[Rd] NA %*% 0 == 0 (PR#4582)

[Uwe Ligges]

Prof Brian D Ripley wrote:
> non-complex %*% is fundamentally done via a call to dgemm, so the answer is
> going to depend on the BLAS library in use.  When Doug Bates introduced
> that version of matprod, we did discuss a bit the potential problems of
> cases like this.
> 
> I've cross-checked, and that _is_ what is going on with my Linux box: try
> tracing around the call to dgemm in matprod in array.c.
> 
> Brian

You are right!
Indeed, I used the ATLAS (Athlon) optimized Rblas.dll (that one you 
provide on CRAN) for R-1.8.0 and R's default Rblas.dll under R-1.7.1.
Using the other version of Rblas.dll changes the outcomes.

So I get "0" for default Rblas.dll, and NA for the Athlon optimzed one.

Uwe Ligges


> On Wed, 15 Oct 2003, Duncan Murdoch wrote:
> 
> 
>>On Wed, 15 Oct 2003 09:06:39 +0200 (MET DST), you wrote:
>>
>>
>>
>>>R-1.8.0: Does not happen for me on WindowsNT4.0 either (self compiled
>>>binary, gcc-3.3.1).
>>>
>>>
>>>
>>>>Does for me (RedHat, R 1.8.0 and 1.7.0).
>>>
>>>
>>>I guess the problem is compiler-dependend, because I get that "0" in a
>>>self-compiled R-1.7.1 (has been compiled with gcc-3.2.?).
>>>
>>>Is your binary self-compiled or from CRAN (Duncan Murdoch compiled the
>>>CRAN binary with gcc-3.3.1 as well, AFAIK)?
>>
>>I get it in Win XP with both 1.8.0 (compiled with 3.3.1) and 1.7.1
>>(compiled with 3.2.x).  I'd guess one of two things:
>>
>> - it depends on the runtime library.  (Windows versions use MSVCRT,
>>but the exact version used depends on the system you're running on.)
>>This doesn't seem to explain what happens on Linux, does it?
>>
>> - it depends on some uninitialized variable.  do_matprod is
>>surprisingly complicated, so I can't tell if this is what's happening.
>>For some reason Insight won't debug that function properly.
> 
>