Re: No octave prompt (no error messages)

["James R. Phillips" <antiskid56-cygwin at yahoo dot com>]

Robbie Gates wrote:

> Check also that your PATH includes /usr/lib/lapack, as octave appears
> to need the dlls found there.  My default path doesn't contain this,

Lapack is installed in /usr/lib/lapack, which is not on the path by default. 
It is then added to the end of the path at login by
/etc/profile.d/lapack.[sh|csh].

This is a design decision taken so that users may compile their own optimized
atlas libraries, linked with lapack, and install them in /usr/local/bin, which
would normally precede /usr/lib/lapack in the path.  The optimized libraries
would then be used in preference to the generic ones.

Instructions on how to do this are in

/usr/share/doc/Cygwin/lapack-3.0.README

It requires, of course, downloading the lapack source package, and building
from source.  More detailed instructions are in the source package.

Users who insist on trying to use octave outside of the normal bash or c-shell
login process, will likely find it non-functional due to the lapack libraries
not being found.  This may also happen if the user's ~/.profile,
~/.bash_profile, ~/.bashrc, etc, modify the path that is set by default during
the processing of /etc/profile and the scripts in /etc/profile.d.

If cygwin octave is being heavily used, it is really worth building and
installing the optimized libraries.  User reports regarding attempts to do so
would be appreciated.

Some may wonder why pre-built optimized libraries are not available.  The
design of atlas makes this very difficult to do, because atlas wants to
iterativey test its optimizations and customize them to your precise cpu
architecture.  Yes, Debian somehow manages to build and package optimized
libraries, but they do it in a way that subverts the upstream design approach
of atlas.  It _wants_ to optimize to your precise cpu architecture, so you
might as well let it.

James R. Phillips
cygwin lapack/octave packager


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