The MPI datatype hash code was developed by Julien Langou and George Bosilca, University of Tennessee, and is used with permission under the following license:
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 This is similar to the method described in "Collective Error Detection for MPI Collective Operations", Chris Falzone, Anthony Chan, Ewing Lusk, William Gropp, http://www.mcs.anl.gov/~gropp/bib/papers/2005/collective-checking.pdf
 "Hash functions for MPI datatypes", Julien Langou, George Bosilca, Graham Fagg, Jack Dongarra, http://www.cs.utk.edu/~library/TechReports/2005/ut-cs-05-552.pdf