Defining Your Own Collective Operations

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MPI_Op_create(user_function, commute, op) 
MPI_Op_free(op) 
 
user_function(invec, inoutvec, len, datatype)

The user function should perform

inoutvec[i] = invec[i] op inoutvec[i];

for i from 0 to len-1.

user_function can be non-commutative (e.g., matrix multiply).

Up: Collective Communications in MPI Next: Sample user function Previous: Built-in Collective Computation Operations