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Re: Using filepath method to identify an .html page

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Date Tue, 22 Jan 2013 14:00:16 -0500
From Dave Angel <d@davea.name>
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Subject Re: Using filepath method to identify an .html page
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On 01/22/2013 01:26 PM, Ferrous Cranus wrote:
>
>> <snip>
>
> sub hashit {
>     my $url=shift;
>     my @ltrs=split(//,$url);
>     my $hash = 0;
>
>     foreach my $ltr(@ltrs){
>          $hash = ( $hash + ord($ltr)) %10000;
>     }
>     printf "%s: %0.4d\n",$url,$hash
>
> }
>
>
> which yields:
> $ perl testMD5.pl
> /index.html: 1066
> /about/time.html: 1547
>

If you use that algorithm to get a 4 digit number, it'll look good for 
the first few files.  But if you try 100 files, you've got almost 40% 
chance of a collision, and if you try 10001, you've got a 100% chance.


So is it really okay to reuse the same integer for different files?

I tried to help you when you were using the md5 algorithm.  By using 
enough digits/characters, you can cut the likelihood of a collision 
quite small.  But 4 digits, don't be ridiculous.


-- 
DaveA

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Thread

Using filepath method to identify an .html page Ferrous Cranus <nikos.gr33k@gmail.com> - 2013-01-22 02:07 -0800
  Re: Using filepath method to identify an .html page Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-01-22 11:31 +0000
    Re: Using filepath method to identify an .html page Ferrous Cranus <nikos.gr33k@gmail.com> - 2013-01-22 03:53 -0800
      Re: Using filepath method to identify an .html page Chris Angelico <rosuav@gmail.com> - 2013-01-22 23:26 +1100
    Re: Using filepath method to identify an .html page Ferrous Cranus <nikos.gr33k@gmail.com> - 2013-01-22 04:02 -0800
      Re: Using filepath method to identify an .html page Lele Gaifax <lele@metapensiero.it> - 2013-01-22 13:22 +0100
      Re: Using filepath method to identify an .html page Dave Angel <d@davea.name> - 2013-01-22 07:29 -0500
        Re: Using filepath method to identify an .html page Ferrous Cranus <nikos.gr33k@gmail.com> - 2013-01-22 04:47 -0800
          Re: Using filepath method to identify an .html page Ferrous Cranus <nikos.gr33k@gmail.com> - 2013-01-22 04:50 -0800
          Re: Using filepath method to identify an .html page Chris Angelico <rosuav@gmail.com> - 2013-01-22 23:59 +1100
          Re: Using filepath method to identify an .html page Ferrous Cranus <nikos.gr33k@gmail.com> - 2013-01-22 04:50 -0800
        Re: Using filepath method to identify an .html page Ferrous Cranus <nikos.gr33k@gmail.com> - 2013-01-22 04:47 -0800
          Re: Using filepath method to identify an .html page Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-01-22 13:04 +0000
            Re: Using filepath method to identify an .html page Ferrous Cranus <nikos.gr33k@gmail.com> - 2013-01-22 05:57 -0800
              Re: Using filepath method to identify an .html page Chris Angelico <rosuav@gmail.com> - 2013-01-23 01:33 +1100
                Re: Using filepath method to identify an .html page Ferrous Cranus <nikos.gr33k@gmail.com> - 2013-01-22 06:55 -0800
                Re: Using filepath method to identify an .html page Dave Angel <d@davea.name> - 2013-01-22 10:05 -0500
                Re: Using filepath method to identify an .html page Ferrous Cranus <nikos.gr33k@gmail.com> - 2013-01-22 07:21 -0800
                Re: Using filepath method to identify an .html page Chris Angelico <rosuav@gmail.com> - 2013-01-23 02:27 +1100
                Re: Using filepath method to identify an .html page Michael Torrie <torriem@gmail.com> - 2013-01-22 11:36 -0700
                Re: Using filepath method to identify an .html page Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-01-22 23:40 +0000
                Re: Using filepath method to identify an .html page Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-01-22 23:40 +0000
                Re: Using filepath method to identify an .html page Michael Torrie <torriem@gmail.com> - 2013-01-22 17:07 -0700
                Re: Using filepath method to identify an .html page MRAB <python@mrabarnett.plus.com> - 2013-01-23 00:40 +0000
                Re: Using filepath method to identify an .html page rusi <rustompmody@gmail.com> - 2013-01-22 18:55 -0800
