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I think your benchmark is flawed. I don't think your append code is doing what you think it's doing. Witness:
my $buffer .= "x" x 1024 for 0 .. 5; print length $buffer;

$buffer is uninitialized by the time it reached the print. Moving the declaration away from the assignment fixes this.

Furthermore, both fragments don't produce the same result. The 'push' variant keeps everything in an array - it ought to have final join, IMO.

Here's a somewhat different benchmark. It also shows the append method to be faster, and much faster than I expected it to be.

#!/usr/bin/perl use strict; use warnings; use Benchmark qw /cmpthese/; our $str; our ($a, $b); for our $t (5, 10, 100) { for my $n (1, 8, 64) { $str = "x" x ($n * 1024); cmpthese -3, { "append${n}k_$t" => '$::a = ""; $::a .= $::str for 1 .. $: +:t;', "push${n}k_$t" => 'my @s; push @s => $::str for 1 .. $: +:t; $::b = join "" => @s', }; die "Benchmark is wrong\n" unless length ($a) == $t * length $ +str && length ($b) == $t * length $ +str; } } __END__ Benchmark: running append1k_5, push1k_5 for at least 3 CPU seconds... Rate push1k_5 append1k_5 push1k_5 91330/s -- -58% append1k_5 219880/s 141% -- Benchmark: running append8k_5, push8k_5 for at least 3 CPU seconds... Rate push8k_5 append8k_5 push8k_5 33834/s -- -50% append8k_5 67846/s 101% -- Benchmark: running append64k_5, push64k_5 for at least 3 CPU seconds.. +. Rate push64k_5 append64k_5 push64k_5 460/s -- -92% append64k_5 5705/s 1139% -- Benchmark: running append1k_10, push1k_10 for at least 3 CPU seconds.. +. Rate push1k_10 append1k_10 push1k_10 53627/s -- -60% append1k_10 135692/s 153% -- Benchmark: running append8k_10, push8k_10 for at least 3 CPU seconds.. +. Rate push8k_10 append8k_10 push8k_10 16317/s -- -67% append8k_10 48795/s 199% -- Benchmark: running append64k_10, push64k_10 for at least 3 CPU seconds +... Rate push64k_10 append64k_10 push64k_10 221/s -- -85% append64k_10 1510/s 583% -- Benchmark: running append1k_100, push1k_100 for at least 3 CPU seconds +... Rate push1k_100 append1k_100 push1k_100 5730/s -- -60% append1k_100 14175/s 147% -- Benchmark: running append8k_100, push8k_100 for at least 3 CPU seconds +... Rate push8k_100 append8k_100 push8k_100 185/s -- -84% append8k_100 1181/s 537% -- Benchmark: running append64k_100, push64k_100 for at least 3 CPU secon +ds... Rate push64k_100 append64k_100 push64k_100 22.5/s -- -76% append64k_100 94.7/s 320% --

Abigail


In reply to Re: append to a string or make an array? (memory and time efficiency) by Abigail-II
in thread append to a string or make an array? (memory and time efficiency) by swkronenfeld

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