[Octave-bug-tracker] [bug #58905] "Non-real pivot encountered" during make check for ichol

[anonymous]

Follow-up Comment #4, bug #58905 (project octave):

With gcc 11.0.0 20200806 (experimental) (the git source), the error still
exists.

I managed to reproduce the error with Clang. I moved the tests in ichol.m to a
standalone file (tst_ichol.m attached). If I use the run_octave script from
the build directory for Clang, I don't get an error but if I install it
system-wide and then run it, I get assertion failures in tst_ichol.m like
this:


error: ASSERT errors for:  assert (norm (A2 - L * L', "fro") / norm (A2,
"fro"),0.0893,1e-4)

  Location  |  Observed  |  Expected  |  Reason
     ()        0.088946      0.0893      Abs err 0.00035448 exceeds tol 0.0001
by 0.0003


With both clang and gcc, the error goes away when using "-march=x86-64" and
comes back for "-march=native" or "-march=znver2". Those build flags only
apply to Octave not to SuiteSparse, which is pre-built from the distro
repository.

In addition to Octave, the system-wide SuiteSparse library is also used by
Julia. (My Julia install is a pre-built binary, not built from source). I
tried the routines here [1] but since I don't have Matlab, and Julia seems to
outsource ichol to Matlab, the test of whether Julia gets the same error is
inconclusive.

I'm OK with calling this bug Works For Me if I'm the only one with the error
(Zen 2, SuiteSparse versions 5.7.0 to 5.8.1, OpenBLAS 0.3.7 to 0.3.10, gcc 9.0
to gcc 10.1, clang 9.0 to 10.0).

[1] http://danspielman.github.io/Laplacians.jl/v0.1/usingSolvers/index.html

(file #49640)
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Additional Item Attachment:

File name: tst_ichol.m                    Size:3 KB
    <https://file.savannah.gnu.org/file/tst_ichol.m?file_id=49640>



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