Reduce

Syntax

reduce[root,operation]

Semantics

All processes in the group will combine their values together at the root process and then the operation will be performed on them.

Example

var t:Int::allocated[multiple[]];
var x:Int::allocated[multiple[]];
var p;
par p from 0 to 3 {
   x:(x::reduce[1,"max"];
   x:=p;
   t:=x;
};

In this example, x is to be reduced, with the root as process 1 and the operation will be to find the maximum number. In the first assignment x:=p all processes will combine their values of p and the maximum will be placed into process 1's x. In the second assignment t:=x processes will combine their values of x and the maximum will be placed into process 1's t.

Supported operations

Operator	Description
max	Identify the maximum value
min	Identify the minimum value
sum	Sum all the values together
prod	Generate product of all values