Bug#921193: libmkl-rt: Octave returns wrong results when large arrays are multiplied

[Ido Halperin]

Package: libmkl-rt
Version: 2019.1.144-4
Severity: important

Dear Maintainer,

After installing intel-mkl and setting MKL as default BLAS/LAPACK
implementation, wrong results are obtained when large arrays are
multiplied in octave. Here is the output of a MWE:


octave:1> x1=0:100000;[x1;x1]*[x1;x1]'
ans =

   450792059465624   472496191531028
   512874660819596   531922410008450

  
This result is absolutely wrong. All the elements in the 'ans' matrix
should have the same value. 

For example, after changing back to the original BLAS/LAPACK
implementation, the result is


octave:1> x1=0:100000;[x1;x1]*[x1;x1]'
ans =

   333338333350000   333338333350000
   333338333350000   333338333350000



which is the right one.


Regards

Ido


-- System Information:
Debian Release: buster/sid
  APT prefers testing
  APT policy: (500, 'testing'), (500, 'stable')
Architecture: amd64 (x86_64)
Foreign Architectures: i386

Kernel: Linux 4.19.0-1-amd64 (SMP w/4 CPU cores)
Locale: LANG=en_US.UTF-8, LC_CTYPE=en_US.UTF-8 (charmap=UTF-8),
LANGUAGE=en_US.UTF-8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash
Init: systemd (via /run/systemd/system)
LSM: AppArmor: enabled

Versions of packages libmkl-rt depends on:
ii  debconf [debconf-2.0]              1.5.70
ii  libatlas3-base [liblapack.so.3]    3.10.3-7+b1
ii  libblas3 [libblas.so.3]            3.8.0-2
ii  libc6                              2.28-5
ii  libgcc-5-dev                       5.4.1-4
ii  libgcc-6-dev                       6.5.0-1
ii  libgcc-7-dev                       7.4.0-2
ii  libgcc-8-dev                       8.2.0-15
ii  liblapack3 [liblapack.so.3]        3.8.0-2
ii  libmkl-locale                      2019.1.144-4
ii  libmkl-meta-computational          2019.1.144-4
ii  libmkl-meta-interface              2019.1.144-4
ii  libmkl-meta-threading              2019.1.144-4
ii  libomp-7-dev                       1:7.0.1-4
ii  libomp-dev                         1:7.0-47
ii  libopenblas-base [liblapack.so.3]  0.3.5+ds-1

libmkl-rt recommends no packages.

libmkl-rt suggests no packages.

-- debconf information:
* libmkl-rt/use-as-default-blas-lapack: true
* libmkl-rt/exact-so-3-selections: libblas.so.3, liblapack.so.3,
libblas64.so.3, liblapack64.so.3,
  libmkl-rt/title: