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public version 1.01, February 16, 2016
* This version is based on private version 1.00 (see its CHANGES
below). The main difference is the new option "-backward-compat"
that allows to output Alt-Ergo's answers in an older syntax (<=
0.99.1). It is intended to be used with tools that do not support
the new 'slightly different' output format (e.g. option
-wp-alt-ergo-opt="-backward-compat" should be used with current
Frama-C versions).
private version 1.20, February 09, 2016
* default value of option -age-bound increased from 10 to 50
* bugfix when using option --all-models
* improvements in Matching: a set of instances may cause more than one
conflict. It's better to detect the more precise one
* remove case-split limit for the theory of arrays
* bugfix in the profiler plugin
* improvements in the default SAT solver
private version 1.10, October 19, 2015
* Improvements and bug fixes in the satML plugin
* Improvement of the solver of linear arithmetic in presence of
non-linear arithmetic parts in the equations to be solved
* Many improvements in case-split analysis. In particular, this is now
performed by explicit calls from the SAT solver. Its behavior can be
controlled with the new option "-case-split-policy". Possible values
for this option are: "after-theory-assume" (default),
"before-matching", and "after-matching".
* Alt-Ergo can now be called on zipped files (eg. <file> or
<file> Decompression is done on the fly with camlzip.
* Soundness bug fixes in arithmetic, interval calculus, union-find,
* Code reviewing/refactoring/rewriting/optimization in many parts of
the solver
private version 1.00, January 29, 2015
* General Improvements:
** theories data structures: semantic values (internal theories
representation of terms) are now hash-consed. This enables the
use of hash-based comparison (instead of structural comparison)
when possible
** theories combination: the dispatcher component, that sends
literals assumed by the SAT solver to different theories
depending on whether these literals are equalities,
disequalities or inequalities, has been re-implemented. The new
code is much simpler and enables new optimizations and
** case-split analysis: we made several improvements in the
heuristics of the case-split analysis mechanism over finite
** explanations propagation: we improved explanations propagation
in congruence closure and linear arithmetic algorithms. This
makes the proofs faster thanks to a better back-jumping in the
SAT solver part
** linear integer arithmetic: we re-implemented several parts of
linear arithmetic and introduced important improvements in the
Fourier-Motzkin algorithm to make it run on smaller sub-problems
avoiding some redundant executions. These optimizations allowed
a significant speed up on our internal benchmarks
** data structures: we optimized hash-consing and some functions in
the "formula" and "literal" modules
** SAT solving: we made a lot of improvements to the default
SAT-solver and to the SatML plugin. In particular, the decision
procedure part now receives facts (literals) in bulk from the
solvers, rather than individually, trimming the costs of
intermediate calls to theories reasoners, such as
** Matching: we extended the E-matching algorithm to also perform
matching modulo the theory of records. In addition, we
simplified matching heuristics and optimized the E-matching
process to avoid computing the same instances several times
** Memory management: thanks to the ocp-memprof tool
(, we identified some parts of
Alt-Ergo that needed some improvements in order to avoid useless
memory allocations, and thus unburden the OCaml garbage
** the function that retrieves the used axioms and predicates (when
option 'save-used-context' is set) has been improved
* Bug Fixes:
** 6 in the "inequalities" module of linear arithmetic
** 4 in the "formula" module
** 3 in the "ty" module used for types representation and
** 2 in the "theories front-end" module that interacts with the
SAT solvers
** 1 in the "congruence closure" algorithm
** 1 in "existential quantifiers elimination" module
** 1 in the "type-checker"
** 1 in the "AC theory" of associative and commutative function
** 1 in the "union-find" module
* New OCamlPro Plugins:
** profiling plugin: when activated, this plugin records and prints
some information about the current execution of Alt-Ergo every 'n'
seconds: In particular, one can observe a module being activated,
a function being called, the amount of time spent in every
module/function, the current decision/instantiation level, the
number of decisions/instantiations that have been made so far, the
number of case-splits, of boolean/theory conflicts, of assumptions
in the decision procedure, of generated instances per axiom, ...
** fm-simplex plugin: when activated, this plugin is used instead of
the Fourier-Motzkin method to infer bounds for linear integer
arithmetic affine forms (which are used in the case-split analysis
process). This module uses the Simplex algorithm to simulate
particular runs of Fourier-Motzkin. In practice, the new algorithm
scales better on linear integer arithmetic problems containing
lots of inequalities
* New Options:
-version-info: prints some information about this version of
Alt-Ergo (release and compilation dates, release commit ID)
-no-theory: deactivate theory reasoning. In this case, only the
SAT-solver and the matching parts are used
-inequalities-plugin: specify a plugin to use, instead of the
"default" Fourier-Motzkin algorithm, to handle inequalities of
linear arithmetic
-tighten-vars: when this option is set, the Fm-Simplex plugin will
try to infer bounds for integer variables as well. Note that this
option may be very expensive
-profiling-plugin: specify a profiling plugin to use to monitor an
execution of Alt-Ergo
-profiling <delay>: makes the profiling module prints its information
every <delay> seconds
-no-tcp: deactivate constraints propagation modulo theories
* Removed Capabilities:
** the pruning module used in the frontend is not available anymore
** the SMT and SMT2 front-ends have been removed. We plan to implement a
new front-end for SMT2 in upcoming releases
version 0.99.1, December 30, 2014
o the "SAT solving" part can now be delegated to an external plugin;
o new experimental SAT solver based on mini-SAT, provided as a
plugin. This solver is, in general, more efficient on ground
o heuristics simplification in the default SAT solver and in the
matching (instantiation) module;
o re-implementation of internal literals representation;
o improvement of theories combination architecture;
o rewriting some parts of the formulas module;
o bugfixes in records and numbers modules;
o new option "-no-Ematching" to perform matching without equality
reasoning (i.e. without considering "equivalence classes"). This
option is very useful for benchmarks coming from Atelier-B;
o two new experimental options: "-save-used-context" and
"-replay-used-context". When the goal is proved valid, the first option
allows to save the names of useful axioms into a ".used" file. The
second one is used to replay the proof using only the axioms listed
in the corresponding ".used" file. Note that the replay may fail
because of the absence of necessary ground terms generated by
useless axioms (that are not included in .used file) during the
initial run.
