On Tue, Dec 18, 2012 at 12:51 PM, Erik Rijkers
<er@xs4all.nl> wrote:
On Tue, December 18, 2012 09:45, Alexander Korotkov wrote:
>
> You should use {0,n} to express from 0 to n occurences.
>
Thanks, but I know that of course. It's a testing program; and in the end robustness with
unexpected or even wrong input is as important as performance. (to put it bluntly, I am also
trying to get your patch to fall over ;-))
I found most of regressions in 0.9 version to be in {,n} cases. New version of patch use more of trigrams than previous versions.
For example for regex 'x[aeiou]{,2}q'.
In 0.7 version we use trigrams '__2', '_2_' and '__q'.
In 0.9 version we use trigrams 'xa_', 'xe_', 'xi_', 'xo_', 'xu_', '__2', '_2_' and '__q'.
But, actually trigram '__2' or '_2_' never occurs. It enough to have one of them, all others are just causing a slowdown. Simultaneously, we can't decide reasonably which trigrams to use without knowing their frequencies. For example, if trigrams 'xa_', 'xe_', 'xi_', 'xo_', 'xu_' were altogether more rare than '__2', newer version of patch would be faster.
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With best regards,
Alexander Korotkov.
