Message-ID: <19990113225414.A21869@sirio.stat.unipd.it>
Date: 1999-01-13T21:54:14Z
From: Guido Masarotto
Subject: a bug and a question
In-Reply-To: <x2aezn5viz.fsf@blueberry.kubism.ku.dk>; from Peter Dalgaard BSA on Wed, Jan 13, 1999 at 11:15:00AM +0100
On Wed, Jan 13, 1999 at 11:15:00AM +0100, Peter Dalgaard BSA wrote:
> Jim Lindsey <jlindsey at alpha.luc.ac.be> writes:
>
> > The question: I am getting various reports that R under MS-Windows and
> > X-Windows/Linux on the same machine behaves very differently for nlm
> > convergence in my libraries. Under Linux, convergence is easy with
> > many starting values, but under MS they have to be very close to the
> > MLE. Does anyone have experience with this and or an explanation?
> > Is the math used different in the two systems?
> > Jim
>
> Not entirely unlikely. The FPU should be the same of course, but the C
> and math libraries link to a Microsoft DLL, which I have heard people
> speak badly about before.
>
> Particularly the IEEE exception handling could be causing trouble if
> an iterative method wanders near the boundary of a functions domain.
> That is pure speculation, though, I suppose Guido and Brian will know
> more.
I think Peter points to the origin of the problem.
Consider that under MSWindows: (i) the source is the Unix one
(at least for the computational part);
(ii) the compiler is one that many of us are using under Unix
(egcs 1.1); (iii) the assembler is more or less the same used
under Linux (or other ix386/Unix) BUT the libc and libm
are completly different.
Anyway, I would like to get a couple of examples to play with.
g.
(ps) I have just tested Machine()$double.rounding, but is
equal to 5 at least on my son's Win95 machine (the one
from which I am connected in this moment) and, at least in this
moment.
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