commons-issues mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From "Phil Steitz (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (MATH-1300) BitsStreamGenerator#nextBytes(byte[]) is wrong
Date Sun, 20 Dec 2015 00:28:46 GMT

    [ https://issues.apache.org/jira/browse/MATH-1300?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15065584#comment-15065584
] 

Phil Steitz commented on MATH-1300:
-----------------------------------

I am not sure that I buy the fact that this is a bug.  We don't advertise this invariant and
I don't see the need to constrain implementations to satisfy it.  Unless I am misunderstanding,
we *do* provide seed-consistency with constant output buffer size and that is what practical
implementations should depend on.  Is there a practical use case that requires the invariant
asked for in this issue?

> BitsStreamGenerator#nextBytes(byte[]) is wrong
> ----------------------------------------------
>
>                 Key: MATH-1300
>                 URL: https://issues.apache.org/jira/browse/MATH-1300
>             Project: Commons Math
>          Issue Type: Bug
>    Affects Versions: 3.5
>            Reporter: Rostislav Krasny
>         Attachments: MersenneTwister2.java, TestMersenneTwister.java
>
>
> Sequential calls to the BitsStreamGenerator#nextBytes(byte[]) must generate the same
sequence of bytes, no matter by chunks of which size it was divided. This is also how java.util.Random#nextBytes(byte[])
works.
> When nextBytes(byte[]) is called with a bytes array of length multiple of 4 it makes
one unneeded call to next(int) method. This is wrong and produces an inconsistent behavior
of classes like MersenneTwister.
> I made a new implementation of the BitsStreamGenerator#nextBytes(byte[]) see attached
code.



--
This message was sent by Atlassian JIRA
(v6.3.4#6332)

Mime
View raw message