Hi Jenda,
That was amazing..... It was a good learning for me, and I never knew
about Benchmark...
Sorry for that...
My reasoning was absolutely logical and nothing systematical....
Thanks for the great reasoning which was real real systematical.
But the same script in my environment gives me the following result:
Benchmark: timing 100 iterations of withAry, withAryAnd, withIf,
withIfAnd, withQm, withQmAnd...
withAry: 18 wallclock secs (17.60 usr + 0.01 sys = 17.61 CPU) @
5.68/s (n=100)
withAryAnd: 17 wallclock secs (17.37 usr + 0.01 sys = 17.38 CPU) @
5.75/s (n=100)
withIf: 20 wallclock secs (19.34 usr + 0.00 sys = 19.34 CPU) @
5.17/s (n=100)
withIfAnd: 19 wallclock secs (19.07 usr + 0.00 sys = 19.07 CPU) @
5.24/s (n=100)
withQm: 16 wallclock secs (16.42 usr + 0.01 sys = 16.43 CPU) @
6.09/s (n=100)
withQmAnd: 17 wallclock secs (16.10 usr + 0.00 sys = 16.10 CPU) @
6.21/s (n=100)
Well..... This is HP-UX 9000/785.........
Now I really wonder how consistent the Benchmark gives the result
properly..... bcoz different runs gave different results...
Fine anyhow I should admit that using array is slower than (or as fast
as) using ?:, but it is faster than using "if...else" both in your
environment and in mine (even for several runs).
Anyways thanks for letting me know a good Perl Module.... Benchmark.pm
With Best regards,
R. Kamal Raj Guptha.
-----Original Message-----
From: Jenda Krynicky [mailto:[EMAIL PROTECTED]
Sent: Tuesday, August 03, 2004 8:00 PM
To: R. Kamal Raj Guptha (WT01 - TELECOM & INTER-NETWORKING SOLUTIONS);
[EMAIL PROTECTED]
Subject: RE: Determining Odd and Even Numbers
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 =====
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