Re: Using Enumerated Types as Array Indexes

From:
Robert Klemme <shortcutter@googlemail.com>
Newsgroups:
comp.lang.java.programmer
Date:
Sat, 20 Aug 2011 00:20:02 +0200
Message-ID:
<9b85ssF8vsU1@mid.individual.net>
On 19.08.2011 22:05, Andreas Leitgeb wrote:

Robert Klemme<shortcutter@googlemail.com> wrote:

All solutions to fix remainder into modulo but keep the wrap around
which have been proposed so far share a common disadvantage: if the
number range is not a multiple of the divisor the value distribution
will not be uniform.

The solution I used to fix this employed a do while loop and
compareAndSet() to reset the value to the beginning of the range (0 in
this case) in a thread safe manner.


There's a much simpler "meta-way" to fix it: just stick to powers of
2 for the array length - then the overflow *does* always happen at a
multiple of the divisor and the value distribution uniform :-)


I reckon you do not mean that suggestion serious. Just in case:
limiting to powers of 2 was not an option here. And if it was, I would
not have used modulo or AtomicInteger's features but just used binary &
to cut off leading bits.

Kind regards

    robert

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