README file for the 'linboxing' GAP4 package
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Paul Smith 
paul.smith@nuigalway.ie
23 April 2008


1. OVERVIEW

The linboxing package for GAP provides a kernel-level interface to the 
LinBox C++ exact linear algebra library (http://www.linalg.org). It
provides alternative versions of some GAP linear algebra routines that 
are considerably faster than the equivalent GAP versions.

It is implemented in GAP, C and C++.

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2. BEFORE INSTALLATION

Before installing the linboxing package, you need to have the LinBox C++ 
library (at least version 1.1.5) installed. LinBox can be downloaded from
    http://www.linalg.org
and to build it you will also need to have the GNU Multiprecision (GMP) library 
and a version of the BLAS linear library installed. Installation instructions 
are provided on the LinBox website, or with the downloaded archive.

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3. INSTALLATION

To get the newest version of this GAP 4 package download one of the archive 
files
    linboxing-x.x.tar.gz
    linboxing-x.x.zoo
    linboxing-x.x.tar.bz2
    linboxing-x.x.zip
and unpack it using 
    gunzip linboxing-x.x.tar.gz; tar xvf linbox-gap-x.x.tar
respectively
    unzoo -x linboxing-x.x.zoo
and so on.

Do this in a directory called 'pkg', preferably (but not necessarily) in the 
'pkg' subdirectory of your GAP 4 installation. It creates a subdirectory called 
'linboxing-x.x'.

To install this package do
    cd linboxing-x.x
    ./configure 
    make

The package will not work without this step.

If you installed the package in another 'pkg' directory than the standard 'pkg' 
directory in your GAP 4 installation, then you have to add the path to the 
directory containing your 'pkg' directory to GAP's list of directories. This 
can be done by starting GAP with the '-l' command line option followed by the 
name of the directory and a semicolon. Then your directory is prepended to the 
list of directories searched. Otherwise the package is not found by GAP. Of 
course, you can add this option to your GAP startup script.

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4.  RUNNING GAP WITH LINBOX

The memory management in LinBox conficts with that in GAP, and if you run
GAP with the standard settings and try to use the linboxing package, you are 
likely to find that it exits abruptly with the message 'cannot extend the 
workspace any more'. There are (currently) two solutions to this problem:

- Allocate GAP a large workspace 
The -m command-line switch tells GAP to allocate a certain number of bytes
to the GAP workspace when it starts up. If this is sufficiently large, GAP 
will not need to extend its workspace further, and will not conflict with 
LinBox. For example,
    gap -m 256M 
will allocate 256Mb to GAP when it starts.

- Allocate some special memory for LinBox to use
The -a command-line switch tells GAP to set aside a certain number of bytes
for 'malloc', which is the type of memory that LinBox uses. LinBox can then
use this memory without interfering with GAP's own memory. For example,
    gap -a 50M
will allocate 50Mb for LinBox to use.

The linboxing package is not loaded by default. To load the linboxing package,
run GAP and type
    LoadPackage("linboxing");
You can put this command into your .gaprc file if you plan to use the linboxing
package often.

Before using the package for any serious calculation, you should check its
correct operation by running the test suite. This can be run from within GAP
by typing
    TestLinBox();

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5.  DOCUMENTATION

See the doc/ directory of the linboxing package for further documentation in 
various formats. The documentation can also be downloaded from the package 
website.

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