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The ALL Statement

The other major kind of parallel computer is the kind which has several separate CPUs which can be doing completely different things. YAL contains several statements supporting this type of computer, some of which are discussed here. The first is the ALL statement:

       ALL seq-1:node,seq-2:node,seq-3:node...

which instructs the computer to perform the actions set out in each sequence, simultaneously if possible. Control passes to the next statement only when all the actions in each sequence are completed.

With the ALL statement, as the sequences are part of the program in which they reside, they may use its variables. Thus, care in using the ALL statement is advised on parallel systems where the separate CPUs also have their own memories. (A CALL statement can of course appear as the only item inside a sequence in an ALL statement.)

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