From: <[EMAIL PROTECTED]>
> Well,
>
> All the above said answers are perfectly fine, but just to make it
> more efficient what we can do is, we can avoid the if statement or ?:
> operator.
>
> This is because whenever we go for a decision statement, it takes some
> extra processing time.
Whenever we index an array it takes some extra processing time as
well.
> A solution to avoid using if or ?: is as follows:
>
> #!/usr/bin/perl
> use strict;
>
> my @string = ("Even", "Odd");
> print $string[$ARGV[0]%2];
>
> Well it might look like the savings in time is less, but if you
> consider that this code is inside a loop which will run for several
> iterations, you are sacing lot of time.... Hence the program becomes
> more efficient.
Before you say something like this you should test it:
use Benchmark;
sub withIf {
my $number_is = '';
for (1..100000) {
if ($_ % 2) {
$number_is = 'Odd';
} else {
$number_is = 'Even';
}
}
}
sub withQm {
my $number_is = '';
for (1..100000) {
$number_is = ($_ % 2) ? 'Odd' : 'Even';
}
}
sub withIfAnd {
my $number_is = '';
for (1..100000) {
if ($_ & 1) {
$number_is = 'Odd';
} else {
$number_is = 'Even';
}
}
}
sub withQmAnd {
my $number_is = '';
for (1..100000) {
$number_is = ($_ & 1) ? 'Odd' : 'Even';
}
}
my @what = qw(Even Odd);
sub withAry {
my $number_is = '';
for (1..100000) {
$number_is = $what[$_ % 2];
}
}
sub withAryAnd {
my $number_is = '';
for (1..100000) {
$number_is = $what[$_ & 1];
}
}
timethese 100, {
withIf => \&withIf,
withQm => \&withQm,
withIfAnd => \&withIfAnd,
withQmAnd => \&withQmAnd,
withAry => \&withAry,
withAryAnd => \&withAryAnd,
}
Benchmark: timing 100 iterations of withAry, withAryAnd, withIf,
withIfAnd, withQm, withQmAnd...
withAry: 6 wallclock secs ( 5.67 usr + 0.00 sys = 5.67 CPU) @
17.63/s (n=100)
withAryAnd: 5 wallclock secs ( 5.20 usr + 0.02 sys = 5.22 CPU) @
19.16/s (n=100)
withIf: 6 wallclock secs ( 6.09 usr + 0.01 sys = 6.11 CPU) @
16.37/s (n=100)
withIfAnd: 6 wallclock secs ( 5.77 usr + 0.00 sys = 5.77 CPU) @
17.35/s (n=100)
withQm: 5 wallclock secs ( 5.05 usr + 0.00 sys = 5.05 CPU) @
19.81/s (n=100)
withQmAnd: 5 wallclock secs ( 4.73 usr + 0.00 sys = 4.73 CPU) @
21.12/s (n=100)
(Using Perl v5.8.0 ActiveState build 805 on Win2k server)
So it seems the ?: is actually fastest ;-)
Jenda
===== [EMAIL PROTECTED] === http://Jenda.Krynicky.cz =====
When it comes to wine, women and song, wizards are allowed
to get drunk and croon as much as they like.
-- Terry Pratchett in Sourcery
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