[32819] in Perl-Users-Digest
Perl-Users Digest, Issue: 4084 Volume: 11
daemon@ATHENA.MIT.EDU (Perl-Users Digest)
Tue Nov 26 09:09:37 2013
Date: Tue, 26 Nov 2013 06:09:02 -0800 (PST)
From: Perl-Users Digest <Perl-Users-Request@ruby.OCE.ORST.EDU>
To: Perl-Users@ruby.OCE.ORST.EDU (Perl-Users Digest)
Perl-Users Digest Tue, 26 Nov 2013 Volume: 11 Number: 4084
Today's topics:
Re: Several Topics - Nov. 19, 2013 <whynot@pozharski.name>
Digest Administrivia (Last modified: 6 Apr 01) (Perl-Users-Digest Admin)
----------------------------------------------------------------------
Date: Tue, 26 Nov 2013 09:31:19 +0200
From: Eric Pozharski <whynot@pozharski.name>
Subject: Re: Several Topics - Nov. 19, 2013
Message-Id: <slrnl98ji7.4dm.whynot@orphan.zombinet>
with <87d2lpw1bf.fsf@new.chromatico.net> Charlton Wilbur wrote:
*SKIP*
> The time hit I expect isn't in allocation; it's in copying.
That allocation is such a SOB.
> If I have @foo with 1000 strings, and I say @bar = reverse @foo, that
> requires copying 1000 strings, no?
I'm not that sure:
#!/usr/bin/perl
use strict;
use warnings;
use Benchmark qw{ cmpthese timethese };
my @aa = 1 .. 10e5;
my @ab;
cmpthese timethese -5, {
code00 => sub { @ab = map -$_, reverse @aa },
code01 => sub { @ab = reverse @aa; $_ = -$_ foreach @ab },
};
__END__
Benchmark: running code00, code01 for at least 5 CPU seconds...
code00: 6 wallclock secs ( 5.36 usr + 0.02 sys = 5.38 CPU) @ 2.04/s (n=11)
code01: 5 wallclock secs ( 5.12 usr + 0.02 sys = 5.14 CPU) @ 3.31/s (n=17)
Rate code00 code01
code00 2.04/s -- -38%
code01 3.31/s 62% --
With ten time smaller list -- ten time faster, same ratio.
p.s. With 10e6 I can't even start moving bits around -- VSZ doesn't fit
in physical memory.
--
Torvalds' goal for Linux is very simple: World Domination
Stallman's goal for GNU is even simpler: Freedom
------------------------------
Date: 6 Apr 2001 21:33:47 GMT (Last modified)
From: Perl-Users-Request@ruby.oce.orst.edu (Perl-Users-Digest Admin)
Subject: Digest Administrivia (Last modified: 6 Apr 01)
Message-Id: <null>
Administrivia:
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End of Perl-Users Digest V11 Issue 4084
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