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Implement the sort pragma. Split sort code from pp_ctl.c
to pp_sort.c. Includes the quicksort stabilizing layer from John P. Linderman. -Msort=qsort or -Msort=fast is faster than without (or with -Msort=mergesort or -Msort=safe) for short random inputs, but for some reason not quite as fast as 5.6.1 qsort. More benchmarking, profiling, tuning, and optimizing definitely needed. p4raw-id: //depot/perl@13179
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,111 @@ | ||
| package sort; | ||
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| our $VERSION = '1.00'; | ||
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| $sort::hint_bits = 0x00020000; # HINT_LOCALIZE_HH, really... | ||
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| $sort::quicksort_bit = 0x00000001; | ||
| $sort::mergesort_bit = 0x00000002; | ||
| $sort::sort_bits = 0x000000FF; # allow 256 different ones | ||
| $sort::stable_bit = 0x00000100; | ||
| $sort::insensitive_bit = 0x00000200; | ||
| $sort::safe_bits = 0x00000300; | ||
| $sort::fast_bit = 0x00000400; | ||
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| use strict; | ||
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| sub import { | ||
| shift; | ||
| if (@_ == 0) { | ||
| require Carp; | ||
| Carp::croak("sort pragma requires arguments"); | ||
| } | ||
| $^H |= $sort::hint_bits; | ||
| local $_; | ||
| while ($_ = shift(@_)) { | ||
| if (/^q(?:uick)?sort$/) { | ||
| $^H{SORT} &= ~$sort::sort_bits; | ||
| $^H{SORT} |= $sort::quicksort_bit; | ||
| return; | ||
| } elsif ($_ eq 'mergesort') { | ||
| $^H{SORT} &= ~$sort::sort_bits; | ||
| $^H{SORT} |= $sort::mergesort_bit; | ||
| return; | ||
| } elsif ($_ eq 'safe') { | ||
| $^H{SORT} &= ~$sort::fast_bit; | ||
| $^H{SORT} |= $sort::safe_bits; | ||
| $_ = 'mergesort'; | ||
| redo; | ||
| } elsif ($_ eq 'fast') { | ||
| $^H{SORT} &= ~$sort::safe_bits; | ||
| $^H{SORT} |= $sort::fast_bit; | ||
| $_ = 'quicksort'; | ||
| redo; | ||
| } else { | ||
| require Carp; | ||
| Carp::croak("sort: unknown subpragma '@_'"); | ||
| } | ||
| } | ||
| } | ||
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| sub current { | ||
| my @sort; | ||
| if ($^H{SORT}) { | ||
| push @sort, 'quicksort' if $^H{SORT} & $sort::quicksort_bit; | ||
| push @sort, 'mergesort' if $^H{SORT} & $sort::mergesort_bit; | ||
| push @sort, 'safe' if $^H{SORT} & $sort::safe_bits; | ||
| push @sort, 'fast' if $^H{SORT} & $sort::fast_bit; | ||
| } | ||
| push @sort, 'mergesort' unless @sort; | ||
| join(' ', @sort); | ||
| } | ||
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| 1; | ||
| __END__ | ||
| =head1 NAME | ||
| sort - perl pragma to control sort() behaviour | ||
| =head1 SYNOPSIS | ||
| use sort 'quicksort'; | ||
| use sort 'mergesort'; | ||
| use sort 'qsort'; # alias for quicksort | ||
| # alias for mergesort: insenstive and stable | ||
| use sort 'safe'; | ||
| # alias for raw quicksort: sensitive and nonstable | ||
| use sort 'fast'; | ||
| my $current = sort::current(); | ||
| =head1 DESCRIPTION | ||
| With the sort pragma you can control the behaviour of the builtin | ||
| sort() function. | ||
| In Perl versions 5.6 and earlier the quicksort algorithm was used to | ||
| implement sort(), but in Perl 5.8 the algorithm was changed to mergesort, | ||
| mainly to guarantee insensitiveness to sort input: the worst case of | ||
| quicksort is O(N**2), while mergesort is always O(N log N). | ||
| On the other hand, for same cases (especially for shorter inputs) | ||
| quicksort is faster. | ||
| In Perl 5.8 and later by default quicksort is wrapped into a | ||
| stabilizing layer. A stable sort means that for records that compare | ||
| equal, the original input ordering is preserved. Mergesort is stable; | ||
| quicksort is not. | ||
| The metapragmas 'fast' and 'safe' select quicksort without the | ||
| stabilizing layer and mergesort, respectively. In other words, | ||
| 'safe' is the default. | ||
| Finally, the sort performance is also dependent on the platform | ||
| (smaller CPU caches favour quicksort). | ||
| =cut | ||
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,17 @@ | ||
| #!./perl | ||
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| BEGIN { | ||
| chdir 't' if -d 't'; | ||
| @INC = '../lib'; | ||
| } | ||
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| use Test::More tests => 2; | ||
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| BEGIN { | ||
| require "sort.pm"; # require sort; does not work | ||
| ok(sort::current() eq 'mergesort'); | ||
| } | ||
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| use sort 'fast'; | ||
| ok(sort::current() eq 'quicksort fast'); | ||
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