= WHIZARD Installation instructions =

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Here we collect informations about the WHIZARD installation procedure. Most of this can be found as well in the [source:tags/release_2.0.2/INSTALL INSTALL file] as well
as in the [http://projects.hepforge.org/whizard/manual.pdf manual.]

We review here the installation of the tarball of the latest version of WHIZARD 2.
Technical details about the installation of the development version from the SVN trunk can be found in the [http://projects.hepforge.org/whizard/manual.pdf manual.]

The philosophy of WHIZARD 2 is that the program is installed centrally in a computer, e.g. in a directory {{{/usr/local/}}}, where all the binaries, libraries and necessary files are located, while the users run the program in workspaces in their home directories. (Working in batch mode can be handled, too.) The following
describes a system installation, but of course a user can install WHIZARD also in his/her home directory.

=== Prerequisites ===

The general prerequisites for the installation are standard tools 
for software development like {{{make}}} etc., and two different compilers, a  
Fortran 2003 for the WHIZARD core and its corresponding
libraries as well as the O'Caml compiler for the O'Mega matrix
element generator. Please note that versions of WHIZARD / O'Mega up to 2.0.2 are incompatible with O'Caml versions 3.12.0+. Details and links for the compilers can be found 
[http://projects.hepforge.org/whizard/compilers.html here.]

=== Configuration ===

After you downloaded the most recent tarball from the main page,
unpack it, go to the WHIZARD directory, create a new {{{build}}}
directory and go there. In that directory, perform a
{{{../configure FC=<your FORTRAN compiler> --prefix=/usr/local}}}. 
Note that this is because the source and compile directories should be
different to avoid any problems during compilation and
installation. {{{../configure --help}}} shows you the options for the
configure process you have. The {{{FC}}} environment variable
allows you to specify your FORTRAN compiler of choice. Note that
WHIZARD 2 has been written in Fortran 2003 in a fully
object-oriented way. We highly recommend usage of the standard
{{{gfortran}}} compiler from version 4.5.0 on. You can access the
help menu of configure by {{{../configure --help}}}. 
{{{./configure -V}}} shows you the actual version of
your downloaded WHIZARD distribution. The possible environment
variables are:

{{{
  CC          C compiler command
  CFLAGS      C compiler flags
  LDFLAGS     linker flags, e.g. -L<lib dir> if you have libraries in a
              nonstandard directory <lib dir>
  LIBS        libraries to pass to the linker, e.g. -l<library>
  CPPFLAGS    C/C++/Objective C preprocessor flags, e.g. -I<include dir> if
              you have headers in a nonstandard directory <include dir>
  CPP         C preprocessor
  FC          Fortran compiler command
  FCFLAGS     Fortran compiler flags
  F77         Fortran77 compiler command 
  FFLAGS      Fortran77 compiler flags
  CXX         C++ compiler command
  CXXFLAGS    C++ compiler flags
  CXXCPP      C++ preprocessor
}}}

For most of these there is no need to be set during installation. 

The configure process checks for the build and host system type; only
if this is not detected automatically, the user would have to specify
this by himself. After that system-dependent files are searched for,
LaTeX and Acroread for documentation and plots, the FORTRAN compiler 
is checked, and finally the O'Caml compiler. The next step is the
checks for external programs like {{{LHAPDF}}} and {{{HepMC}}}.
Finally, all the Makefiles are being built. 

Note that parts of the WHIZARD do contain good old {{{Fortran77}}}
code, e.g. the PYTHIA bundle for showering and hadronization. These
parts should better be compiled with the very same {{{Fortran2003}}}
compiler as the WHIZARD core. There is, however, one subtlety: 
when the {{{configure}}} flag {{{FC}}} gets a full system path as
argument, {{{libtool}}} is not able to recognize this as a valid (GNU)
{{{Fortran77}}} compiler. It then searches automatically for binaries 
like {{{f77}}}, {{{g77}}} etc. or a standard system compiler. This 
might result in a compilation failure of the {{{Fortran77}}}. A viable
solution is to define an executable link and use this (not the full
path!) as {{{FC}}} flag.

=== Compilation and Installation ===

The compilation is done by invoking {{{make}}} and finally
{{{make install}}}. You could also do a {{{make check}}} in
order to test whether the compilation has produced sane files on your
system. This is highly recommended, but need to be done only for the 
first installation. 

Be aware that there be problems for the installation if the install
path or a user's home directory is part of an AFS file system. Several
times problems were encountered connected with conflicts with
permissions inside the OS permission environment variables and the AFS
permission flags which triggered errors during the {{{make install}}}
procedure. Also please avoid using {{{make -j}}} options of parallel
execution of {{{Makefile}}} directives as AFS filesystems might not be 
fast enough to cope with this.


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