                Re: Using filepath method to identify an .html page Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-01-23 02:50 +0000
                Re: Using filepath method to identify an .html page rusi <rustompmody@gmail.com> - 2013-01-22 19:04 -0800
                Re: Using filepath method to identify an .html page Chris Angelico <rosuav@gmail.com> - 2013-01-23 15:44 +1100
                Re: Using filepath method to identify an .html page Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2013-01-22 22:15 -0500
                Re: Using filepath method to identify an .html page MRAB <python@mrabarnett.plus.com> - 2013-01-23 03:35 +0000
                Re: Using filepath method to identify an .html page Michael Torrie <torriem@gmail.com> - 2013-01-22 22:10 -0700
                Re: Using filepath method to identify an .html page Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2013-01-23 01:13 -0500
                RE: Using filepath method to identify an .html page "Leonard, Arah" <Arah.Leonard@bruker-axs.com> - 2013-01-23 16:33 +0000
                Re: Using filepath method to identify an .html page Ferrous Cranus <nikos.gr33k@gmail.com> - 2013-01-23 08:51 -0800
                RE: Using filepath method to identify an .html page "Leonard, Arah" <Arah.Leonard@bruker-axs.com> - 2013-01-23 18:19 +0000
                Re: Using filepath method to identify an .html page Mark Lawrence <breamoreboy@yahoo.co.uk> - 2013-01-23 18:36 +0000
                Re: Using filepath method to identify an .html page Dave Angel <d@davea.name> - 2013-01-23 17:46 -0500
                Re: Using filepath method to identify an .html page Ferrous Cranus <nikos.gr33k@gmail.com> - 2013-01-23 08:51 -0800
                Re: Using filepath method to identify an .html page Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-01-22 23:34 +0000
                Re: Using filepath method to identify an .html page Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-01-22 23:35 +0000
                Re: Using filepath method to identify an .html page Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-01-22 23:34 +0000
                Re: Using filepath method to identify an .html page Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-01-22 23:36 +0000
                Re: Using filepath method to identify an .html page Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-01-22 23:36 +0000
                Re: Using filepath method to identify an .html page Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-01-22 23:37 +0000
                Re: Using filepath method to identify an .html page Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-01-22 23:39 +0000
                Re: Using filepath method to identify an .html page Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-01-22 23:38 +0000
                Re: Using filepath method to identify an .html page Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-01-22 23:39 +0000
                Re: Using filepath method to identify an .html page Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-01-22 23:37 +0000
                Re: Using filepath method to identify an .html page Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-01-22 23:38 +0000
                Re: Using filepath method to identify an .html page Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-01-22 23:39 +0000
                Re: Using filepath method to identify an .html page Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-01-22 23:36 +0000
                Re: Using filepath method to identify an .html page Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-01-22 23:35 +0000
                Re: Using filepath method to identify an .html page Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-01-22 23:37 +0000
                Re: Using filepath method to identify an .html page Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2013-01-22 16:44 -0500
                Re: Using filepath method to identify an .html page Ferrous Cranus <nikos.gr33k@gmail.com> - 2013-01-22 07:21 -0800
                Re: Using filepath method to identify an .html page Chris Angelico <rosuav@gmail.com> - 2013-01-23 02:07 +1100
                Re: Using filepath method to identify an .html page Peter Otten <__peter__@web.de> - 2013-01-22 16:25 +0100
                Re: Using filepath method to identify an .html page Ferrous Cranus <nikos.gr33k@gmail.com> - 2013-01-22 07:46 -0800
