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The solver jacop uses Java Constraint Programming solver (JaCoP) to solve constraint programming problems. It fully supports AMPL extensions for logic and constraint programming. Solver binaries are available for download from the Open Source Solvers page.

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;

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) option assignments in $jacop_options. The option version doesn't take a value:

Phrase Meaning
version Report version details before solving the problem.

Others are name-value pairs separated by '=', as in


which limits solution time to 600 seconds.

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 (for an optimization problem) or feasible solution (for a satisfaction problem)
100 feasible solution
200 infeasible problem
400 limit
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.)