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| List::Gen::Benchmark(3) | User Contributed Perl Documentation | List::Gen::Benchmark(3) |
NAME
List::Gen::Benchmark - performance tips for using List::Gen
SYNOPSIS
this document contains various benchmarks comparing the parallel syntax styles that List::Gen provides.
running the benchmark
perl -MList::Gen::Benchmark
benchmark tests
iteration:
reduce: my $x = $gen->reduce(sub {$a + $b});
# same as $gen->sum
do: my $x; $gen->do(sub {$x += $_})
for: my $x; $x += $_ for @$gen;
more/next: my $x; $gen->reset;
$x += $gen->next while $gen->more;
$gen->(): my ($x, $n); $gen->reset;
$x += $n while ($n) = $gen->();
iterator: my $it = $gen->iterator;
my ($x, $n); $gen->reset;
$x += $n while ($n) = $it->();
next: my ($x, $n); $gen->reset;
$x += $n while ($n) = $gen->next;
handle: my $x; local $_; $gen->reset;
$x += $_ while <$gen>;
benchmark results
iteration:
[+] 0 .. 10:
Rate reduce do for more/next $gen->() iterator next handle
reduce 28489/s -- -8% -30% -55% -55% -67% -68% -71%
do 31109/s 9% -- -24% -51% -51% -64% -65% -69%
for 40877/s 43% 31% -- -35% -35% -53% -55% -59%
more/next 62977/s 121% 102% 54% -- -0% -27% -30% -36%
$gen->() 63141/s 122% 103% 54% 0% -- -27% -30% -36%
iterator 86340/s 203% 178% 111% 37% 37% -- -4% -13%
next 90021/s 216% 189% 120% 43% 43% 4% -- -9%
handle 98964/s 247% 218% 142% 57% 57% 15% 10% --
[+] 0 .. 50:
Rate for $gen->() more/next reduce do next iterator handle
for 8762/s -- -40% -40% -41% -43% -59% -60% -63%
$gen->() 14546/s 66% -- -1% -2% -5% -31% -34% -38%
more/next 14646/s 67% 1% -- -2% -4% -31% -33% -38%
reduce 14892/s 70% 2% 2% -- -3% -30% -32% -37%
do 15278/s 74% 5% 4% 3% -- -28% -30% -35%
next 21222/s 142% 46% 45% 43% 39% -- -3% -10%
iterator 21892/s 150% 51% 49% 47% 43% 3% -- -7%
handle 23454/s 168% 61% 60% 57% 54% 11% 7% --
[+] 0 .. 100:
Rate for more/next $gen->() reduce do next iterator handle
for 4424/s -- -40% -42% -53% -53% -60% -61% -64%
more/next 7385/s 67% -- -3% -21% -21% -34% -34% -39%
$gen->() 7607/s 72% 3% -- -19% -19% -32% -32% -38%
reduce 9340/s 111% 26% 23% -- -0% -16% -17% -23%
do 9341/s 111% 26% 23% 0% -- -16% -17% -23%
next 11108/s 151% 50% 46% 19% 19% -- -1% -9%
iterator 11253/s 154% 52% 48% 20% 20% 1% -- -8%
handle 12190/s 176% 65% 60% 31% 31% 10% 8% --
[+] 0 .. 1000:
Rate for more/next $gen->() next iterator do reduce handle
for 446/s -- -39% -42% -61% -62% -62% -63% -64%
more/next 735/s 65% -- -4% -35% -37% -37% -39% -41%
$gen->() 763/s 71% 4% -- -33% -34% -34% -37% -38%
next 1131/s 153% 54% 48% -- -3% -3% -7% -9%
iterator 1164/s 161% 58% 52% 3% -- -0% -4% -6%
do 1165/s 161% 58% 53% 3% 0% -- -4% -6%
reduce 1210/s 171% 65% 58% 7% 4% 4% -- -2%
handle 1237/s 177% 68% 62% 9% 6% 6% 2% --
[+] 0 .. 10000:
Rate for more/next $gen->() next iterator do handle reduce
for 44.5/s -- -40% -42% -60% -62% -63% -64% -64%
more/next 74.0/s 66% -- -3% -34% -36% -39% -41% -41%
$gen->() 76.6/s 72% 4% -- -32% -34% -37% -38% -39%
next 113/s 153% 52% 47% -- -3% -8% -9% -10%
iterator 116/s 161% 57% 52% 3% -- -5% -7% -7%
do 122/s 174% 65% 59% 8% 5% -- -2% -3%
handle 124/s 179% 68% 62% 10% 7% 2% -- -1%
reduce 125/s 182% 70% 64% 11% 8% 3% 1% --
[+] 0 .. 100000:
Rate for more/next $gen->() next iterator reduce do handle
for 4.47/s -- -41% -42% -61% -62% -63% -64% -64%
more/next 7.55/s 69% -- -2% -34% -36% -38% -39% -40%
$gen->() 7.71/s 72% 2% -- -32% -35% -36% -38% -39%
next 11.4/s 155% 51% 48% -- -4% -6% -8% -9%
iterator 11.9/s 166% 57% 54% 4% -- -2% -4% -5%
reduce 12.1/s 170% 60% 57% 6% 2% -- -2% -4%
do 12.3/s 176% 64% 60% 8% 4% 2% -- -2%
handle 12.5/s 180% 66% 63% 10% 6% 4% 2% --
interpretation
once the generator size gets large enough to mask differences in initialization code, the access methods fall into 4 classes.
- 1: " for "
- while it is one of the most perlish ways to write the loop, the " $x += $_ for @$gen " construct uses a tied array, and unfortunately ties are fairly slow. all of the other constructs use the exact same underlying " FETCH " and " FETCHSIZE " methods that the tied array uses, yet they are all much faster.
- 2: "more/next, $gen->()"
- these are almost the same speed, and are the slowest of the non-tied access methods. the " more/next " pair results in unneeded function calls, since " next " is checking the " more " condition already. the overloaded dereference has some interpreter overhead.
- 3: " next, iterator, reduce, do "
- these are the faster ways to access generators, the ranking of which
depends on the size of the generator. " next
" and " iterator " are
almost the same, and are fast across the size range.
" iterator " will always be slightly
faster than " next " since it is the
function used internally by " next"
" reduce " and " do " both have slower start-up time than " next " or " iterator " due to a bit of initialization code. this initialization code allows for their loops to be optimized further, which lets " reduce " and " do " achieve higher speeds for larger generators.
- 4: " handle "
- handle iteration in a while loop is heavily optimized by perl, and is subsequently one of the fastest techniques for iterating over a generator, and this speed is independent of generator size.
in summary, stick to " next, iterator, reduce, do, or handle " iteration styles if performance is a concern.
AUTHOR
Eric Strom, "<asg at cpan.org>"
COPYRIGHT & LICENSE
copyright 2009-2011 Eric Strom.
this program is free software; you can redistribute it and/or modify it under the terms of either: the GNU General Public License as published by the Free Software Foundation; or the Artistic License.
see http://dev.perl.org/licenses/ for more information.
| 2024-05-13 | perl v5.40.2 |
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