Sun MPI 4.0 User's Guide: With CRE

Numerics

MPI_CANONREDUCE

Prevents reduction operations from using any optimizations that take advantage of the physical location of processors. This may provide more consistent results in the case of floating-point addition, for example. However, the operation may take longer to complete. The default value is 0, meaning optimizations are allowed. To prevent optimizations, set the value to 1.