UnorderedCopy¶

Usage

use UnorderedCopy;

This module provides an unordered version of copy/assign for numeric types. The results from this function are not visible until task or forall termination or an explicit unorderedCopyFence(), but it can provide a significant speedup for bulk assignment operations that do not require ordering of operations:

use BlockDist, UnorderedCopy;

const size = 10000;
const space = {0..size};
const D = space dmapped Block(space);
var A, reversedA: [D] int = D;

forall i in D do
  unorderedCopy(reversedA[i], A[size-i]);

// no fence required, fenced at task/forall termination

forall (rA, i) in zip(reversedA, D) do
  assert(rA == size-i);

It's important to be aware that unordered operations are not consistent with regular operations and updates may not be visible until the task or forall that issued them terminates or an explicit unorderedCopyFence().

var a = 0;
on Locales[1] {
  var b = 1;
  unorderedCopy(b, a);
  writeln(b);        // can print 0 or 1
  unorderedCopyFence();
  writeln(b);        // must print 0
}

Generally speaking they are useful for when you have a large batch of remote assignments to perform and the order of those operations doesn't matter.

proc unorderedCopy(ref dst, ref src): void¶

Unordered copy. Only supported for numeric types.

proc unorderedCopyFence(): void¶

Fence any pending unordered copies. Note that this is a global fence across all locales.