Re^4: Replace consecutive whitespaces with single whitespace

Besides which, the extra work is negligible

Maybe, maybe not. Whether it's negligible or not depends on the data at hand. If you have a long string with many single spaces it does matter as you avoid copying the string.

our $str = "x " x 1000;

cmpthese -1, {
    single => sub {local $_ = $::str; s/\s+/ /g},
    multiple => sub {local $_ = $::str; s/\s{2,}/ /g;}
};
__END__
           Rate   single multiple
single   1969/s       --     -40%
multiple 3287/s      67%       --
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Copying the string on each single space is an inefficient algorithm.

Comment on Re^4: Replace consecutive whitespaces with single whitespace Download Code

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Re^5: Replace consecutive whitespaces with single whitespace by tilly (Archbishop) on Mar 27, 2009 at 13:20 UTC
You do not copy the string on each single space. If you did then the performance of the substitution would scale like O(n*n), which it does not. As your benchmark shows, the overhead for the operation is less than a factor of 2. This is extremely unlikely to be a make or break performance issue. There are plenty of other operations you are likely to do with the string that have an even larger overhead. (For example reading it in or printing it.) Unless performance has proven to be an issue and this is where performance was lost, I remain unconcerned.	[reply]

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Re^5: Replace consecutive whitespaces with single whitespace
by tilly (Archbishop) on Mar 27, 2009 at 13:20 UTC

not

As your benchmark shows, the overhead for the operation is less than a factor of 2. This is extremely unlikely to be a make or break performance issue. There are plenty of other operations you are likely to do with the string that have an even larger overhead. (For example reading it in or printing it.)

Unless performance has proven to be an issue and this is where performance was lost, I remain unconcerned.

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