Perl语言再学习(6): 闭包的性能

最近经常见到这种写法：

sub returning(&) {
	my ($code) = @_;
	return $code->();
}

my $ret = returning(sub{
	return 0 if $cond1;
	return 0 if $cond2;
	return 1;
});

直觉上觉得这个效率并不是很好，但是又不知道差多少，所以稍微做了个实验比了一下。 测试代码如下：

#!/usr/bin/perl

use strict;
use Benchmark qw(:all);

sub returning(&) {
	my ($code) = @_; 
	return $code->();
}

sub calc {
	my ($a, $b) = @_; 
	return $a * $a + $b * $b; 
}

sub main {

	my $r = timethese(
		10_000_000, 
		{   
			'2_flat' => q{
				my $a = int(rand(100));
				my $b = int(rand(100));
				my $c = $a * $a + $b * $b;
			},
			'3_sub' => q{
				my $a = int(rand(100));
				my $b = int(rand(100));
				my $c = calc($a, $b);
			},
			'1_closure' => q{
				my $a = int(rand(100));
				my $b = int(rand(100));
				my $c = returning(sub {
					return $a * $a + $b * $b;
				});
			},
		}   
	);  
	cmpthese $r; 
}

main();

结果如下：

Benchmark: timing 10000000 iterations of 1_closure, 2_flat, 3_sub...
 1_closure: 36 wallclock secs (36.20 usr +  0.01 sys = 36.21 CPU) @ 276166.80/s (n=10000000)
	2_flat:  6 wallclock secs ( 5.94 usr +  0.00 sys =  5.94 CPU) @ 1683501.68/s (n=10000000)
	 3_sub: 12 wallclock secs (11.86 usr +  0.00 sys = 11.86 CPU) @ 843170.32/s (n=10000000)
			   Rate 1_closure     3_sub    2_flat
1_closure  276167/s        --      -67%      -84%
3_sub      843170/s      205%        --      -50%
2_flat    1683502/s      510%      100%        --

总结：