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version 2.0.0free, February 13, 2019
=====================================
* same as 2.0.0, except that "OCamlPro NonCommercial Purpose License"
is replaced with "Apache Software License version 2.0"
version 2.0.0, November 14, 2017
================================
* integration of floatingpoint arithmetic reasoning: this is done via
the support of the rounding operator as done in the Gappa tool. FPA
reasoning can be enabled by calling AltErgo as follows:
altergo usefpa prelude fpatheory2017010416h00.why file.why
where fpatheory2017010416h00.why is a prelude distributed with
AltErgo. More details about the integration are given in this
paper: https://hal.inria.fr/hal01522770, and dditional benchmarks
can be found here:
https://gitlab.com/OCamlProIguernlala/ThreeTierFPABenchs
* a new lightweight reasoning step before SAT solving that enables a
kind of backward reasoning/goal unfolding (can be disabled with
option nobackward)
* integration of a simple cache mechanism for unit facts in the SAT
(learnt clauses, assumed facts, instances, theory deductions, ...)
to improve BCP (can be disabled with option nosatlearning)
* the code of the profiler is now integrated in AltErgo and is
statically linked
* deep code refactoring. In particular, one can easily build an
AltErgo library or define/register a new parser
* add the ability to parse preludes with prelude <prelude_1.why> ...
prelude <prelude_n.why>
* add the ability to disable weak pointers in hashconsing module
using option disableweaks (useful for more determinism)
* GUI: goals are now shown in positive form
* bugfix related to timelimit option (use of ITIMER_VIRTUAL instead
of ITIMER_REAL except for the GUI)
* bugfix in UF related to normalization of terms in presence of AC
symbols
* new options nodecisions and nofm to disable decisions in the SAT
and the FourierMotzkin algorithm, respectively
* new improvements and heuristics in the SAT, terms, formulas,
congruence closure, profiler, ...
* update licensing: most files are now licensed under the terms of the
Apache license v2. Some recent OCamlPro additions are licensed under
the terms of the OCamlPro NonCommercial Purpose License v1
version 1.30, November 21, 2016
==============================
* experimental support for models generation (for more details, see
http://www.ocamlpro.com/2016/11/21/releaseofaltergo130withexperimentalsupportformodelsgeneration/).
* simplify formulas of the form "forall x : t. x <> t or F" when t
does not contain x. The only relevant instance in this case is
"(x <> t or F) {x > t}". In a similar way, this allows to simplify
formulas of the form "exists x : t. x = t and F" to "F {x > t}".
* integration of general simplex in IntervalCalculus based on
ocplibsimplex.
* important parts of Intervals and IntervalCalculus have been
rewritten and improved.
* improve tightening of intervals for nonlinear variables, and of the
CPlike loop.
* extend FourierMotzkin to deduce more bounds based on relational
dependencies of the form "c * x <= (Sum_i d_i * y_i) + e"
* various improvements in the default SAT solver, Term, Formula,
IntervalCalculus, Matching, Numbers, casesplit, ...
* various (soundness and/or completeness) bug fixes in Uf, Intervals,
IntervalCalculus, Theory, Formula, typechecking, Triggers,
fmsimplex and satML, ...
* new option "instafterbj" that forces an instantiation round after
each backtracking/backjumping in the default SAT solver.
* new option "nobackjumping" that disables backjumping in the
default SAT solver (for debugging).
* new option "fmcrosslimit" that controls the number of
intermediate inequalities produces by FourierMotzking. Default
value is 10,000.
* new option "noac" to be able to deactivate the AC theory
* new option "noNLA" that disables nonlinear arithmetic reasoning
(*, /, %). Nonlinear multiplication remains AC.
version 1.20, February 09, 2016
==============================
* default value of option agebound increased from 10 to 50
* bugfix when using option allmodels
* improvements in Matching: a set of instances may cause more than one
conflict. It's better to detect the more precise one
* remove casesplit limit for the theory of arrays
* bugfix in the profiler plugin
* improvements in the default SAT solver
version 1.10, October 19, 2015
==============================
* Improvements and bug fixes in the satML plugin
* Improvement of the solver of linear arithmetic in presence of
nonlinear arithmetic parts in the equations to be solved
* Many improvements in casesplit analysis. In particular, this is now
performed by explicit calls from the SAT solver. Its behavior can be
controlled with the new option "casesplitpolicy". Possible values
for this option are: "aftertheoryassume" (default),
"beforematching", and "aftermatching".
* AltErgo can now be called on zipped files (eg. <file>.mlw.zip or
<file>.why.zip). Decompression is done on the fly with camlzip.
* Soundness bug fixes in arithmetic, interval calculus, unionfind,
...
