| Date: Fri, 6 Nov 2009 03:42:10 -0500 | From: John Cowan <[email protected]> | | ... | Can it really be that it is more efficient to add four numbers in | two threads than in one thread? Somewhere, exactly where will | depend on implementation details, one must cross the line where | constant factors dominate. And that is not a point that, in the | general case, will be known.
There are many optimization choices for which the break-even point is not known. But we are not interested in operating at the point where parallel execution is the same speed as serial execution. We want to operate where parallel is faster. Implicit-concurrency doesn't mandate that any concurrency be used. And cautious application of concurrency is entirely compatible with implicit-concurrency. For instance, one might only fork threads when the subexpressions call user-defined functions, or user-defined functions whose definitions are over 40 lines long. _______________________________________________ r6rs-discuss mailing list [email protected] http://lists.r6rs.org/cgi-bin/mailman/listinfo/r6rs-discuss
