Usage

Command-line

Alt-Ergo is executed with the following command:

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

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

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

Output

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.

Note

When Alt-Ergo tries to prove a goal (with the native input language), it actually tries to prove the unsatisfiability of its negation. That is why you get unsat answer as an SMT-LIB 2 format output while proving a Valid goal. The same goes for Invalid and sat.

Files extensions

Alt-Ergo supports file extensions:

.psmt2, .smt2 for (our polymorphic extension of) the SMT-LIB 2 standard
.ae, for its native input language (.why and .mlw are now deprecated although still accepted)
.psmt2.zip, .smt2.zip and .ae.zip for compressed files

See the SMT-LIB language and Alt-ergo native language sections for more information about the format of the input files.

Preludes

Preludes can be passed to Alt-Ergo as follows:

$ alt-ergo --prelude p.ae --prelude some-path/q.ae [other-options] file.ae

Alt-Ergo will try to load a local prelude called “p.ae”. 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/q.ae”.

Strict mode

Alt-Ergo supports extensions that are not part of the SMT-LIB standard. For convenience, some of these extensions are enabled by default. Since the version 2.6.0, the flag --strict disables the extensions:

MaxSMT extension for the optimization

We plan to disable more nonstandard extensions with this flag in future versions.

Library

Since version 2.2.0, Alt-Ergo’s library is also compiled and installed. See the API documentation (also available on ocaml.org) for more information.

Javascript

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

Js-node

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.

Js-worker

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.

Inputs

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 }

Outputs

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