options.rst

Command Line Options

Here is an overview of the command-line options that Leon recognizes:

Choosing which Leon feature to use

The first group of options determine which feature of Leon will be used. These options are mutually exclusive. By default, --verify is chosen.

• --eval

  Evaluates parameterless functions and value definitions.

• --verify

  Proves or disproves function contracts, as explained in the :ref:`verification` section.

• --repair

  Runs program :ref:`repair <repair>`.

• --synthesis

  Partially synthesizes choose() constructs (see :ref:`synthesis` section).

• --termination

  Runs a simple termination analysis.

• --xlang

  Transforms a program written in the :ref:`xlang` language extension into a :ref:`purescala` program, then runs program verification.

• --noop

  Runs the program through the extraction and preprocessing phases, then outputs it in the specified directory. Used mostly for debugging purposes.

• --help

  Prints a helpful message, then exits.

Additional top-level options

These options are available by all Leon components:

• --debug=d1,d2,...

  Enables printing detailed messages for the components d1,d2,... . Available components are:

  • datagen (Data generators)
  • eval (Evaluators)
  • leon (The top-level component)
  • options (Options parsed by Leon)
  • repair (Program repair)
  • solver (SMT solvers and their wrappers)
  • synthesis (Program synthesis)
  • termination (Termination analysis)
  • timers (Timers, timer pools)
  • trees (Manipulation of trees)
  • verification (Verification)
  • xlang (Transformation of XLang into Pure Scala programs)

• --functions=f1,f2,...

  Only consider functions f1, f2, ... . This applies to all functionalities where Leon manipulates the input in a per-function basis.

• --solvers=s1,s2,...

  Use solvers s1, s2,... . If more than one solver is chosen, all chosen solvers will be used in parallel, and the best result will be presented. By default, the fairz3 solver is picked.

  Some solvers are specialized in proving verification conditions and will have hard time finding a counterexample in case of an invalid verification condition, whereas some are specialized in finding counterexamples, and some provide a compromise between the two. Also, some solvers do not as of now support higher-order functions.

  Available solvers include:

  • enum

    Uses enumeration-based techniques to discover counterexamples. This solver does not actually invoke an SMT solver, and operates entirely on the level of Leon trees.

  • fairz3

    Native Z3 with z3-templates for unfolding recursive functions (default).

  • smt-cvc4

    CVC4 through SMT-LIB. An algorithm within Leon takes up the unfolding of recursive functions, handling of lambdas etc. To use this or any of the following CVC4-based solvers, you need to have the cvc4 executable in your system path (the latest unstable version is recommended).

  • smt-cvc4-cex

    CVC4 through SMT-LIB, in-solver finite-model-finding, for counter-examples only. Currently, this solver does not handle higher-order functions.

  • smt-cvc4-proof

    CVC4 through SMT-LIB, for proofs only. Inductive reasoning happens within the solver, through use of the SMTLIB-2.5 standard. Currently, this solver does not handle higher-order functions.

  • smt-z3

    Z3 through SMT-LIB. To use this or the next solver, you need to have the z3 executable in your program path (the latest stable version is recommended). Inductive reasoning happens on the Leon side (similarly to smt-cvc4).

  • smt-z3-q

    Z3 through SMT-LIB, but (recursive) functions are encoded with universal quantification, and inductive reasoning happens within the solver. Currently, this solver does not handle higher-order functions.

  • unrollz3

    Native Z3, but inductive reasoning happens within Leon (similarly to smt-z3).

• --strict

  Terminate Leon after each phase if a non-fatal error is encountered (such as a failed verification condition). By default, this option is activated.

• --timeout=t

  Set a timeout for each attempt to prove one verification condition/ repair one function (in sec.)

Additional Options, by Component:

File Output

• --o=dir

  Output files to the directory dir (default: leon.out). Used when --noop is selected.

Code extraction

• --strictCompilation

  Do not try to recover after an error in compilation and exit Leon.

Synthesis

• --cegis:opttimeout

  Consider a time-out of CE-search as untrusted solution.

• --cegis:shrink

  Shrink non-det programs when tests pruning works well.

• --cegis:vanuatoo

  Generate inputs using new korat-style generator.

• --costmodel=cm

  Use a specific cost model for this search. Available: Naive, WeightedBranches

• --derivtrees

  Generate a derivation tree for every synthesized function. The trees will be output in *.dot files.

• --manual=cmd

  Override Leon's automated search through the space of programs during synthesis. Instead, the user can navigate the program space manually by choosing which deductive synthesis rules is instantiated each time.

  The optional cmd argument is a series of natural numbers in the form n1,n1,...,nk. It represents the series of command indexes that the search should instantiate at the beginning of the search. Useful for repeated search attempts.

Fair-z3 Solver

• --checkmodels

  Double-check counter-examples with evaluator.

• --codegen

  Use compiled evaluator instead of interpreter.

• --evalground

  Use evaluator on functions applied to ground arguments.

• --feelinglucky

  Use evaluator to find counter-examples early.

• --unrollcores

  Use unsat-cores to drive unrolling while remaining fair.

CVC4-solver

• --solver:cvc4=<cvc4-opt>

  Pass extra command-line arguments to CVC4.