walter is that correct? Shouldn't a small model run faster in a batch sweep? E.g. we have four parameter values, we allow 4 parallel processes on a 4 core machine and allow 1 core per process?
Cheers
Edgar
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Edgar J. Kaiser
emPhys Physical Technology
www.emphys.com