LanX has asked for the wisdom of the Perl Monks concerning the following question:
Hi
the following code was intended to show to my colleagues that hash-slices are faster than maps.
What's surprising me is that a variant with explicit keys is always faster than using a constant list.
And the latter is slower than using a variable array!!!
Please note that B::Deparse doesn't show any code difference (haven't run it through B::Concise yet)
What am I doing wrong?
-*- mode: compilation; default-directory: "d:/Users/LanX/vm_share/pm/" + -*- Compilation started at Wed Mar 13 13:03:10 C:/Perl_524/bin\perl.exe d:/Users/LanX/vm_share/pm/benchmark_slice.pl + Smartmatch is experimental at d:/Users/LanX/vm_share/pm/benchmark_slic +e.pl line 60. hash %h: { xxxxa => 12345, xxxxb => 12346, xxxxc => 12347, xxxxd => 12348, xxxxe => 12349, xxxxf => 12350, } Rate map_const map_var slice_const slice_var slic +e_explicit map_const 326753/s -- -36% -86% -87% + -88% map_var 511706/s 57% -- -78% -79% + -82% slice_const 2284993/s 599% 347% -- -6% + -18% slice_var 2423666/s 642% 374% 6% -- + -14% slice_explicit 2802527/s 758% 448% 23% 16% + -- ok 1 - slice_const { use warnings; use strict; no feature ':all'; use feature ':5.12'; join ',', @h{'xxxxa', 'xxxxb', 'xxxxc', 'xxxxd', 'xxxxe', 'xxxxf'} +; } ok 2 - map_const ok 3 - map_var ok 4 - slice_var ok 5 - slice_explicit { use warnings; use strict; no feature ':all'; use feature ':5.12'; join ',', @h{'xxxxa', 'xxxxb', 'xxxxc', 'xxxxd', 'xxxxe', 'xxxxf'} +; } 1..5 Compilation finished at Wed Mar 13 13:03:55
use 5.012; use strict; use warnings; use Data::Dump qw/pp dd/; use Benchmark qw( cmpthese ) ; use Test::More; use B::Deparse; my $deparse = B::Deparse->new(); use constant SHOW_DEPARSE => 1; my (@keys, @values, %h, $expected); BEGIN { my $n_keys = 6; my ( $first_key, $first_value ) = ("xxxxa",12345); push @keys, $first_key++ for 1.. $n_keys; push @values, $first_value++ for 1.. $n_keys; @h{@keys} = @values; # init hash $expected = join ",", @values; eval <<"__CODE__"; sub slice_explicit { join ",", \@h{ qw/@keys/} } __CODE__ } warn "hash %h: ", pp(\%h) ,"\n"; use constant LIST=>(@keys); my @list= @keys; my $h_subs = { map_var => sub{ join ",", map { $h{$_} } @list }, map_const => sub{ join ",", map { $h{$_} } LIST }, slice_var => sub{ join ",", @h{@list} }, slice_const => sub{ join ",", @h{LIST()} }, slice_explicit => \&slice_explicit, } ; cmpthese( -5, $h_subs ); # --- test validity while ( my ($name,$sub) = each %$h_subs ) { my $result = $sub->(); is($result, $expected, $name); # --- show code say $deparse->coderef2text($sub) if SHOW_DEPARSE and $name ~~ [qw/slice_const slice_explicit/]; } done_testing();
Cheers Rolf
(addicted to the Perl Programming Language :)
Wikisyntax for the Monastery
FootballPerl is like chess, only without the dice
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Replies are listed 'Best First'. | |
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Re: Benchmark: Constant List in Hash Slice
by dave_the_m (Monsignor) on Mar 13, 2019 at 14:10 UTC | |
by LanX (Saint) on Mar 13, 2019 at 17:38 UTC | |
by LanX (Saint) on Mar 14, 2019 at 12:03 UTC | |
by dave_the_m (Monsignor) on Mar 14, 2019 at 15:01 UTC | |
by LanX (Saint) on Mar 14, 2019 at 15:33 UTC | |
Re: Benchmark: Constant List in Hash Slice
by tobyink (Canon) on Mar 13, 2019 at 14:18 UTC | |
Re: Benchmark: Constant List in Hash Slice
by hdb (Monsignor) on Mar 13, 2019 at 12:29 UTC | |
by LanX (Saint) on Mar 13, 2019 at 13:13 UTC |
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