Author: lwall
Date: 2010-06-19 04:55:36 +0200 (Sat, 19 Jun 2010)
New Revision: 31373
Modified:
docs/Perl6/Spec/S03-operators.pod
Log:
[S03] explain more about the relationship of hypers with lazy infinitude
Modified: docs/Perl6/Spec/S03-operators.pod
===================================================================
--- docs/Perl6/Spec/S03-operators.pod 2010-06-19 02:24:36 UTC (rev 31372)
+++ docs/Perl6/Spec/S03-operators.pod 2010-06-19 02:55:36 UTC (rev 31373)
@@ -15,8 +15,8 @@
Created: 8 Mar 2004
- Last Modified: 15 Jun 2010
- Version: 209
+ Last Modified: 18 Jun 2010
+ Version: 210
=head1 Overview
@@ -4222,6 +4222,23 @@
@array[0...@array], @array[*-1] xx *
+Note that hypers promise that you don't care what order the processing
+happens in, only that the resulting structure ends up in a form consistent
+with the inputs. There is no promise from the system that the operation
+I<will> be parallelized. Effective parallelization requires some means
+of partitioning the work without doing more extra work than you save.
+This will differ from structure to structure. In particular, infinite
+structures cannot be completely processed, and the system is allowed to
+balance out the demands of laziness with parallel processing. For instance,
+an algorithm that wants to divide a list into two equal sublists will not
+work if you have to calculate the length in advance, since you can't always
+calculate the length. Various approaches can be taken: handing off batches
+to be processed in parallel on demand, or interleaving roundrobin with a
+set of N processors, or whatever. In the limit, a simple, non-parallel,
+item-by-item lazy implementation is within spec, but unlikely to use multiple
+cores efficiently. Outside of performance requirements, if the algorithm
+depends on which of these approaches is taken, it is erroneous.
+
=head2 Reduction operators
Any infix operator (except for non-associating operators)
