Re: forcing local build from a package definition

[Eric Bavier <ericbavier@gmail.com>]

Federico Beffa writes:

> Hi,
>
> I'm preparing a package for ATLAS (Automatically Tuned Linear Algebra
> Software).  The library provides functions from LAPACK which are automatically
> speed optimized for the hardware on which the library is built (the
> optimization takes place during the build phase).

ATLAS provides only a handful of the LAPACK routines.  The primary
focus is on BLAS routines.  In order for ATLAS to provide a full lapack
experience, it needs to be configured with the netlib lapack (which is
where our current lapack package comes from).

> My question is the following: is there a way to force a local build from a
> package definition (without having to pass '--no-substitutes' to
> guix)?

I don't think this is necessary...

> If not, what do you think about explicitly stating in the description of the
> package that it MUST be installed with the '--no-substitutes' flag and, if the
> user does not do so, hydra may provide a package which does not run on the
> user hardware?

ATLAS frequently pulls its tuning configuration information from a table
of known values at configuration time.  I think there is also a way to
tell it which architecture it should be built for.

> Most other distributions deliver binary packages which have been compiled for
> a very general CPU.  However, this not satisfactory since it results in a much
> slower library.  Guix is in a nice position to provide a good performance
> version of the library and I think we should do so.

You may be interested in exploring the BLIS library,
https://code.google.com/p/blis/.  It doesn't require build-time
performance-tuning, and often significantly outperforms ATLAS
http://www.cs.utexas.edu/users/flame/pubs/BLISTOMSrev2.pdf

-- 
Eric Bavier

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