What are the benefits and drawbacks associated with OpenMP?
As mentioned above, the principle benefit to using OpenMP is that it can decrease memory requirements, with, in most cases, almost equal performance. There are also several other benefits, including: • Potential additional parallelization opportunities on top of those exploited by MPI; • Less domain decomposition, which can help with load balancing as well as allowing for larger messages and fewer tasks participating in MPI collective operations; • OpenMP is a standard, so any modifications introduced into an application are portable and appear as comments on systems not using OpenMP; • OpenMP can be added to a code somewhat incrementally, almost on a loop-by-loop basis, by adding annotations to existing code and using a compiler option. If you have a code that vectorizes well the vector loops are good candidates for OpenMP. There are also some potential drawbacks: • OpenMP can be hard to program and/or debug in some cases; • When using more than six threads on Hopper it is very import
