
                                Building SWIFT
                                ==============

SWIFT is built from a clean source repository using the commands:

   ./autogen
   ./configure
   make

and from a distribution tarball using:

   ./configure
   make

The compiler choice is GCC by default, but that can be changed using the "CC"
environment variable. This can be just set, or passed on the ./configure
command line, i.e.:

   bash:
      export CC=icc
      ./configure

   [t]csh:
      setenv CC=icc
      ./configure

or:

   ./configure CC=icc

to use an Intel compiler. The main "programs" can be found in the "examples/"
directory. See README for run parameters.

SWIFT has been successfully built and tested with the following compilers:

  - GCC 4.8.x  
  - Intel ICC 15.0.x
  - clang 3.4.x 

More recent versions and slightly older ones should also be able to
build the software.

By default an attempt to choose suitable set of optimizing compiler flags
will be made, targeted for the host machine of the build. If this doesn't
work or the binaries will for another architecture then you can stop the
selection of flags using:

   ./configure --disable-optimization

and then supply your own flags using the "CFLAGS" environment variable, as for
CC.

Note that any CFLAGS that you supply will be added to those determined by
configure in all circumstances. To build SWIFT with debugging support you
can use:

    ./configure --enable-debug --disable-optimization

You could also add some additional flags:

    ./configure --enable-debug --disable-optimization CFLAGS="-O2"

for instance. GCC address sanitizer flags can be included using the 

    ./configure --enable-sanitizer

option. Note this requires a GCC compiler version of at least 4.8.

By default vectorization is switched on. The highest instruction set
available on the platform will be automatically used. However, not all
implementations of SPH available in the code have vectorized
routines. Vectorization will have to be switched off for these. It can
also be switched off for benchmarking purposes. To do so, you can use:

    ./configure --disable-vec


                                 Dependencies
                                 ============

SWIFT depends on a number of third party libraries that should be available
before you can build it.


HDF5: a HDF5 library (v. 1.8.x or higher) is required to read and write
particle data. One of the commands "h5cc" or "h5pcc" should be
available. If "h5pcc" is located them a parallel HDF5 built for the version
of MPI located should be provided. If the command is not available then it
can be located using the "--with-hfd5" configure option. The value should
be the full path to the "h5cc" or "h5pcc" commands.


MPI: an optional MPI library that fully supports MPI_THREAD_MULTIPLE.
Before running configure the "mpirun" command should be available in the
shell. If your command isn't called "mpirun" then define the "MPIRUN"
environment variable, either in the shell or when running configure.

The MPI compiler can be controlled using the MPICC variable, much like
the CC one. Use this when your MPI compiler has a none-standard name.


METIS: a build of the METIS library can be optionally used to optimize the
load between MPI nodes (requires an MPI library). This should be found in
the standard installation directories, or pointed at using the
"--with-metis" configuration option.  In this case the top-level
installation directory of the METIS build should be given. Note to use
METIS you should at least supply "--with-metis".


libNUMA: a build of the NUMA library can be used to pin the threads to
the physical core of the machine SWIFT is running on. This is not always
necessary as the OS scheduler may do a good job at distributing the threads
among the different cores on each computing node.


DOXYGEN: the doxygen library is required to create the SWIFT API
documentation.



                             SWIFT Coding style
                             ==================

The SWIFT source code is using a variation of the 'Google' style. The
script 'format.sh' in the root directory applies the clang-format-3.8
tool with our style choices to all the SWIFT C source file. Please
apply the formatting script to the files before submitting a merge
request.
