[PATCH] Fix Bug 83237 - Values returned by std::poisson_distribution are not distributed correctly

Paolo Carlini paolo.carlini@oracle.com
Tue Dec 12 00:51:00 GMT 2017


Hi,

On 11/12/2017 23:16, Michele Pezzutti wrote:
> I lowered to N = 2500000 and still fails with a good margin.
Good. At the moment however, I think we need a bit of rationale for the 
change that you are proposing, what would you put in a comment in the 
code? It's been a while since the last time I looked into these 
algorithms, is there a simple way to explain why the change is needed 
within the basic rejection method proposed by Devroye? Devroye's book is 
freely available, have you been able to study the relevant bits already? 
(http://www.nrbook.com/devroye/). He is also very approachable in 
private email, if I remember correctly.

Eventually, we could also agree on a good way to extend the coverage of 
the testing, maybe for gcc8 simply add the testcase, but then, for gcc9 
I think we could extend it quite a bit in a consistent way, something 
like a grid from 1.0 to 50 step 1.0 with an increased N. Better if we 
figure out something that looks generic but would also have caught 
anyway 83237, if you see what I mean. I can take care of that. For the 
other discrete distributions too of course.

Thanks a lot for your help!

Paolo.



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