Andrzej Bialecki wrote:
Paul Elschot wrote:
On Saturday 28 January 2006 19:27, eks dev wrote:
might be interesting:
http://www.iis.uni-stuttgart.de/intset/
Another way to represent Bit(Integer)Set. Should
outperform nicely BitSet or HashBitSet as far as
iteration speed and memory is concern. In Lucene where
distribution of set bits is typically exponential...
usage in caching, Filter...
This gives some context, a performance comparison program,
and indicates that the licence for the context is LGPL:
http://www.iis.uni-stuttgart.de/personen/lippold/MathCollection/index-en.html
Unfortunately, the license distributed with the JAR (which we must
assume takes precedence over whatever is stated on the web pages) is
much more restrictive, it's the Java Research License, which
specifically disallows any commercial use. So, short of reimplementing
it from scratch it's of no use except for academic study. Pity.
The idea is fairly simple: If most uses of BitSet are sparse over a
large universe, then using a tree of BitSets would be cheaper.
The implementation needs an Interface representation of BitSet to work,
with BitSet being derived from that implementation. Thus the code uses
IntegerSet as the fundamental interface. This is essentially all the
methods in BitSet, with BitSet being changed to IntegerSet where ever it
occurs. BitIntegerSet is a copy of BitSet from Sun but trivially
modified to implement IntegerSet.
It is this usage of BitSet that is causing the basic problem.
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