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use BlockDist; | |
proc main() throws { | |
var D = {1..8}; | |
var distD = D dmapped Block(boundingBox=D); | |
var A: [distD] int; | |
// Test array (from http://mpitutorial.com/tutorials/mpi-reduce-and-allreduce/) | |
A = [5, 1, 2, 3, 7, 8, 4, 2]; | |
var ret = MPI_Reduce(A); | |
writeln(ret); | |
// Should be [18, 14] | |
MPI_Allreduce(A); | |
writeln(A); | |
// Should be [18, 14, 18, 14, 18, 14, 18, 14] | |
} | |
/* Sum ith element on each locale and place sum onto ith element on locale 0 */ | |
proc MPI_Reduce(A: [?D]) throws { | |
if D.size & numLocales != 0 then | |
throw new owned IllegalArgumentError('Array size must be evenly divisible by numLocales'); | |
const N = D.size / numLocales; | |
var results: [1..N] int; | |
forall i in results.domain { | |
results[i] = + reduce A[i.. by N]; | |
} | |
return results; | |
} | |
/* Sum ith element on each locale and place sum onto ith element of each locale */ | |
proc MPI_Allreduce(ref A: [?D]) throws { | |
var results = MPI_Reduce(A); | |
const N = D.size / numLocales; | |
forall loc in Locales { | |
const slice = (loc.id*N+1)..#N; | |
// localeSlice asserts we are writing locally | |
A.localSlice(slice) = results; | |
} | |
} |
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Tested with
-nl 4