flatzinc.html

---
layout: default
title: GECODE flatzinc
headline: FlatZinc
---

{% assign GECODESTAMP = site.data.versions["gecodestamp"] %}

<section class="page-section">
  <p>
    FlatZinc is a low-level modelling language for constraint problems. It is
    designed to be easily interfaceable to constraint solvers (like Gecode).
    For more information on FlatZinc, please refer to
    <a href="https://www.minizinc.org/">the MiniZinc pages of the G12 project</a>.
  </p>

  <p>
    We provide a parser that reads a FlatZinc model from a file, and returns a
    Gecode Space object that represents the model. We also provide a simple
    front-end, an executable program that reads a FlatZinc model and prints
    the solution (if any) on the standard output.
  </p>
</section>

<section class="page-section">
  <h2>FlatZinc for Gecode</h2>

  <p>
    Starting with Gecode version 3.2.0, the FlatZinc interpreter for Gecode
    is part of the standard Gecode distribution.
    Please check our <a href="{{ '/download.html' | relative_url }}">download pages</a> for more
    information on how to get a copy of Gecode.
  </p>

  <p>
    The FlatZinc interpreter that ships with Gecode version {{ GECODESTAMP }}
    supports the FlatZinc language and the MiniZinc global constraint
    definitions included in the source release.
  </p>
</section>

<section class="page-section">
  <h2>Running the parser</h2>

  <p>
    The executable is called fzn-gecode. You can run it with the -help switch
    to get an overview of how to invoke it:
  </p>

<pre>
$ fzn-gecode -help
Gecode FlatZinc interpreter

Gecode configuration information:
 - Version: {{ GECODESTAMP }}

 - Variable types: BoolVar IntVar SetVar FloatVar
 - Trigonometric and transcendental float constraints: enabled
 - Thread support: enabled (8 processing units)
 - Gist support: enabled

Options for Gecode/FlatZinc:
        -help, --help, -?
                print this help message
        -n (unsigned int) default: 1
                number of solutions (0 = all)
        -p (double) default: 1
                number of threads (0 = #processing units)
        -c-d (unsigned int) default: 8
                recomputation commit distance
        -a-d (unsigned int) default: 2
                recomputation adaption distance
        -a (optional: false, 0, true, 1) default: false
                return all solutions (equal to -solutions 0)
        --free (optional: false, 0, true, 1) default: false
                no need to follow search-specification
        -decay (double) default: 1
                decay factor
        -node (unsigned int) default: 0
                node cutoff (0 = none, solution mode)
        -fail (unsigned int) default: 0
                failure cutoff (0 = none, solution mode)
        -time (unsigned int) default: 0
                time (in ms) cutoff (0 = none, solution mode)
        -interrupt (optional: false, 0, true, 1) default: true
                whether to catch Ctrl-C (true) or not (false)
        -r (int) default: 0
                random seed
        -restart (none, constant, linear, luby, geometric) default: none
                restart sequence type
        -restart-base (double) default: 1.5
                base for geometric restart sequence
        -restart-scale (unsigned int) default: 250
                scale factor for restart sequence
        -mode (solution, stat, gist) default: solution
                how to execute script
        -s (optional: false, 0, true, 1) default: false
                emit statistics
        -o (string) default: NONE
                file to send output to
</pre>
</section>

<section class="page-section">
  <h2>Global constraint definitions for MiniZinc</h2>

  <p>
    The MiniZinc-to-FlatZinc converter provided by the G12 project can produce
    specialized FlatZinc that is targeted at a certain solver. Gecode/FlatZinc
    provides suitable definitions of global constraints in the directory
    <code>mznlib</code>. This directory is located in the Gecode directory
    installed under &lt;prefix&gt;/share/gecode.
  </p>

  <p>
    In order to make the MiniZinc-to-FlatZinc converter aware of these global
    constraint definitions, you can either
  </p>

  <ul class="simple-list">
    <li>
      Copy the <code>mznlib</code> directory into the <code>lib/minizinc</code>
      directory of your MiniZinc installation, rename it to <code>gecode</code>, and
      use the <code>-G gecode</code> flag of <code>mzn2fzn</code>;
    </li>
    <li>
      Use the <code>-I</code> flag of <code>mzn2fzn</code> with the complete
      path to the <code>mznlib</code> directory;
    </li>
    <li>
      Use the <code>mzn-gecode</code> script, which will invoke
      <code>mzn2fzn</code> with the correct library paths and directly pass the
      resulting FlatZinc on to the Gecode FlatZinc interpreter.
    </li>
  </ul>
</section>

<section class="page-section">
  <h2>FlatZinc parser skeleton</h2>

  <p>
    We also provide the source code of the Gecode FlatZinc parser, stripped of
    all Gecode-specific code. You can use it as a starting point for your own
    FlatZinc interpreter.
  </p>

  <p>
    The source code archive (compatible with FlatZinc 1.5) is available here:
  </p>

  <ul class="simple-list">
    <li><a href="{{ '/download/flatzinc_skeleton-1.3.zip' | relative_url }}">flatzinc_skeleton-1.3.zip</a></li>
  </ul>

  <p>
    The archive contains a README file that explains how to adapt and compile
    the code. If you have any questions, please contact
    <a href="mailto:tack@gecode.dev">tack@gecode.dev</a>.
  </p>
</section>