[Rd] xerbla called from BLAS routine (PR#8100)

Prof Brian Ripley ripley at stats.ox.ac.uk
Mon Aug 29 12:48:23 CEST 2005

On Mon, 29 Aug 2005, Göran Broström wrote:

> On Mon, Aug 29, 2005 at 10:27:24AM +0100, Prof Brian Ripley wrote:
>> On Mon, 29 Aug 2005, Göran Broström wrote:
> [...]
>>> BTW, the original BLAS xerbla (from the netlib page you referred to)
>>> gives the message:
>>>    WRITE( *, FMT = 9999 )SRNAME, INFO
>>> 9999 FORMAT( ' ** On entry to ', A6, ' parameter number ', I2, ' had ',
>>>    $      'an illegal value' )
>>> which I think is even better than my original suggestion.
>>> (Why was it changed?)
>> Probably because R is not a Fortran program and so needs to make clear
>> what these refer to, and because LAPACK does have other error values that
>> invalid parameter values.
> LAPACK/BLAS routines call xerbla "if an input parameter has an
> invalid value" (exact quote from  XERBLA at Netlib). Other types of errors
> are not printed (by xerbla), but it is up to the user to check the return
> value of the argument 'INFO'. See
> http://www.netlib.org/lapack/lug/node119.html.

Maybe, that is not actually true for real-life LAPACK implementations, as 
I did say.

> So we can safely give the more informative, original, error messages,
> together with mentioning LAPACK and eventually BLAS, whatever you prefer.
> This would "make clear what these refer to". Given that other BLAS/LAPACK
> routines than xerbla aren't changed in R, of course.

Irrelevant as R is often compiled against other ones implementations.

Brian D. Ripley,                  ripley at stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272866 (PA)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595

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