NEWS.md

   1 This file contains a summary of important user-visible changes.
   2
   3 cvc5 1.0
   4 =========
   5
   6 **Website**: https://cvc5.github.io
   7
   8 **Documentation**: https://cvc5.github.io/docs
   9
  10 **System Description**
  11   * *cvc5: A Versatile and Industrial-Strength SMT Solver.*
  12     Barbosa H., Barrett C., Brain M., Kremer G., Lachnitt H.,
  13     Mann M., Mohamed A., Mohamed M., Niemetz A., Nötzli A.,
  14     Ozdemir A., Preiner M., Reynolds A., Sheng Y., Tinelli C., and Zohar Y.,
  15     TACAS 2022.
  16
  17 **New Features**
  18
  19 * *Streamlined C++ API*
  20   - Documentation: https://cvc5.github.io/docs/latest/api/cpp/cpp.html
  21
  22 * *Two new Python language bindings*
  23   - Base module: Feature complete with C++ API
  24   - Pythonic module: A pythonic wrapper around the base module
  25   - Documentation: https://cvc5.github.io/docs/latest/api/python/python.html
  26
  27 * *New Java language bindings*
  28   - Documentation: https://cvc5.github.io/docs/latest/api/java/java.html
  29
  30 * *Theory of Bags (Multisets)*
  31   - A new theory of bags, which are collections that allow duplicates. It
  32     supports basic operators like union disjoint, union max, intersection,
  33     difference subtract, difference remove, duplicate removal, and multiplicity
  34     of an element in a bag.
  35
  36 * *Theory of Sequences*
  37   - A new parametric theory of sequences whose syntax is compatible with the
  38     syntax for sequences used by Z3.
  39   - A new array-inspired procedure (option `--seq-array`).
  40
  41 * *Arithmetic*
  42   - Nonlinear real arithmetic is now solved using a new solver based on
  43     cylindrical algebraic coverings. Includes full support for non-rational
  44     models and a number of options `--nl-cov-*` for, e.g., different projection
  45     operators, Lazard's lifting or variable elimination.
  46     The new solver requires the libpoly library, and Lazard's lifting
  47     additionally requires CoCoALib.
  48
  49 * *Arrays*
  50   - Added support for an `eqrange` predicate. `(eqrange a b i j)` is true
  51     if arrays `a` and `b` are equal on all indices within indices `i` and `j`.
  52
  53 * *Bit-vectors*
  54   - New bit-vector solver with CaDiCaL as default SAT back-end.
  55   - New approach for solving bit-vectors as integers (option `--solve-bv-as-int`).
  56
  57 * *Datatypes*
  58   - Support for generic datatype updaters `((_ update s) t u)` which replaces
  59     the field specified by selector `s` of `t` by the value `u`.
  60
  61 * *Integers*
  62   - Support for an integer operator `(_ iand n)` that returns the bitwise `and`
  63     of two integers, seen as integers modulo n.
  64   - Support for an integer operator `int.pow2`, used as `(int.pow2 x)` which
  65     represents 2 to the power of x.
  66
  67 * *Quantifiers*
  68   - Improved support for enumerative instantiation (option `--enum-inst`).
  69   - SyGuS-based quantifier instantiation (option `--sygus-inst`).
  70
  71 * *Strings*
  72   - Improved performance using new techniques, including model-based
  73     reductions, eager context-dependent simplification, and equality-based
  74     conflict finding.
  75   - Support for `str.indexof_re(s, r, n)`, which returns the index of the first
  76     occurrence of a regular expression `r` in a string `s` after index `n` or
  77     -1 if `r` does not match a substring after `n`.
  78
  79 * *Proofs*
  80   * Documentation available at:
  81     https://cvc5.github.io/docs/latest/proofs/proofs.html
  82   * When used after an unsatisfiable response to `checkSat`, `getProof`
  83     returns a representation of the refutation proof for the current set of
  84     assertions (get-proof in SMT-LIB).
  85   * Preliminary support for translations to external proof formats LFSC and Alethe.
  86
  87 * *Difficulty Estimation*
  88   - The API method `getDifficulty` returns a map from asserted formulas to
  89     integers which estimates how much that formula contributed to the
  90     difficulty of the overall problem (get-difficulty in SMT-LIB).
  91
  92 * *Learned Literals*
  93   - The API method `getLearnedLiterals` gets a list of literals that are
  94     entailed by the current set of assertions that were learned during solving
  95     (get-learned-literals in SMT-LIB).
