Em 2013-01-02 16:53, Nicolai Scheer escreveu:
I might have chosen the wrong tool for what I'm trying to achieve in
the
first place, but can anyone comment on the algorithmic complexity of
strtr?
This is definitely not the expected behaviour for such small inputs.
Since
the inputs varied and the keys where determined automatically in my
original script, I was confronted with runtimes of several hours
compared
to just a few seconds with str_replace.
If this is the expected behaviour, at least the documentation should
be
adjusted to state that this function is very inefficient with
keylengths
that are very distant from each other...
Please open a bug to track this.
The algorithm behaves very poorly in this case because at each position
of the text, all the substrings starting there and with size between m
and n (where m is the size of the smallest pattern and n is the largest)
are checked, even if there are only two patterns with size m and n. We
could fix this easily by building a set of the pattern sizes found and
try only with those. The hashing of the substrings could also be
improved; we don't have to recalculate everything when we advance in the
text.
--
Gustavo Lopes
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