Cosmic string network simulation and gravitational backreaction code
from the Tufts Institute of Cosmology.

Major developers: Ken Olum, J. J. Blanco-Pillado, Ben Shaer, Jeremy
Wachter, Asier Lopez-Eiguren.

With contributions by: Shaojiang Wang, Colette Kaya, Vishnu Gade,
Kirthi Sivakumar.

The original concept was due to Alex Vilenkin, and the original
implementation of the concept was done by Vitaly Vanchurin.

INSTALLATION

You need a lisp implementation.  Many things in the code expect you to
have SBCL, so install it from sbcl.org.

You need to install the "quicklisp" system, which is needed in
particular for gsll, the Gnu scientific library in lisp.  To get it,
download the file https://beta.quicklisp.org/quicklisp.lisp into your
home directory.  Then in your lisp, say (load "~/quicklisp") and then
(quicklisp-quickstart:install).  Each user of this package has to do
this, but only once each.

You will need access to gsl (the Gnu scientific library), libffi,
gnuplot, and ffmpeg (if you want to make movies), so install these
packages.

CONFIGURATION

To configure the system for your site, find the code in 
(defparameter server ...) in definitions.lisp and add a conditional to
identify your site and return some keyword identifying it.  Then look
for all uses of :tufts in definitions.lisp and submit.lisp and add
additional clauses for your site.  For long time, Tufts has been using
the slurm batch manager.  The code ran once under lsf and under
condor. If you use one of those, you should try selecting this old
code and seeing if it works.  But it might need modification.  If you
have yet some other match manager, your will have to write some
functions to interface to it.

RUNNING SIMULATIONS

To load the system, connect to the directory with the lisp files and in
your lisp say

(load "load")

To run a small simulation in your lisp, say something like
(do-vv :size 20)

This will put the output files in a directory "test" under your
current directory.  After the first time you also need the option
:OVERWRITE T, or it will complain that that output file already
exists.

To run a real simulation, you need the manager.  For example,
(manager "test" t 70
   '(do-vv :size 100.0 :log t :split-factor 5))

The arguments to MANAGER mean the following:

First is the directory to keep the temporary files and write the output.
It is relative to variable batch-root-directory, which you should
configure properly for your site.

Second is the duration of the run in internal time.  The units are
roughly units of the initial string spacing.  The symbol T means to
default the time from the size of the run.

Third is the maximum number of worker processes to allow at once.

Last comes the (quoted) form that is to be evaluated in each worker.  It
will be amended with a :job-number argument to say which job the worker
is to do.

The SIZE argument to DO-VV gives the size of the box (really the minimum
distance between identifying points under periodic boundary conditions,
because the box is not rectangular).  SPLIT-FACTOR gives the factor by
which to divide the size in each linear direction to split up the entire
work into jobs.  Thus in this case there will be 125 workers in
each layer. (See the picture in our paper in Journal of Computational
Physics to understand what layers are.)

There are many other possible arguments to DO-VV.  They are defined by
the forms DEFINE-SIMULATE-ARGUMENT and DEFINE-SIMULATE-VARIABLE, which
you can look for in the source.  In the example above, LOG means to
write a log of loops that were created.

UPGRADING

If you install a new version of sbcl, your compiled files will not work.
So recompile everything by saying (load "reload").

Sometimes new versions of sbcl require new versions of gsll.  It would
probably work to say (ql:update-dist "quicklisp") to get a new
version.  However, when I did this I interrupted it and got into some
inconsistent state.  So I started completely over by deleting my
~/quiclklisp directory and reinstalling as above, starting
with (load "~/quicklisp").