Since version 2.2.0, Alt-Ergo’s library is also compiled and installed. See the API documentation for more information.


Alt-Ergo and AltGr-Ergo are executed with the following commands, respectively:

    $ alt-ergo   [options] file.<ext>
    $ altgr-ergo [options] file.<ext>

The CDCL solver is now the default SAT engine. The commands below allow to enable the old Tableaux-like SAT-solver:

    $ alt-ergo   [options] --sat-solver Tableaux file.<ext>
    $ altgr-ergo [options] --sat-solver Tableaux file.<ext>

Files extensions

Alt-Ergo supports file extensions:

  • .ae, for its native input language (.why and .mlw are now depreciated although still accepted)

  • .psmt2, .smt2 for (our polymorphic extension of) the SMT-LIB 2 standard

See the Input section for more information about the format of the input files


The results of an Alt-ergo’s execution have the following form :

File "<path_to_file>/<filename>", line <l>, characters <n-m>: <status> (<time in seconde>) (<number of steps> steps) (goal <name of the goal>)

The status can be Valid, Invalid or I don't know. If the input file is in the SMT-LIB 2 format the status will be either unsat, sat, unknown. You can force the status to be print in the SMT-LIB 2 form with the option --output smtlib2.


See the AB-Why3 README file for the documentation of the AB-Why3 plugin

The Fm-Simplex plugin can be used as follows:

    $ alt-ergo --inequalities-plugin fm-simplex-plugin.cmxs [other-options] file.<ext>
    $ alt-ergo --inequalities-plugin some-path/fm-simplex-plugin.cmxs [other-options] file.<ext>

Alt-Ergo will try to load a local plugin called “fm-simplex-plugin.cmxs”. If this fails, Alt-Ergo tries to load it from the default plugins directory (run alt-ergo --where plugins to see its absolute path). You can also provide a relative or an absolute path as shown by the second command above. Also, you should replace “.cmxs” by “.cma” if you are working with bytcode binaries.


Preludes can be passed to Alt-Ergo as follows:

    $ alt-ergo --prelude --prelude some-path/ [other-options]

Alt-Ergo will try to load a local prelude called “”. If this fails, Alt-Ergo tries to load it from the default preludes directory (run alt-ergo --where preludes to see its absolute path). You can also provide a relative or an absolute path as shown by “some-path/”.

For instance, the following command-line enables floating-point arithmetic reasoning in Alt-Ergo and indicates that the FPA prelude should be loaded:

    $ alt-ergo --use-fpa --prelude <>

Plugins and Preludes directories

As stated above, the --where option of alt-ergo can be used to get the absolute path that is searched by default when looking for plugins and preludes that were given with a relative path. It is useful to know that these two directories are actually relative to the location of the alt-ergo executable, so that the executable, as well as preludes and plugins, can be relocated.

For instance, on a Linux system, assuming the alt-ergo executable is at some path some/path/bin/alt-ergo, theses directories are respectively located at some/path/share/alt-ergo/plugins/ and some/path/share/alt-ergo/preludes/. On windows, a binary at path Z:\some\path\bin\alt-ergo will look for preludes and plugins in Z:\some\path\share\alt-ergo\preludes and Z:\some\path\share\alt-ergo\plugins respectively.


Alt-Ergo can be compiled in Javascript see the install section for more informations.


The Javascript version of Alt-Ergo compatible with node-js is executed with the following command:

    $ node alt-ergo.js  [options] file.<ext>

Note that timeout options and zip files are not supported with this version because of the lack of js primitives.


A web worker of the alt-ergo solver is available with the command make js-worker. It uses Js_of_ocaml Worker’s and Lwt. The data-encoding library is used to encode and decode messages to/from the worker. Since the messages are in JSon format, the Alt-Ergo worker can be used from any javascript code.


This web worker takes a json file composed of a list of string representing each line of an input file. This json file can also be composed of an optional worker identifier (integer) and an optional name for the file to solve. The following code shows an example of a such json file :

{"filename": "testfile",
 "worker_id": 42,
 "content": [ "goal g : true" ] }

The worker also take a Json file that correspond to the options to set in Alt-Ergo, like the following example :

{"debug": true,
 "sat_solver": "Tableaux",
 "steps_bound": 1000 }


At the end of solving it returns a Json file corresponding to results, debug informations, etc:

{"worker_id": 42, "status": { "Unsat": 0 },
"results": [ "Valid (0.1940) (0 steps) (goal g)", "" ],
"debugs": [ "[Debug][Sat_solver]", "use Tableaux-like solver", "" ],
"model": [ "[all-models] No SAT models found", "" ],
"unsat_core": [ "unsat-core:", "", "", "" ],
"errors": [ "" ],
"warnings": [ "" ],
"statistics": [ [], [] ] }

Options and results formats are available in worker_interface module. In this module you can also find functions to easily encode inputs and decode outputs. Look at the worker_json_example.json in the ressources rsc of the project to learn more.

Js-worker example

A small example of how to use the Alt-Ergo web worker can be build with the command make js-example. This command also makes the web worker if it has not already been built. It produces a www directory with an html page where you can write a small example, run the worker, and see the results. You can also look at the console of your browser to look at the json file sent