João Felipe Santos wrote:
On Wed, Nov 19, 2008 at 4:04 PM, Serban Udrea

Hello Serban,

you should check this URL [1] if you want to create a LAPACK/Blas
SlackBuild.

Hello,

And thank you for the hint. I'll take a look.

Until now I did compile lapack 3.1.1(*) and it looks like all tests succeeded except the timing one. I'm not sure how important this is. I'm actually puzzled why such a test is performed. Here is the output, maybe you can give me a hint about its interpretation and/or importance:

Time for 1,000,000 SAXPY ops  =   0.00     seconds
 *** Error:  Time for operations was zero
 Including SECOND, time        =  0.400E-02 seconds
 Average time for SECOND       =  0.800E-03 milliseconds
 Time for 1,000,000 DAXPY ops  =  0.400E-02 seconds
 DAXPY performance rate        =   250.     mflops
 Including DSECND, time        =  0.400E-02 seconds
 Average time for DSECND       =   0.00     milliseconds
 Equivalent floating point ops =   0.00     ops


This one works, but was written by the Slacky.eu
community, and their style of writing SlackBuilds is different from
the SBo style. I want to create a SlackBuild for ATLAS, and want to
make it compatible with a previous LAPACK/Blas installation (so I
don't need to recompile LAPACK when compiling ATLAS). If you need some
help for doing this, let me know.


If I understand you well, you already have lapack/blas installed but would like to have the ATLAS implementation of blas for the performance gain, and you don't want to recompile lapack against ATLAS? In this case you may have problems, which may arise from differences in compiler flags, as stated in section 3.1.1 of ATLAS's compilation instructions.

I have to say, that I don't realy understand section 3.1.1 in the installation instructions for ATLAS. It is written there about installing first lapack and then ATLAS. But lapack depends on blas, if I'm not mistaken, and needs an already installed/compiled blas implementation. On the other hand ATLAS is a blas implementation. Thus I don't realy get it(**), and this is why I stick for the time beeing with the netlib implementation as delivered with the lapack source tree.

Best regards,

Serban

(*) I didn't go for 3.2 because I use to be somehow conservative and expect there may be some bugs to be squeezed out of 3.2. There seem to be also some API changes too. I also compiled blas from the lapack tree, did not try ATLAS.

(**) Might it be that ATLAS just automaticaly substitutes the blas libraries created during lapack compilation?
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