[Rd] [R] Building with MKL on Ubuntu

[Peter Dalgaard]

Anand Patil wrote:
> On Wed, Nov 5, 2008 at 5:59 PM, Martyn Plummer <plummer at iarc.fr> wrote:
> 
>> It looks like the em64t version of MKL fails the test for the accuracy
>> of zdotu ("checking whether double complex BLAS can be used") and is
>> therefore dropped in favour of R's built-in BLAS.  I have just tested
>> this on Fedora and get the same result.
>>
>> The 32-bit MKL does work for me.
>>
>> Martyn
>>
> 
> Many thanks, Martyn. The 64-bit index space is important to me, will I lose
> it if I link against the 32-bit MKL? Also, should I file a bug report with
> Intel?
> Anand

There's also the option of "breaking the thermometer". You might examine
that check and decide whether the loss of accuracy is enough for you to
worry about and if not, take out the test from configure.

Apparently, this check was put in place in R-2.2.0

    o Any external BLAS found is now tested to see if the complex
        routine zdotu works correctly: this provides a compatibility
        test of compiler return conventions.

which suggests that the expected failure is catastrophic, and looking at
the code, there's a fuzz of 1e-10 which would seem to be about 1e5 times
larger than required.

-- 
   O__  ---- Peter Dalgaard             Øster Farimagsgade 5, Entr.B
  c/ /'_ --- Dept. of Biostatistics     PO Box 2099, 1014 Cph. K
 (*) \(*) -- University of Copenhagen   Denmark      Ph:  (+45) 35327918
~~~~~~~~~~ - (p.dalgaard at biostat.ku.dk)              FAX: (+45) 35327907