From murdoch@stats.uwo.ca  Wed Dec  4 20:56:03 2002
From: murdoch@stats.uwo.ca (Duncan Murdoch)
Date: Wed Dec  4 20:56:03 2002
Subject: [Rd] can this happen?
In-Reply-To: <Pine.A41.4.44.0212040841570.81760-100000@homer37.u.washington.edu>
References: <Pine.A41.4.44.0212040841570.81760-100000@homer37.u.washington.edu>
Message-ID: <dnmsuuomd8cucj79u1vi4h8bb5i4nj03ap@4ax.com>

On Wed, 4 Dec 2002 08:59:17 -0800 (PST), you wrote in message
<Pine.A41.4.44.0212040841570.81760-100000@homer37.u.washington.edu>:

>
>This is basically a question about where to start looking for a problem.
>
>I have a program that gives slightly different results on two Windows
>computers.   It is a reasonably complicated numerical optimisation, with
>iterative calls to optim().
>
>The two computers both run Windows 2000. On each computer I get the same
>results in two different versions of R (1.5.1 and 1.6.0 on one, 1.5.1 and
>1.6.1 on the other, the standard binaries), and the results are stable
>from run to run on each machine. There's nothing lurking in the workspace.

I've recently been trying to track down problems with a couple of
DLLs, and have turned up Windows bugs where common dialogs (file open,
etc) reduce the floating point precision.  The current development
version has code to fix these (everywhere I could think to put it),
but that's not in 1.6.1. 

I'll be putting these changes into 1.6.2 as well, but it's not in
r-patched yet (since I didn't know there was going to be a 1.6.2).

So if you're set up to do a Windows build, you could try compiling
r-devel, and should get consistent results (hopefully matching at
least one of the results you've seen!)

Duncan



[Rd] can this happen?
Duncan Murdoch