Barrier - Maple Help

Grid

 Barrier
 block until all processes have reached this routine

 Calling Sequence Barrier()

Description

 • The Barrier command blocks all jobs initiated by the Launch command until all processes have executed the Barrier command.
 • This is useful for synchronizing execution.  It can be used to force node 0 to wait for all other nodes to finish computing.
 • This function is currently not available in "hpc" mode.

Examples

In this example nodes with a higher node number get more work to do than those with lower node numbers.  In fact, node 0 has virtually nothing to do and quickly exits.  Because the job is finished when node 0 is done, you will see very little or no output from the other nodes.

 > dosome := proc()    uses Grid;    local i, me;    me := MyNode();    for i from 1 to 10^(me+3) do        if i mod 10^5 = 0 then            print(me,i);        end if;    end do;    print(me,"done"); end proc:
 > $\mathrm{Grid}\left[\mathrm{Launch}\right]\left(\mathrm{dosome},\mathrm{numnodes}=4\right)$
 0, "done"                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                1, "done"                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                3, 100000                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                2, 100000                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                2, "done"                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                3, 200000                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                3, 300000                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                3, 400000                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                3, 500000

This procedure is identical to the one above except that a call to Barrier is added at the end of the procedure.  This will force all nodes to wait and synchronize around that point.  Unlike the previous example, this time every node has a chance to finish.

 > doall:= proc()    uses Grid;    local i, me;    me := MyNode();    for i from 1 to 10^(me+3) do        if i mod 10^5 = 0 then            print(me,i);        end if;    end do;    print(me,"done");    Barrier(); end proc:
 > $\mathrm{Grid}\left[\mathrm{Launch}\right]\left(\mathrm{doall},\mathrm{numnodes}=4\right)$
 0, "done"                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                1, "done"                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                3, 100000                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                2, 100000                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                2, "done"                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                3, 200000                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                3, 300000                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                3, 400000                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                3, 500000                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                3, 600000                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                3, 700000                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                3, 800000                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                3, 900000                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                               3, 1000000                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                3, "done"

Compatibility

 • The Grid[Barrier] command was introduced in Maple 15.