BASIC INSTALLATION

1) Once you have unpacked your tarball into a new (sub)directory,
   the first step is to run the "configure" script. If you accept the 
   default compiler options, and plan to run PYTHIA 8 standalone, you 
   only have to type "./configure". This will create the file config.mk. 
   Actually, running this script by hand is optional since "make" will 
   run "configure" anyway, but possible errors in the paths will be 
   less clearly visible.

2) Type "gmake" or "make". This will create an archive library. 
   On Linux systems gmake and make are usually equivalent. For others, 
   in case of doubt, use gmake. This applies below as well.

3) The library should now be ready for use. To study some examples,
   go to the "examples" subdirectory. The README file in that 
   subdirectory contain further instructions how executables can 
   be built and run.
    
4) At any time, typing "gmake clean" will remove all files related to
   the library compilation, including the library itself, but it will
   not reset the configure selections. With "gmake distclean" additionally
   the configure selection is reset, and many other temporary files are
   removed. Output files you may have created during your test runs are
   not affected. (A "gmake clean" is also available in the examples 
   subdirectory, see the README there.) 

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   ADVANCED INSTALLATION

1) If you want to set various compilation options, or prepare the 
   linking to the HepMC external library then the "configure" script 
   will have to do more work. There are two different ways to 
   accomplish this.

1.1)  You can use command-line arguments to set up the desired library 
     links. The possible options are:
     --help : prints a brief summary of the options described here.
     --enable-debug : turns on debugging flags and turns off optimization.
         (This makes program execution much slower. If you later want to 
         switch optimization back on you have to rerun configure without
         this option, since default is to allow optimization.)
     --enable-shared : turns on shared-library creation,
         in addition to the archive libraries always built.
     --enable-64bits : turns on 64 bits compilation flag
         (is automatic on many 64-bit installations, but just in case).
     --lcgplatform=name : allows you to specify the platform assumed for
         compilation, which also affects the assumed location of the 
         libraries below; default is slc4_ia32_gcc34 while other supported
         values for name include slc4_amd64_gcc34 and slc3_ia32_gcc323
         (deprecated). 
     --with-hepmc=path : the path to your local copy of the HepMC library.
         Please note that HepMC version 1 is no more supported. If the path
         does not contain the version number you will be warned about it.    
     --with-hepmcversion=v : a simpler alternative to the above, valid 
         if you are using the CERN AFS LCG external area. See the HepMC
         WEB site for the information about the versions currently
         "in production"
     There also are a few environment variables that you can set to 
     force the configuration process or add flags:
     USRCXXFLAGS : to add flags. Use this variable to add -fPIC to the 
         compilation flags for the static libraries
     USRLDFLAGSSHARED : to add flags to the shared library build command
     USRSHAREDSUFFIX : to force shared libraries suffix to be like this 
         (default on MacOSX is dylib).

1.2) If you want to use the external HepMC from some different location, 
     or it is more convenient to put the paths directly into the script,
     then you have to edit the "configure" file by hand before you run 
     it. Search in the "configure" file for
       HEPMCLOCATION
     and provide the paths where you have the respective libraries
     installed on your local platform.

   Information on the selected paths is stored in the files config.mk,
   examples/config.sh and examples/config.csh when you run "./configure".

2) If you want to change the version of HepMC, you have to
   rerun the script "configure" with relevant options, then type "make" 
   to recompile the library hepmcinterface. If you tried already to run 
   examples with previous versions, pay attention to the environment 
   variable LD_LIBRARY_PATH (see README in examples).

   Hints on how to install HepMC from scratch can be found in the
   separate README.HepMC file.

3) If you have two CPUs or cores on your computer then using the -j2 
   option on make/gmake may speed up compilation.

4) Necessary data are automatically loaded when you use the default 
   PYTHIA installation directory structure and run the main programs in 
   the examples subdirectory. However, in the general case, you must 
   provide the path to the .xml files, originally stored in the xmldoc 
   directory, where default settings and particle data are found. This 
   can be done in two ways.

4.1) You can set the environment variable PYTHIA8DATA to contain the 
     location of the xmldoc directory. In the csh and tcsh shells this 
     could e.g. be
       setenv PYTHIA8DATA /home/myname/pythia81xx/xmldoc
     while in other shells it could be
       export PYTHIA8DATA=/home/myname/pythia81xx/xmldoc
     where xx is the subversion number.
     Recall that environment variables set locally are only defined in 
     the current instance of the shell. The above lines should go into 
     your .cshrc and .bashrc files, respectively, if you want a more 
     permanent assignment.

4.2) You can provide the path as argument to the Pythia constructor in 
     your main program, e.g.
       Pythia pythia("/home/myname/pythia81xx/xmldoc");
     where again xx is the subversion number.

   When PYTHIA8DATA is set it takes precedence, else the path in the 
   constructor is used, else one defaults to the ../xmldoc directory.

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   FOR WINDOWS USERS

The Makefile.msc file is intended for use on Win32/NMAKE systems with 
the  Microsoft Visual C/C++ compiler. This alternative installation
is not the development platform, however, and therefore not as well 
tested. Not all parts of the above installation procedure are the same,
so some experimentation may be required. A few suggestions are found 
in the the separate README.Win32 file.    

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   LEARN MORE

To learn more about the current program:

A) A brief self-contained introduction is found in the 
   htmldoc/pythia8100.pdf file.

B) Details can be found by opening a web browser on the 
   htmldoc/Welcome.html file, and then navigating among the pages 
   in the index there.   

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