Re^3: Unhappy returns

Using map is a lot of overhead for just assigning to a hash.

use Benchmark;
timethese(1000, {
    'map1' => sub {
        my %str = map {($_,1)} (0..1024);
    },
    'arry' => sub {
        my %str = ();
        @str{0..1024} = (1)x1025;
    }
});

Benchmark: timing 1000 iterations of arry, map1...
      arry:  1 wallclock secs ( 1.36 usr +  0.00 sys =  1.36 CPU) @ 73
+5.29/s (n=1000)
      map1:  3 wallclock secs ( 3.11 usr +  0.00 sys =  3.11 CPU) @ 32
+1.54/s (n=1000)
[download]

Comment on Re^3: Unhappy returns Download Code

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Re^4: Unhappy returns by dragonchild (Archbishop) on Oct 10, 2005 at 17:32 UTC
Overhead how? Depending on what I'm doing, hash-slicing might be harder to maintain than map. `my %is_month_abbrev = map { $_ => undef } qw( jan feb mar apr may jun jul aug sep oct nov dec ); # versus ... my %is_month_abbrev; @is_month_abbrev{ qw( jan feb mar apr may jun jul aug sep oct nov dec +) } = (undef) x 12; # or, with an intermediate array ... my @months = qw( jan feb mar apr may jun jul aug sep oct nov dec ); my %is_month_abbrev; @is_month_abbrev{@months} = (undef) x @months;` [download] Often, losing a few micro-seconds is worth readability and maintainability. In both the slicing solutions, I either needed a separate array or hard-coding a magic number. (The number of months in a year isn't always a given. Some calendars have as few as 10, others have up to 14, and still others vary from year to year.) My criteria for good software: Does it work? Can someone else come in, make a change, and be reasonably certain no bugs were introduced?	[reply] [d/l]
Re^4: Unhappy returns by Perl Mouse (Chaplain) on Oct 10, 2005 at 16:00 UTC
That of course depends entirely on what you do with in the map. I used constant values of 1 just to illustrate my point, and to keep the example as simple as possible. `Perl --((8:>*`	[reply]