[R] -ffloat-store

[Peter Perkins]

hi -

in the context of funny problems with optim() -- bug report 671 -- Prof
Brian Ripley  wrote:
> I think this is the usual problem with inconsistent internal precision
> on Linux compilers, so try compiling optim.c with -ffloat-store to make
> gcc IEEE-compliant.

this was new to me, but then i am somewhat new to linux and gcc.  a grep
on the R-1.1.1 source dist'n does not match -ffloat-store.  i've lately
run into funny "jumps" while using optim(), similar to what was
described in the original bug report.  according to the gcc info page,
the "extra precision" (how can that be bad?) is a hardware-specific
issue.  is there any store of R-knowledge on what hardware is affected
(i'm running on ppc -- the gcc info page mentions m68k and x86) and
what, if any, other routines might be affected?

along the same lines, is there an official R-stance on the accuracy of
libmoto for ppc?  i remember having heard some vague mention on a ppc
newsgroup about the routines in libmoto being fast but not very
accurate.  at one point, i compared results from R with libmoto to
something else and didn't find anything shocking.

thanks for any info.

- peter
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