Hi,
Is there an idiomatic way to find a max value in parallel iteration? I may
have missed something in existing runtime / examples, but because of
intents, finding the max without some tricks doesn't seem obvious.
Consider the following:
use Random;
var seed = 17;
var rand = new RandomStream(seed);
proc getNext(): real {
return rand.getNext();
}
// It would be nice if Chapel max took an array, as it can be smarter in
different contexts
proc _max(m): real {
if (m.domain.low > m.domain.high) then return min(real);
return max(m(m.domain.low), _max(m[m.domain.low+1..]));
}
var m: atomic real;
// would like to have a way to get the max out of this forall w/o explicit
atomic logic
forall 1..100 {
var n = getNext();
while (n > m.read()) {
m.compareExchange(m.read(), n);
}
}
writeln("max value is: ", m.read());
// works but not parallel and allocates memory
rand = new RandomStream(seed);
var res = [i in 1..100] getNext(); // bug: can't use array expression
directly in _max()
writeln("max value is: ", _max(res));
Thanks!
Brian
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