Allreduce Type

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The allreduce[operation] type is quite similar to the reduce type, but the reduction will be performed on each process and the result is also available to all.

Operation	Semantics
min	Find the minimum value
max	Find the maximum value
sum	Add the values up
prod	Find the product of the value
land	Compute the logical and
band	Compute the bitwise and
lor	Compute the logical or
bor	Compute the bitwise or
lxor	Compute the logical xor
bxor	Compute the bitwise xor
minloc	Find the minimum value and location
replace	Current value in the target memory is replaced by the value supplied by the origin

Examples

var x:Int::allocated[multiple[]];
var p;
par p from 0 to 3
{
(x::allreduce["min"]):=p;
};

In this case all processes will perform the reduction on p and all processes will have the minimum value of p placed into their copy of x.

Last Modified: August 2008