Re: Need hash: uthash?

[Joerg Sonnenberger <joerg@britannica.bec.de>]

On Thu, Jul 28, 2011 at 05:12:27PM +0200, Kristaps Dzonsons wrote:
> On 28/07/2011 17:04, Joerg Sonnenberger wrote:
> >On Thu, Jul 28, 2011 at 12:32:32PM +0200, Kristaps Dzonsons wrote:
> >>mandoc is getting a `tr' implementation*, needed primarily for
> >>perlpod.  This is expensive as it involves iterating over each
> >>character in each text string, then each element in an array of `tr'
> >>characters (or escape sequences).  Expect it in the next few commits
> >>(now it's in polish phase).
> >
> >Shouldn't this use a simple byte lookup table for the hot path?
> >Most of the tr processing applies to non-special sequences and unicode
> >or other \-literals are rare.
> 
> Joerg,
> 
> On the contrary.  perlpod (followed by GNU) is the main offender and
> makes significant use of escape-translation.  Yes, I could
> special-case \(*W, but really would rather not.

i think you misunderstand me. My point is that the really critical path
for .tr processing is handling non-backslashed sequences. E.g. normal
text. For that, building a byte lookup table drops the performance
penalty to a few percent at most. The rest is relative expensive anyway,
but it should be only a very small part of the input. So the O(nm) drops
down to O(normal text + m * backslash-literals).

Joerg
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