[R] fitting in logistic model

[Marc Schwartz]

<Snippage>

On Jun 30, 2009, at 2:12 PM, Marc Schwartz wrote:
>
> Well....barring a correction from someone with more low level  
> insight, I would tend to suspect that the difference in our findings  
> may be attributed to some interaction of hardware, OS, compiler and  
> BLAS, perhaps weighted more to the latter two. When I build from  
> source, I do use the Apple vecLib BLAS (the default), as opposed to  
> the R BLAS.
>
> To distill this down to the key issue, all else being equal  
> (within .Machine$double.eps), I suspect that this leads us back to  
> rounding as being the source of Fabrizio's observations.


FWIW, I re-built R here so that it would use the R provided BLAS and  
LAPACK rather than the Apple provided versions.

Bottom line, no difference in my results here. So there is something  
more subtle going on here relative to either rounding and/or perhaps  
precision, which may now point less to the BLAS/LAPACK combination and  
perhaps more to other compiler optimizations or OS issues.

Perhaps a member of R Core could offer some insights?

Thanks,

Marc