Re: [Boost-bugs] [Boost C++ Libraries] #6057: Lazy variance in accumulator gives wrong result when too high statistics

Subject: Re: [Boost-bugs] [Boost C++ Libraries] #6057: Lazy variance in accumulator gives wrong result when too high statistics
From: Boost C++ Libraries (noreply_at_[hidden])
Date: 2012-11-16 07:01:29

#6057: Lazy variance in accumulator gives wrong result when too high statistics
----------------------------------------------+-----------------------------
  Reporter:  Johan <johan.luisier@…>          |       Owner:  troyer                   
      Type:  Bugs                             |      Status:  closed                   
 Milestone:  To Be Determined                 |   Component:  accumulator              
   Version:  Boost 1.44.0                     |    Severity:  Problem                  
Resolution:  worksforme                       |    Keywords:  accumulator lazy_variance
----------------------------------------------+-----------------------------

Comment (by Johan <johan.luisier@…>):

 Well, thank you for having a look. However I have to disagree. I did the
 test again this morning, with this little change made to the given source
 code:

 {{{
 unsigned i, total( 0xFFFF1 );
 }}}

 and the result is:
 {{{
 Test using 1048561 data points.

 Lazy variance accumulator : 0.00 s

 Mean : -0.436519
 Variance : 1369.89

 Immediate variance accumulator : 0.02 s

 Mean : -0.436519
 Variance : 5465.95

 Simple classe : 0.01 s

 Mean : -0.436519
 Variance : 5465.95
 }}}

 Test performed on Mandriva 2011 64 bits using gcc 4.6.1 and boost 1.46.1.

-- 
Ticket URL: <https://svn.boost.org/trac/boost/ticket/6057#comment:3>
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