[Rd] boneheaded BLAS questions

[Ben Bolker]

   Thanks.  I know it's supposed to Just Work (and I definitely 
appreciate all the work that's gone into making it Just Work 99% of the 
time!).

   I tried --with-lapack, no joy.
   Will try to decipher the rules file tomorrow ...

   cheers
    Ben


On 3/17/21 10:25 PM, Dirk Eddelbuettel wrote:
> 
> Ben,
> 
> This stuff has worked unchanged since the 1990s when we had a _really_ far
> sighted fellow in Debian come up with the 'switch the links' scheme which was
> (and is) subsequently deployed by many numerical applications within Debian,
> R and e.g. Octave included.
> 
> And I used this ability to switch over a decade ago in a never-quite-finished
> paper which resulted in a package as well as a vignette as paper draft on
> CRAN: gcbd [1] It used the ability to switch between implementation to time
> and compare and benchmark the various BLAS and LAPACK libraries -- which was
> then motivated by a comparison with GPUs. (The actual code / package is
> stale-ish as some of the underlying packages have gone as eg the GPU one --
> but the mechanics you are after still work the exact same way on Debian and
> derivarives including Ubuntu and PopOS.)
> 
> (As a complete aside, the state of the art here is now one level up in
> libraries based on flame/blis (a riff on blas) which can do a similar logical
> switch _at runtime_ (rather than by flipping softlinks and restarting the
> app). Julia and some other languages uses that, I think Fedora may have it in
> its R build as well. Inaki may know more...)
> 
> That said, from the top of my head, I think you error may just be with the
> second R compilation -- I always (i.e. for the Debian package) use both
>    --with-blas --with-lapack
> and not just --with-blas. And I do there is public: if you know where to look
> you can see the exact invocation of the Debian build of the R package (which
> Ubuntu and Pop and ... then shadow) [2]
> 
> Hth, Dirk
> 
> [1] https://cran.r-project.org/package=gcbd
> [2] https://sources.debian.org/src/r-base/4.0.4-1/debian/rules/
>      (and I apologise for how messy this still is)
>