Author: larry Date: Thu Jun 15 16:38:12 2006 New Revision: 9662 Modified: doc/trunk/design/syn/S03.pod
Log: Semantics of the hyperop "promise" with respect to optimization possibilities. Modified: doc/trunk/design/syn/S03.pod ============================================================================== --- doc/trunk/design/syn/S03.pod (original) +++ doc/trunk/design/syn/S03.pod Thu Jun 15 16:38:12 2006 @@ -12,9 +12,9 @@ Maintainer: Larry Wall <[EMAIL PROTECTED]> Date: 8 Mar 2004 - Last Modified: 11 Jun 2006 + Last Modified: 15 Jun 2006 Number: 3 - Version: 38 + Version: 39 =head1 Changes to existing operators @@ -430,6 +430,30 @@ allow dependencies that assume top-down visitation and only leaves sibling calls unordered.]) +Even in the absence of hardware that can do parallel processing, +hyperoperators may be faster than the corresponding scalar operators +if they can factor out looping overhead to lower-level code, or +can apply loop-unrolling optimizations, or can factor out some or +all of the MMD dispatch overhead, based on the known types of the +operands (and also based on the fact that hyper operators promise +no interaction among the "iterations", whereas the corresponding +scalar operator in a loop cannot make the same promise unless all +the operations within the loop are known to be side-effect free.) + +In particular, infix hyperops on two C<int> or C<num> arrays need +only do a single MMD dispatch to find the correct function to call for +all pairs, and can further bypass any type-checking or type-coercion +entry points to such functions when there are known to be low-level +entry points of the appropriate type. (And similarly for unary C<int> +or C<num> ops.) + +Application-wide analysis of finalizable object types may also enable +such optimizations to be applied to C<Int>, C<Num>, and such. In the +absence of that, run-time analysis of partial MMD dispatch may save +some MMD searching overhead. Or particular object arrays might even +keep track of their own run-time type purity and cache partical MMD +dispatch tables when they know they're likely to be used in hyperops. + =head1 Reduction operators The other metaoperator in Perl 6 is the reduction operator. Any
