NetNews Usenet Archive 1992 #19/NN_1992_19.iso/spool/comp/lang/perl/5503

Text File | 1992-08-26 | 2.8 KB | 72 lines

Newsgroups: comp.lang.perl
Path: sparky!uunet!noc.near.net!meiko.com!mike
From: [e-mail] (Mike Stok)
Subject: Re: Fast String Operations?
Message-ID: <[e-mail]>
Sender: [e-mail]
Organization: Meiko Scientific Corp.
References: <[e-mail]>
Date: Wed, 26 Aug 1992 11:31:47 GMT
Lines: 60

In article <[e-mail]> [e-mail] (Randy garrett) writes:
>I'm looking for the fastest way to perform the following operation.
>Basically, this is a conversion of one database format to another.
>If I have a NULL field, indicated by 2 pipe symbols next to
>each other, I want to insert either a -1 or a ~ between the
>two pipes, depending upon whether the type of that field
>is a integer or a character.  I know the type of the field
>because I've already pre-filled that array with the correct
>types from the Data Dictionary (Thanks Sybase to Perl Interface!).
>
>So, I read in a series of lines from a file.  If I find 2 pipe
>symbols adjacent to each other, "||", in the input string, I want
>to insert either a ~  or a -1 depending on the type of that field,
>which I get from the @name array.
>
>Here's the code I'm using.  It works, but the bad news is that
>I process 800+ Megabytes of data at a crack with this. It
>takes almost a day of CPU time on a Sparc 2!  Any words of
>wisdom on how to speed it up would be greatly appreciated.

My guess at the code would be something like:

#!/usr/bin/perl

$string = "a|bcd||g||i|||";
@name = (1,2,1,1,2,1,2,1);

if ($string =~ /\|\|/)
{
  chop ($string);
  @field = split (/\|/, $string, @name);
  for ($index = 0; $index < @field; $index++)
  {
    $field[$index] = ('', '-1', '~')[$name[$index]] if $field[$index] eq '';
  }
  $string = join ('|', @field) . '|';
}

print "$string\n";

This would only do any processing if there were 2 adjacent |s in the
string, and I assume that the | is used as a field terminator rather
than a separator (hence the chop and the . '|' after the join), and
that there will always be the right number of fields in a string, and
that $[ is left at the default value of 0.  It produces a different result
to your code :-(, but if field 0 is the "a", 1 is "bcd", and field 2
is the first empty field, I see that $name[2] == 1, so this is an empty
integer field so it becomes '-1'.  My result $string was a|bcd|-1|g|~|i|~|-1|
but yours was a|bcd|~|g|-1|i|-1|~|...

I haven't measured how fast it goes compared to your code, but I would
happily buy you a beer if it's slower :-)  (I guess I should owe you one
anyway as I get a different answer)

Mike
--
The "usual disclaimers" apply.    | ... many were weak and confused, succumbing
Mike Stok                         | to drink or drugs whenever possible ...
[e-mail]                    |
Meiko tel: [phone]         |                          Hunter S. Thompson