[R-sig-Debian] Openblas?

[Göran Broström]

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? 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)

to src/Makevars, but then I got

...undefined symbol: dsytri_

when compiling.

Göran