Add README for jacop

solvers/jacop/README

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+The solver "jacop" uses JaCoP (http://jacop.osolpro.com/) to solve
+constraint programming problems.  Normally the jacop solver is
+invoked by AMPL's solve command, which gives the invocation
+
+     jacop stub -AMPL
+
+in which stub.nl is an AMPL generic output file (possibly written
+by "ampl -obstub" or "ampl -ogstub").  After solving the problem,
+the solver writes a stub.sol file for use by ampl's solve and solution
+commands.  When you run ampl, this all happens automatically if you
+give the AMPL commands
+
+     option solver jacop;
+     solve;
+
+You can control the solver by setting the environment variable
+jacop_options appropriately (either by using ampl's option command,
+or by using the shell's set and export commands before you invoke ampl).
+You can put one or more (white-space separated) phrases in
+$jacop_options.  A few of the phrases are single words:
+
+     Phrase       Meaning
+
+     version      Report version details before solving the problem.
+
+Others are name-value pairs, possibly separated by '=', as in
+
+     wantsol 1
+or
+     wantsol=1
+or
+     wantsol = 1
+
+any of which make the jacop driver write .sol file in a stand-alone
+invocation (no -AMPL on the command line).
+
+The following command prints the full list of options with descriptions:
+
+     jacop -=
+
+-----------------------
+solve_result_num values
+=======================
+
+Here is a table of solve_result_num values that "jacop" can return
+to an AMPL session, along with the text that appears in the associated
+solve_message.
+
+        Value   Message
+
+          0     optimal solution
+        100     feasible solution
+        200     infeasible problem
+        600     interrupted
+
+-------------------
+
+If you invoke "jacop stub -AMPL" or "jacop stub", you can also
+supply additional command-line arguments of the form name=value.
+Such arguments override specifications in $jacop_options.  Example:
+
+     ampl -obfoo foo.model foo.data
+     nohup jacop -s foo 2>>err&
+
+to solve a problem whose solution will take a while; after it finishes,
+
+     ampl foo.model foo.data -
+     solution foo.sol;
+     display ... /* things involving the computed solution */;
+
+(Here, - denotes standard input, and ampl reads the "solution..."
+and "display..." lines.)
+
+*************************
+
+If you have questions about or find bugs with this stuff,
+please contact:
+
+     Victor Zverovich
+     [email protected]