[Bug 376739] Re: matrix multiplication with libatlas gives wrong result for big matrices

[FP]

In response to https://bugs.launchpad.net/ubuntu/+source/atlas/+bug/376739/comments/2
I suspect /usr/lib/sse2/atlas/liblapack.so.3gf has nothing to do with that bug.
The faulty lib is /usr/lib/sse2/atlas/libblas.so.3gf
- If libblas3gf is not installed, then the command
    (export LD_LIBRARY_PATH=/usr/lib/sse2; ./atlas-test)
gives wrong result, because wrong /usr/lib/sse2/atlas/libblas.so.3gf is used.
- If libblas3gf is installed, then the commands
    (export LD_LIBRARY_PATH=/usr/lib; ./atlas-test)
    (export LD_PRELOAD=/usr/lib/libblas.so.3gf;./atlas-test)
give good result, because /usr/lib/libblas.so.3gf is used.

There is a regression
libatlas3gf-sse2_3.6.0-22ubuntu1_i386 -> good
libatlas3gf-sse2_3.6.0-22ubuntu2_i386 -> wrong
Cf. https://bugs.launchpad.net/debian/+source/atlas/+bug/406520/comments/3

Atlas library should be compiled using the processor which wil be used for.
Hence distributing such a precompiled package is not optimal.

Also, atlas is a very delicate piece of code. All atlas packages
should depend on package libatlas-test, and all tests should be passed
before installation can be finished.
Imagine the result of a an engineer computation of the structure of a bridge
or of a composite plane using a faulty atlas library!

A very small piece of code is gived at comment
https://bugs.launchpad.net/debian/+source/atlas/+bug/406520/comments/1
and attached here.



** Attachment added: "t.f"
   http://launchpadlibrarian.net/34325646/t.f

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matrix multiplication with libatlas gives wrong result for big matrices
https://bugs.launchpad.net/bugs/376739
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