What types of EnergyPlus models benefit from using multiple threads?

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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>