* Code reviewing/refactoring/rewriting/optimization in many parts of
the solver
version 1.00, January 29, 2015
==============================
* General Improvements:
** theories data structures: semantic values (internal theories
representation of terms) are now hashconsed. This enables the
use of hashbased 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 reimplemented. The new
code is much simpler and enables new optimizations and
factorizations
** casesplit analysis: we made several improvements in the
heuristics of the casesplit analysis mechanism over finite
domains
** explanations propagation: we improved explanations propagation
in congruence closure and linear arithmetic algorithms. This
makes the proofs faster thanks to a better backjumping in the
SAT solver part
** linear integer arithmetic: we reimplemented several parts of
linear arithmetic and introduced important improvements in the
FourierMotzkin algorithm to make it run on smaller subproblems
avoiding some redundant executions. These optimizations allowed
a significant speed up on our internal benchmarks
** data structures: we optimized hashconsing and some functions in
the "formula" and "literal" modules
** SAT solving: we made a lot of improvements to the default
SATsolver 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
FourierMotzkin
** Matching: we extended the Ematching algorithm to also perform
matching modulo the theory of records. In addition, we
simplified matching heuristics and optimized the Ematching
process to avoid computing the same instances several times
** Memory management: thanks to the ocpmemprof tool
(http://memprof.typerex.org/), we identified some parts of
AltErgo that needed some improvements in order to avoid useless
memory allocations, and thus unburden the OCaml garbage
collector
** the function that retrieves the used axioms and predicates (when
option 'saveusedcontext' 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
manipulation
** 2 in the "theories frontend" module that interacts with the
SAT solvers
** 1 in the "congruence closure" algorithm
** 1 in "existential quantifiers elimination" module
** 1 in the "typechecker"
** 1 in the "AC theory" of associative and commutative function
symbols
** 1 in the "unionfind" module
* New OCamlPro Plugins:
** profiling plugin: when activated, this plugin records and prints
some information about the current execution of AltErgo 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 casesplits, of boolean/theory conflicts, of assumptions
in the decision procedure, of generated instances per axiom, ...
** fmsimplex plugin: when activated, this plugin is used instead of
the FourierMotzkin method to infer bounds for linear integer
arithmetic affine forms (which are used in the casesplit analysis
process). This module uses the Simplex algorithm to simulate
particular runs of FourierMotzkin. In practice, the new algorithm
scales better on linear integer arithmetic problems containing
lots of inequalities
* New Options:
versioninfo: prints some information about this version of
AltErgo (release and compilation dates, release commit ID)
notheory: deactivate theory reasoning. In this case, only the
SATsolver and the matching parts are used
inequalitiesplugin: specify a plugin to use, instead of the
"default" FourierMotzkin algorithm, to handle inequalities of
linear arithmetic
tightenvars: when this option is set, the FmSimplex plugin will
try to infer bounds for integer variables as well. Note that this
option may be very expensive
profilingplugin: specify a profiling plugin to use to monitor an
execution of AltErgo
profiling <delay>: makes the profiling module prints its information
every <delay> seconds
notcp: deactivate constraints propagation modulo theories
* Removed Capabilities:
** the pruning module used in the frontend is not available anymore
** the SMT and SMT2 frontends have been removed. We plan to implement a
new frontend 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 miniSAT, provided as a
plugin. This solver is, in general, more efficient on ground
problems;
o heuristics simplification in the default SAT solver and in the
matching (instantiation) module;
o reimplementation 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 "noEmatching" to perform matching without equality
reasoning (i.e. without considering "equivalence classes"). This
option is very useful for benchmarks coming from AtelierB;
o two new experimental options: "saveusedcontext" and
"replayusedcontext". 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 AltErgo is now maintained and distributed by OCamlPro, while
academic research is conducted in partnership with the VALS team
(LRI),
o source code is reorganized into subdirectories,
o quantifiers instantiation heuristics are simplified,
o bugfixes 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 nonlinear 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
completemodel 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 unsatcores (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 datastructure, stackoverflows, matching,
existentials, distincts, CC, GUI)
o improvements
(SMTLib2 frontend, intervals, casesplits,
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, letin, explanations)
version 0.93, April 12th, 2011
=================================
o steps <i> stops AltErgo after a given number of steps
o maxsplit option to limit the number of casesplits
o new polymorphic theory of arrays: ('a, 'b) farray
o explanations (proof option)
o Builtin support for enumeration types
o graphical frontend (altgrergo), needs to be compiled with make
gui && make installgui
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 builtin 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 builtin support of
polymorphic pairs
o support the equality part of the omega test with the omega option
o partial support for nonlinear 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 Clike hexadecimal floatingpoint 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 SMTlib 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 bitvectors
o combination scheme for several decision procedures
version 0.7.3, March 5th, 2008
===============================
o renamings in the interfaces
o provides an API for altergo (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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