What types of EnergyPlus models benefit from using multiple threads?

The documentation for the ProgramControl object states that some portions of EnergyPlus are able to use more than one processor. So firstly, which portions of the code are able to take advantage of this?

And secondly, what types of models are likely to run faster when the Number of Threads Allowed field is set to 0 to use all threads rather set to run on a single thread? Do models with more or less complex geometry benefit? More or less complex HVAC systems? Specific objects or combinations of objects?

The only part of EnergyPlus that was multi-threaded was the interior radiant exchange calculation, which was parallelized across zones. Large multi-zone models benefited from this when EnergyPlus ran as the sole application on a multi-core machine. However, the implementation (OpenMP) was such that there was a 5-10% performance "tax" just to compile in the parallel code. There was also the problem that slowdowns were observed when multiple EnergyPlus simulations were run in parallel or when EnergyPlus was running alongside other computationally-intensive applications. Because of these drawbacks (primarily the first one), this feature has been disabled in more recent versions. <EPDevHat>We may revisit it in the future now that we are able to use lower-overhead C++ threads rather than OpenMP, but we are working on other, more robust and lower-overhead performance improvements first.</EPDevHat>

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__AmirRoth__

answered 2014-11-28 16:18:26 -0500