  96
  97 * *Abduction and Interpolation*
  98   * The API method `getAbduct` can be used to find an abduct for the current set
  99     of assertions and provided goal (get-abduct in SMT-LIB). Optionally, a
 100     SyGuS grammar can be provided to restrict the shape of possible abducts.
 101     If using the text inferace, the grammar may be provided using the same
 102     syntax for grammars as in SyGuS IF format.
 103   * The API method `getInterpolant` can be used to find an interpolant for the
 104     current set of assertions and provided goal (get-interpolant in SMT-LIB).
 105     Like abduction, grammars may be provided to restrict the shape of
 106     interpolants.
 107
 108 * *Support for Incremental Synthesis Queries*
 109   - The core SyGuS solver now supports getting multiple solutions for a
 110     synthesis conjecture via the API. The method `checkSynthNext` finds the
 111     next SyGuS solution to the current set of SyGuS constraints
 112     (check-synth-next in SyGuS IF).
 113   - `getAbductNext` finds the next abduct for the current set of
 114     assertions and provided goal (get-abduct-next in SMT-LIB).
 115   - `getInterpolantNext` finds the next interpolant for the current set of
 116     assertions and provided goal (get-interpolant-next in SMT-LIB).
 117
 118 * *Pool-based Quantifier Instantiation*
 119   - The API method `declarePool` declares symbol sets of terms called pools
 120     (`declare-pool` in SMT-LIB).
 121   - Pools can be used in annotations of quantified formulas for fine grained
 122     control over quantifier instantiations (:inst-pool, :inst-add-to-pool,
 123     :skolem-add-to-pool in SMT-LIB).
 124
 125 * Diagnostic Outputs
 126   - The option `-o TAG` can be used to enable a class of useful diagnostic
 127     information, such as the state of the input formula before and after
 128     pre-preprocessing, quantifier instantiations, literals learned
 129     during solving, among others. For SyGuS problems, it can be used to
 130     show candidate solutions and grammars that the solver has generated.
 131
 132 * *Unsat cores*
 133   - Production modes based on the new proof infrastructure
 134     (`--unsat-cores-mode=sat-proof`) and on the solving-under-assumption
 135     feature of Minisat (`--unsat-cores-mode=assumptions`). The mode based on
 136     SAT assumptions + preprocessing proofs is the new default.
 137   - Computing minimal unsat cores (option `--minimal-unsat-cores`).
 138
 139 * *Blocking Models*
 140   - The API method `blockModels` can be used to block the current model using
 141     various policies for how to exclude the values of terms (`block-model` in
 142     SMT-LIB).
 143   - The API method `blockModelValues` can be used to block the current model
 144     for a provided set of terms (`block-model-values` in SMT-LIB).
 145
 146 * *Model Cores*
 147   - The API method `isModelCoreSymbol` can be used to query whether the value
 148     for a symbol was critical to whether the model satisfies the current set of
 149     assertions.
 150   - Models can be limited to show only model core symbols (option `--model-cores`).
 151
 152 **Changes**
 153
 154 * CaDiCaL and SymFPU are now required dependencies. CaDiCaL 1.4.1 is now the
 155   version used by default.
 156 * Options have been extensively refactored, please refer to the cvc5
 157   documentation for further information.
 158 * Removed support for the CVC language.
 159 * SyGuS: Removed support for SyGuS-IF 1.0.
 160 * Removed support for the (non-standard) `define` command.
 161 * Removed the legacy API along with the Java and Python bindings for it.
 162 * Interactive shell: the GPL-licensed Readline library has been replaced the
 163   BSD-licensed Editline. Compiling with `--best` now enables Editline, instead
 164   of Readline. Without selecting optional GPL components, Editline-enabled CVC4
 165   builds will be BSD licensed.
 166 * The `competition` build type includes the dependencies used for SMT-COMP by
 167   default. Note that this makes this build type produce GPL-licensed binaries.
 168 * Bit-vector operator `bvxnor` was previously mistakenly marked as
 169   left-assoicative in SMT-LIB. This has recently been corrected in SMT-LIB. We
 170   now restrict `bvxnor` to only allow two operands in order to avoid confusion
 171   about the semantics, since the behavior of n-ary operands to `bvxnor` is now
 172   undefined in SMT-LIB.
 173 * SMT-LIB output for `get-model` command now conforms with the standard,
 174   and does *not* begin with the keyword `model`. The output
 175   is the same as before, only with this word removed from the beginning.
 176 * Building with Python 2 is now deprecated.
 177 * The SMT-LIB syntax for some extensions has been changed. Notably, set
 178   operators are now prefixed by `set.`, and relations by `rel.`. For example,
 179   `union` is now written `set.union`.
 180 * Removed support for redundant logics `ALL_SUPPORTED` and `QF_ALL_SUPPORTED`,
 181   use `ALL` and `QF_ALL` instead.