^ operation much slower in R 1.7.1 than in R 1.7.0 ???

Thomas Lumley <tlumley@u.washington.edu> writes:

On Tue, 5 Aug 2003, Philippe Grosjean wrote:

OK. But I was wondering if people at R-core team, especially those who
worked on Windows specific aspects, would have in mind some changes they did
between 1.7.0 and 1.7.1 than can cause this. Since these changes are mainly
corrections of bugs, the list is hopefully not so long... and it could help
a lot to have these hints. Thanks very much.

I checked that the slowdown really was happening in "^", which is
Primitive and so fairly direct.  I couldn't find anything remotely
plausible as a cause, though.

My first guess was something involving the methods package and my second
was a compiler change, so I'm 0-2 so far.

I think we can be fairly sure that the reason is that a new pow()
function was injected in the mingw runtime. You can find the actual
code in

http://cvs.sourceforge.net/cgi-bin/viewcvs.cgi/mingw/runtime/mingwex/math/

*why* this code was inserted is anyones guess. Googling threw up some
 hint that the MS-supplied pow() was upsetting strtod and causing a
 regression test failure with the Gimp. The code looks considerably
 different from the kind of stuff used on Linux though, e.g. it
 appears not to use FPU transcendentals. I suppose one could ask the
 author...

Also, R is generally compiled with -D NO_MATH_INLINES because of some
ancient messup with glibc. I'm not sure whether that is actually still
necessary, but it is forcing the use of the non-inlined pow() function.

O__  ---- Peter Dalgaard             Blegdamsvej 3  
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