Bug#898941: caffe-cpu: Very different results for gpu and cpu calculations due to possibly problematic BLAS dependency

[Lumin]

Hi Christoph,

Thank you for this bug report. I'll take a look into it.

Sébastien, I found no code in caffe that is specific to any BLAS
implementation. Do you have any idea about the reported result variation
between netlib blas and openblas? Or do they have different level of
numerical stability assurance?

> Package: caffe-cpu
> Severity: important
> 
> Dear Maintainer,
> 
> I'm getting very different results in cpu mode compared to gpu mode, when using the libblas3 (version 3.7.0-2) package. 
> After installing the libopenblas-base package (version 0.2.19-3) the problems disappeared. I don't know whether
> this is a dependency problem of the package or it is a known problem in libblas3. I was able to uninstall and install
> libopenblas-base while libblas3 was still being installed, which is a little bit confusing to me.
> 
> Note that I reported the bug initially here: https://github.com/twhui/MSG-Net/issues/2
> 
> Note also that this bug has been found with a recompiled package with matlab support enabled. I used this howto
> https://github.com/BVLC/caffe/blob/master/docs/install_apt_debian.md, and changed only the matlab options. However, 
> I don't think that the behaviour is visible in matlab only, though I didn't try this.
> 
> Kind Regards
> Christoph
> 
> -- System Information:
> Debian Release: 9.4
>   APT prefers stable
>   APT policy: (1000, 'stable'), (900, 'stable'), (500, 'stable-updates')
> Architecture: amd64 (x86_64)
> Foreign Architectures: i386
> 
> Kernel: Linux 4.9.0-6-amd64 (SMP w/8 CPU cores)
> Locale: LANG=de_DE.UTF-8, LC_CTYPE=de_DE.UTF-8 (charmap=UTF-8), LANGUAGE=en_US:en (charmap=UTF-8)
> Shell: /bin/sh linked to /bin/dash
> Init: systemd (via /run/systemd/system)
> 
> Versions of packages caffe-cpu depends on:
> pn  caffe-tools-cpu                  <none>
> ii  libblas3 [libblas.so.3]          3.7.0-2
> pn  libcaffe-cpu1                    <none>
> ii  libopenblas-base [libblas.so.3]  0.2.19-3
> pn  python3-caffe-cpu                <none>
> 
> caffe-cpu recommends no packages.
> 
> Versions of packages caffe-cpu suggests:
> pn  caffe-doc         <none>
> pn  libcaffe-cpu-dev  <none>
>