Henry, you are right.
binSearch() is slow because the indexing, as in:
for $mid in ($pStart + $pEnd) idiv 2,
$sVal in $pSeq[$mid]
is not O(1) as it is in a true array. Depending on the particular XSLT
processor, this may be even O(N), thus giving a dismal O(N^2) for the
complete search.
I tried to compare a key-based search with your linear search and when
searching in 1000 words the key-based search seems to be about twice
faster on the average (when the strings are in the middle of the
sequence).
Therefore, when searching only in a smal sequence of strings, the
linear search isn't bad at all.
Cheers,
Dimitre
On Wed, Mar 2, 2011 at 3:33 PM, Henry S. Thompson
<ht(_at_)inf(_dot_)ed(_dot_)ac(_dot_)uk> wrote:
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Dimitre Novatchev writes:
One way is to have the strings sorted. Then use binary search -- this
is O(log(N)).
Maybe that will have an advantage for much bigger sets, but for my
test case it was considerably slower -- 18ms net vs. 9ms net for the
(some $s . . . satisfies) and $w=$stops versions, and 2ms net for the
best (key-based) one.
I'd be very interested if you could compare binSearch with the
key-based version I sent on your large dictionary example. . .
ht
- --
Henry S. Thompson, School of Informatics, University of Edinburgh
10 Crichton Street, Edinburgh EH8 9AB, SCOTLAND -- (44) 131 650-4440
Fax: (44) 131 651-1426, e-mail:
ht(_at_)inf(_dot_)ed(_dot_)ac(_dot_)uk
URL: http://www.ltg.ed.ac.uk/~ht/
[mail from me _always_ has a .sig like this -- mail without it is forged
spam]
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Cheers,
Dimitre Novatchev
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