version 0.95.2, September 20th, 2013
o Alt-Ergo is now maintained and distributed by OCamlPro, while
academic research is conducted in partnership with the VALS team
o source code is reorganized into sub-directories,
o quantifiers instantiation heuristics are simplified,
o bug-fixes in matching, nums, records, sums,
o improvement of the GUI when opening big files.
version 0.95.1, March 05th, 2013
o bug fixes (existantial elimination, Euclidean division)
o minor enhancement (transformation of boolean equalities into equivalences)
o minor enhancement (sort axioms/definitions instances according to their size)
version 0.95, January 11th, 2013
+ Main changes in the solver:
o new combination method for Shostak solvers
o improvement of non-linear multiplication distribution over addition
o input language extension: polymorphic declaration are now allowed (logic x: 'a)
o input language extension: the types of terms can now be forced in a formula using the construct <term> : <type> (see man for an example)
o input language modification: a label should be a string. The construct <label> : <term> is replaced by "<label>" : <term>
o new keywords in the syntax: inversion, check, cut and include
o experimental options for theories models generation:
-model option: model on labeled terms
-complete-model option: complete model
o -timelimit n option: set the time limit to n seconds (not supported on Windows)
o bug fixes
+ Main changes in the graphical interface:
o the number of instances for each axiom are now shown on the right of the GUI
o the number of instances of each axiom can be limited by the user
o the modifications made in the GUI can now be saved in a session file <f>.agr
o session files can be replayed with -replay option
o models can be displayed in the GUI
o unsat-cores (-proof option) can be used to simplify the context
version 0.94, December 2nd, 2011
o the theory of records replaces the theory of pairs
o bug fixes
(intervals, term data-structure, stack-overflows, matching,
existentials, distincts, CC, GUI)
o improvements
(SMT-Lib2 front-end, intervals, case-splits,
triggers, lets)
o multiset ordering for AC(X)
o manual lemma instantiation in the GUI
version 0.93.1, May 9th, 2011
o bug fixes (distinct, let-in, explanations)
version 0.93, April 12th, 2011
o -steps <i> stops Alt-Ergo after a given number of steps
o -max-split option to limit the number of case-splits
o new polymorphic theory of arrays: ('a, 'b) farray
o explanations (-proof option)
o Built-in support for enumeration types
o graphical frontend (altgr-ergo), needs to be compiled with make
gui && make install-gui
o new predicate distinct (a,b,c, ...) to express that constants
a,b,c,... are pairwise distinct
o new constructs: let x = <term> in <term>
let x = <term> in <formula>
o partial support for / (division) operator
o bug fixes
version 0.92.2, October 22nd, 2010
o New built-in syntax for the theory of arrays
o Fixes a bug in the arithmetic module
o Allows folding and unfolding of predicate definitions
o Fixes other bugs
version 0.91, May 19th, 2010
o experimental support for the theory of functional polymorphic
arrays with the -arrays option
o the -pairs option should now be used for the built-in support of
polymorphic pairs
o support the equality part of the omega test with the -omega option
o partial support for non-linear arithmetics
o support case split on integer variables
o new support for Euclidean division and modulo operators
o new environment variable ERGOLIB to specify the library directory
version 0.9, July 17th, 2009
o support AC symbols
o support for C-like hexadecimal floating-point constants
o handle the division operator
version 0.8, July 21st, 2008
o pretty output with the -color option
o the SAT solver part is now equipped with a backjumping mechanism
o now handles the flet and let SMT-lib constructs
o goal directed strategy
o pruning strategy (-select option)
o incremental strategy for instantiation of lemmas
o fail if a parameter is bound twice in a definition
o treatment of existential formulas have been slightly improved
o decision procedure for polymorphic pairs
o decision procedure for bit-vectors
o combination scheme for several decision procedures
version 0.7.3, March 5th, 2008
o renamings in the interfaces
o provides an API for alt-ergo (make api or make api.byte)
o handles the modulo operator (%) as an uninterpreted symbol
o allow labels on any term, not only on predicates
version 0.7, October 11th, 2007
o trigger construction has been improved
o preliminary implementation of combination scheme (Arithmetic+pairs)
o the SAT loop has been improved
version 0.6, February 1st, 2007
o new CC(X) architecture (it can know directly handle relation symbols)
o fully handles the polymorphism of the logic
version 0.5, October 12th, 2006
o first (beta) release
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