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
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