[R-sig-Fedora] R with external BLAS fails regression test

[Martyn Plummer]

Dear Tom,

The change in the Fedora RPM from using R's internal BLAS to external
BLAS means the Fedora R binary now fails one of R's regression tests,
specifically: tests/reg-BLAS.R. You can run this code by hand to verify
the issue.

As noted in the R administration and Installation Manual, "R relies on
ISO/IEC 60559 compliance of an external BLAS. This can be broken if for
example the code assumes that terms with a zero factor are always zero
and do not need to be computed - whereas x*0 can be NaN. This is checked
in the test suite."

The version of BLAS that comes with R contains patched versions of
DGBMV, DGEMM, and DGEMV.  The patch has been in place since 2010.
Presumably R blas and reference BLAS have been divergent ever since.

I guess this should be reported upstream as a BLAS bug. Recalling the
previous thread on openblas, I note that openblas does pass the
regression test.

Martyn

CC: Lejeczek, who reported the bug, and R-SIG-Fedora for information.
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