INSTALL

INSTALL Guide 

Version 1.2.5, August 22, 2020
Version 1.2.4, May 11, 2015
Version 1.2.0, January 7, 2011
Version 1.0, December 22, 2009
Version 0.3, September 17, 2009
Version 0.2, May 8, 2009
Version 0.1, March 28, 2009

COMPILING JBLAS (JAVA PART)
===========================

Prerequisites: 
  - java JDK
  - ant
  - maven
  - ruby

MAVEN BUILD
-----------

Just the usual "mvn clean install" builds everything and installs the jar
file in your local repository.


INSTALLING JBLAS
----------------

1. Add "jblas-1.2.5.jar" to your CLASSPATH

2. By default, the dynamic libraries are extracted from the jar file
   to the default temporary directory and loaded from there. If you
   don't want to do this, extract the dynamic library from jblas-1.2.5.jar
   and copy it somewhere where it can be found.

   For Linux, use LD_LIBRARY_PATH, for Windows, PATH


ANT BUILD
---------

(Ant build is only used for historical purposes, and to trigger the
regeneration of Float variants from Double files)

Running "ant clean jar" should do the job ;)

"ant jar" collects all static JNI libraries. Other build targets are:

- ant dynamic-lean-jar
  
  Build a jar file with the JNI libraries, but without the ATLAS libraries
  built in for only the current platform.

- ant static-lean-jar

  Build a jar file with the JNI and ATLAS libraries only for the current
  platform.

- ant minimal-jar

  Build a jar file without the JNI and ATLAS libraries. Both must be
  installed in the usual library locations.



COMPILING THE NATIVE PART
=========================

I assume that you already have a built of lapack-lite or ATLAS based
on the lapack-lite libraries. That build process is quite
involved. You can find some information about it in
BUILDING_ATLAS. You can also use the atlas libraries which come with
your distribution.

The build goes like this:

- run ./configure with options (see below)
- run "make clean all" to build the JNI library
- run "mvn clean package" to package the library into the jar file


BUILD OPTIONS
-------------

Dynamic vs. Static

Basically, you can build with "dynamic" binding or "static" binding,
which means that either the JNI library is dynamically loading the
lapack libraries, or they are already linked into it. The latter case
("static") is better for standalone cases, but the resulting jar file
is bigger.

The default is static binding, otherwise pass the option
"--dynamic-libs" to the configure script. (The flag --static-libs is
still recognized for backwards compatability reasons.)

This option also affects what libraries "ant jar" packs into the jar file.


LAPACK build vs. ATLAS build

Starting with 1.2.5, the default build is now to link against openblas.

You can either build against LAPACK only, or against the ATLAS
libraries. LAPACK is somewhat slower, but probably easier to
compile. To compile against LAPACK, pass the "--lapack-build"
option. I also recommend to use the "--libpath" option to specify
exactly where the libraries are.


CONFIGURE FLAGS SUMMARY

The configure script understands the following options:

--lapack=DIR
   Location where the LAPACK and BLAS sources can be found. Location of
   the extracted lapack-lite files. Otherwise it is assumed that they
   can be found in the jblas directory

--lapack-build
   Build only against LAPACK and BLAS, not ATLAS. Note that depending on
   your configuration, you might still get an ATLAS version (for example, when
   you compile under debian and ATLAS is installed). Use --static-libs then.

--download-lapack
   Download and unpack lapack-lite here if not found.

--dynamic-libs
   Links all libraries statically.

--static-libs [default starting with 1.2.5]
   Searches for static libraries only. Resulting jblas will not depend on
   shared LAPACK/BLAS/ATLAS libraries. Libraries that cannot be merged into the
   library are copied into the jar and loaded at runtime.

--ptatlas
   Uses multithreaded versions of the ATLAS libraries. AFAIK, these should
   be compiled on the target computer to have the right number of threads.
   This means you have to recompile ATLAS, but it is certainly worth
   the effort, performance improvements are really huge!

--help
   print help

--libpath=DIR1:DIR2:...
   Specify the directory where the files will lie

--build-type=TYPE
   Tweak the libraries to look for. TYPE is one of atlas, lapack, openblas, and nvblas

--libs=LIB1,LIB2,...

Building against different versions of LAPACK and BLAS libraries. In principle,
using these flags you can fully specify which libraries to try in which directories.
The configure script will then go through those libraries in the specified directories
and look whether it can find a few core methods.

The --built-type flag presets the libraries a bit, but otherwise doesn't change much.

Once configured with the --static-libs flag, "make all" links against the libraries
and copies the resulting shared library to the corresponding directory to be included
with the resulting jar file.


SOME INTERNAL NOTES
-------------------

Here is some of the stuff that happens

- configure executes the Ruby scripts in the config directory to generate
  configure.out
- configure.out is used by the Makefile to set the right variables
- make clean all also reconstructs the files using "ant javah" to generate
  the headers
- maven can be used to compile the Java portion of Java, but it calls into
  ant which runs the ruby scripsts class_to_float.rb and static_class_to_float.rb
  to construct Float variants of many Double classes, or fill in float based
  code in classes like org.jblas.Eigen
- last time I checked, I needed to build the final libs on an older version of
  CentOS so that it runs on Linux 2.6