[Rd] Two bugs showing up mostly on SPARC systems

Radford Neal radford at cs.toronto.edu
Wed Jul 15 03:29:36 CEST 2015

On Tue, Jul 14, 2015 at 07:52:56PM -0400, Duncan Murdoch wrote:
> On 14/07/2015 6:08 PM, Radford Neal wrote:
> > In testing pqR on Solaris SPARC systems, I have found two bugs that
> > are also present in recent R Core versions.  You can see the bugs and
> > fixes at the following URLs:
> > 
> >   https://github.com/radfordneal/pqR/commit/739a4960a4d8f3a3b20cfc311518369576689f37
> Thanks for the report.  Just one followup on this one:
> There are two sections of code that are really similar.  Your patch
> applies to the code in port_nlsb(), but there's a very similar test in
> port_nlminb(), which is called from nlminb() in R.  Do you think it
> would be a good idea to apply the same patch there as well?  It doesn't
> look like it would hurt, but I don't know this code at all, so it might
> be unnecessary.

Looking at nlminb, it seems that this bug doesn't exist there.  The 
R code sets low <- upp <- NULL, as in nls, but later there is an 
"else low <- upp <- numeric()" that ensures that low and upp are never
actually NULL.  This may have been a fix for the bug showing up in
nlminb that was not applied to nls as well (and of course, the fix
didn't delete the now pointless low <- upp <- NULL).

The nlminb code might be a better fix, stylistically, after removing
"low <- upp <- NULL", though it seems that both it and my fix for nls
should work.  Of course, both assume that the call of the C function
is done only from this R code, so no other types for low and upp are
possible.  And really the whole thing ought to be rewritten, since the
.Call functions modify variables without any regard for whether or not
their values are shared.

   Radford Neal

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