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7.2 Global Computation Routines

  There are two global computation routines in MPI: reduce and scan. Different versions of the reduction routine are provided depending on whether the results are made available to all processes in the group, just one process, or are scattered cyclicly across the group. Common reduction operations are the evaluation of the maximum, minimum, or sum of a set of values distributed across a group of processes. The scan routines perform a parallel prefix with respect to a user-specified operation on data distributed across a specified group. If tex2html_wrap_inline570 is the data item on the process with rank i, then on completion the output buffer of this process contains the result of combining the values from the processes with rank tex2html_wrap_inline574 , i.e.,

  equation237

MPI provides a set of pre-defined functions, and a mechanism through which user-specified functions can be used in reduce and scan operations.


top500@rz.uni-mannheim.de
Tue May 28 14:38:25 PST 1996