[R-sig-Debian] Openblas?

[Göran Broström]

On 2020-07-15 14:36, Dirk Eddelbuettel wrote:
> 
> Göran,
> 
> This is not an easy email to reply to because it _contains nothing
> reproducible_.

Thanks Dirk,

Sorry about that, but my real question was (see below): "Is the problem 
that openblas uses C versions of blas?" That is, do I need to change

F77_CALL(name)(...);

to

cblas_name(...);

everywhere? And if so, is this really a good idea with old code?

I'll try to extract a reproducible example from the package (eha) where 
I run it.

Göran

> 
> On 15 July 2020 at 13:24, Göran Broström wrote:
> | Hello,
> |
> | I thought that I should try openblas when building a CRAN package
> | containing lots of old (twentieth century) C-code with frequent calls to
> | blas and lapack routines. I have the following options on my Ubuntu
> | 20.04 machine:
> |
> |     Selection    Path                           Priority   Status
> | ------------------------------------------------------------
> | * 0            openblas-pthread/libblas.so.3   100      auto mode
> |    1            blas/libblas.so.3               10      manual mode
> |    2            openblas-openmp/libblas.so.3    95      manual mode
> |    3            openblas-pthread/libblas.so.3   100     manual mode
> |
> | I tried all four alternatives by timing one particular function call and
> | got quite surprising (to me) results:
> |
> | Selection        user   system elapsed
> | 0               3.279    1.839   1.900
> | 1               0.899    0.052   0.953
> | 2             158.948    3.661  20.915
> | 3               3.277    1.894   1.908
> |
> | Comments on that?
> 
> How could I comment?  I do not know what code you ran.
> 
> | To me it seems clear that openblas (0, 2, 3) has
> | nothing to offer me, as my C code stands now. Is the problem that
> | openblas uses C versions of blas? I am using the Fortran version via
> |
> | F77_CALL(name)
> |
> | I tried adding
> |
> | PKG_CFLAGS = $(SHLIB_OPENMP_CFLAGS)
> | PKG_LIBS = $(SHLIB_OPENMP_CFLAGS)
> 
> This is missing LAPACK and BLAS so ...
> |
> | to src/Makevars, but then I got
> |
> | ...undefined symbol: dsytri_
> 
> ... so get a _linker error_ about missing symbols.
>   
> | when compiling.
> 
> You meant linking, not compiling.
> 
> Dirk
>