commons-issues mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From "Dennis Hendriks (Created) (JIRA)" <j...@apache.org>
Subject [jira] [Created] (MATH-724) RandomDataImpl.nextInt does not distribute uniformly for negative lower bound
Date Mon, 12 Dec 2011 15:04:30 GMT
RandomDataImpl.nextInt does not distribute uniformly for negative lower bound
-----------------------------------------------------------------------------

                 Key: MATH-724
                 URL: https://issues.apache.org/jira/browse/MATH-724
             Project: Commons Math
          Issue Type: Bug
    Affects Versions: Nightly Builds
            Reporter: Dennis Hendriks


When using the RandomDataImpl.nextInt function to get a uniform sample in a [lower, upper]
interval, when the lower value is less than zero, the output is not uniformly distributed,
as the lowest value is practically never returned.

See the attached NextIntUniformTest.java file. It uses a [-3, 5] interval. For several values
between 0 and 1, testNextIntUniform1 prints the return value of RandomDataImpl.nextInt (as
double and as int). We see that -2 through 5 are returned several times. The -3 value however,
is only returned for 0.0, and is thus under-respresented in the integer samples. The output
of test method testNextIntUniform2 also clearly shows that value -3 is never sampled.

--
This message is automatically generated by JIRA.
If you think it was sent incorrectly, please contact your JIRA administrators: https://issues.apache.org/jira/secure/ContactAdministrators!default.jspa
For more information on JIRA, see: http://www.atlassian.com/software/jira

        

Mime
View raw message