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From "Remi Arntzen (JIRA)" <j...@apache.org>
Subject [jira] Created: (MATH-153) RandomDataImpl nextInt(int, int) nextLong(long, long)
Date Mon, 31 Jul 2006 03:50:13 GMT
RandomDataImpl nextInt(int, int) nextLong(long, long)
-----------------------------------------------------

                 Key: MATH-153
                 URL: http://issues.apache.org/jira/browse/MATH-153
             Project: Commons Math
          Issue Type: Bug
    Affects Versions: Nightly Builds, 1.1 Final
            Reporter: Remi Arntzen
            Priority: Critical


RandomDataImpl.nextInt(Integer.MIN_VALUE, Integer.MAX_VALUE) suffers from overflow errors.

change
return lower + (int) (rand.nextDouble() * (upper - lower + 1));
to
return (int) (lower + (long) (rand.nextDouble()*((long) upper - lower + 1)));

additional checks must be made for the nextlong(long, long) method.
At first I thought about using MathUtils.subAndCheck(long, long) but there is only an int
version avalible, and the problem is that subAndCheck internaly uses long values to check
for overflow just as my previous channge proposes.  The only thing I can think of is using
a BigInteger to check for the number of bits required to express the difference.

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