                Re: Using filepath method to identify an .html page Dave Angel <d@davea.name> - 2013-01-22 11:11 -0500
                RE: Using filepath method to identify an .html page "Leonard, Arah" <Arah.Leonard@bruker-axs.com> - 2013-01-22 16:23 +0000
                Re: Using filepath method to identify an .html page Ferrous Cranus <nikos.gr33k@gmail.com> - 2013-01-22 10:13 -0800
                Re: Using filepath method to identify an .html page Michael Torrie <torriem@gmail.com> - 2013-01-22 11:43 -0700
                Re: Using filepath method to identify an .html page Ferrous Cranus <nikos.gr33k@gmail.com> - 2013-01-22 10:13 -0800
                Re: Using filepath method to identify an .html page Ferrous Cranus <nikos.gr33k@gmail.com> - 2013-01-22 07:46 -0800
                Re: Using filepath method to identify an .html page Ferrous Cranus <nikos.gr33k@gmail.com> - 2013-01-22 07:59 -0800
                Re: Using filepath method to identify an .html page Chris Angelico <rosuav@gmail.com> - 2013-01-23 03:11 +1100
                Re: Using filepath method to identify an .html page Ferrous Cranus <nikos.gr33k@gmail.com> - 2013-01-22 10:26 -0800
                Re: Using filepath method to identify an .html page MRAB <python@mrabarnett.plus.com> - 2013-01-22 18:49 +0000
                Re: Using filepath method to identify an .html page Michael Torrie <torriem@gmail.com> - 2013-01-22 11:49 -0700
                Re: Using filepath method to identify an .html page Dave Angel <d@davea.name> - 2013-01-22 14:00 -0500
                Re: Using filepath method to identify an .html page Peter Otten <__peter__@web.de> - 2013-01-22 20:16 +0100
                Re: Using filepath method to identify an .html page Ferrous Cranus <nikos.gr33k@gmail.com> - 2013-01-22 23:25 -0800
                Re: Using filepath method to identify an .html page Michael Torrie <torriem@gmail.com> - 2013-01-23 08:25 -0700
                Re: Using filepath method to identify an .html page Ferrous Cranus <nikos.gr33k@gmail.com> - 2013-01-23 07:56 -0800
                Re: Using filepath method to identify an .html page Ferrous Cranus <nikos.gr33k@gmail.com> - 2013-01-23 07:56 -0800
                Re: Using filepath method to identify an .html page Ferrous Cranus <nikos.gr33k@gmail.com> - 2013-01-22 23:25 -0800
                Re: Using filepath method to identify an .html page Ferrous Cranus <nikos.gr33k@gmail.com> - 2013-01-22 10:26 -0800
                Re: Using filepath method to identify an .html page Ferrous Cranus <nikos.gr33k@gmail.com> - 2013-01-22 07:59 -0800
                Re: Using filepath method to identify an .html page John Gordon <gordon@panix.com> - 2013-01-22 16:55 +0000
                Re: Using filepath method to identify an .html page Ferrous Cranus <nikos.gr33k@gmail.com> - 2013-01-22 10:07 -0800
                Re: Using filepath method to identify an .html page John Gordon <gordon@panix.com> - 2013-01-22 18:37 +0000
                Re: Using filepath method to identify an .html page Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2013-01-22 17:01 -0500
                Re: Using filepath method to identify an .html page Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-01-22 23:23 +0000
                Re: Using filepath method to identify an .html page rusi <rustompmody@gmail.com> - 2013-01-22 09:33 -0800
                Re: Using filepath method to identify an .html page Mark Lawrence <breamoreboy@yahoo.co.uk> - 2013-01-22 17:54 +0000
                Re: Using filepath method to identify an .html page Ferrous Cranus <nikos.gr33k@gmail.com> - 2013-01-22 10:23 -0800
                Re: Using filepath method to identify an .html page Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-01-22 22:45 +0000
                Re: Using filepath method to identify an .html page Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-01-22 22:44 +0000
                Re: Using filepath method to identify an .html page Mitya Sirenef <msirenef@lightbird.net> - 2013-01-22 19:23 -0500
                Re: Using filepath method to identify an .html page Ferrous Cranus <nikos.gr33k@gmail.com> - 2013-01-22 06:55 -0800
  Re: Using filepath method to identify an .html page Michael Torrie <torriem@gmail.com> - 2013-01-22 11:21 -0700
  Re: Using filepath method to identify an .html page alex23 <wuwei23@gmail.com> - 2013-01-22 17:27 -0800

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