Difference between revisions of "Reduce"
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All processes in the group will combine their values together at the root process and then the operation will be performed on them. | All processes in the group will combine their values together at the root process and then the operation will be performed on them. | ||
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== Example == | == Example == | ||
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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''. | 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 == | ||
| + | |||
| + | {{ Template:ReductionOperations }} | ||
[[Category:Type Library]] | [[Category:Type Library]] | ||
[[Category:Composite Types]] | [[Category:Composite Types]] | ||
[[Category:Primitive Communication Types]] | [[Category:Primitive Communication Types]] | ||
Revision as of 17:27, 12 January 2013
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 |
