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From "Rostislav Krasny (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (MATH-1307) Create a base class for all RNGs
Date Mon, 28 Dec 2015 19:12:49 GMT

    [ https://issues.apache.org/jira/browse/MATH-1307?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15073034#comment-15073034
] 

Rostislav Krasny commented on MATH-1307:
----------------------------------------

One comment about this code in the attached java file:
{code:java}    /** {@inheritDoc} */
    @Override
    public boolean nextBoolean() {
        return (nextInt() >>> 31) != 0;
    }{code}

I think {{(nextInt() >>> 31) != 0}} is better to be changed to {{(nextInt() &
1) == 1}}, i.e. instead of checking the most significant bit (sign bit) to check the least
significant bit (parity bit). It's simpler and less likely to get unevenness in results because
of some characteristic of the algorithm used in particular nextInt() implementation.

> Create a base class for all RNGs
> --------------------------------
>
>                 Key: MATH-1307
>                 URL: https://issues.apache.org/jira/browse/MATH-1307
>             Project: Commons Math
>          Issue Type: Improvement
>            Reporter: Gilles
>            Assignee: Gilles
>            Priority: Minor
>              Labels: api, inheritance
>             Fix For: 4.0
>
>         Attachments: BaseRandomGenerator.java
>
>
> I proposed to create a base class which the existing abstract classes {{AbstractRandomGenerator}}
and {{BitsStreamGenerator}} will extend.
> This would allow to define {{nextBytes(byte[])}} at the base class level.
> The code for that method is almost identical in the two hierarchies: they only differ
in a call to either {{nextInt()}} or {{next(32)}} respectively; the latter is however the
same as the former, in disguise, and is not subject to change given the type of return value.
> As a corollary, the new base class can be the unique place where to add utilities such
as the one proposed in MATH-1306.
> *Update:* {{AbstractRandomGenerator}} and {{BitsStreamGenerator}} are both obsoleted
by the class proposed in this report.



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