NEWS

   1 This file contains a summary of important user-visible changes.
   2
   3 Changes since 1.8
   4 =================
   5
   6 New Features:
   7 * A new parametric theory of sequences whose syntax is compatible with the
   8   syntax for sequences used by Z3.
   9 * Arrays: Added support for an `eqrange` predicate. `(eqrange a b i j)` is true
  10   if arrays `a` and `b` are equal on all indices within indices `i` and `j`.
  11 * Support for an integer operator `(_ iand n)` that returns the bitwise `and`
  12   of two integers, seen as integers modulo n.
  13
  14 Improvements:
  15 * New API: Added functions to retrieve the heap/nil term when using separation
  16   logic.
  17
  18 Changes:
  19 * SyGuS: Removed support for SyGuS-IF 1.0.
  20 * Removed Java and Python bindings for the legacy API
  21 * Interactive shell: the GPL-licensed Readline library has been replaced the
  22   BSD-licensed Editline. Compiling with `--best` now enables Editline, instead
  23   of Readline. Without selecting optional GPL components, Editline-enabled CVC4
  24   builds will be BSD licensed.
  25 * The `competition` build type includes the dependencies used for SMT-COMP by
  26   default. Note that this makes this build type produce GPL-licensed binaries.
  27
  28 Changes since 1.7
  29 =================
  30
  31 New Features:
  32 * New C++ and Python API: CVC4 has a new, more streamlined API. We plan to
  33   make CVC4 1.8 the last version that ships with the legacy API.
  34 * Strings: Full support of the new SMT-LIB standard for the theory of strings,
  35   including:
  36   * Support for `str.replace_re`, `str.replace_re_all`, `str.is_digit`,
  37     `str.from_code`, `re.diff`, and `re.comp`
  38   * Support for new operator names (e.g. `str.in_re` instead of `str.in.re`),
  39     new escape sequences. The new syntax is enabled by default for smt2 files.
  40 * Support for syntax-guided synthesis (SyGuS) problems in the new API. C++
  41   examples of the SyGuS API can be found in `./examples/api/sygus_*.cpp`.
  42 * Support for higher-order constraints. This includes treating function sorts
  43   (constructible by `->`) as first-class sorts and handling partially applied
  44   function symbols. Support for higher-order constraints can be enabled by
  45   the option `--uf-ho`.
  46 * Support for set comprehension binders `comprehension`.
  47 * Eager bit-blasting: Support for SAT solver Kissat.
  48
  49 Improvements:
  50 * API: Function definitions can now be requested to be global. If the `global`
  51   parameter is set to true, they persist after popping the user context.
  52 * Java/Python bindings: The bindings now allow users to catch exceptions
  53 * Arithmetic: Performance improvements
  54   * Linear solver: New lemmas inspired by unit-cube tests
  55   * Non-linear solver: Expanded set of axioms
  56 * Ackermannization: The Ackermannization preprocessing pass now supports
  57   uninterpreted sorts and as a result all QF_UFBV problems are supported in
  58   combination with eager bit blasting.
  59
  60 Changes:
  61 * CVC language: Models printed in the CVC language now include an explicit end
  62   marker to facilitate the communication over pipes with CVC4.
  63 * API change: `SmtEngine::query()` has been renamed to
  64   `SmtEngine::checkEntailed()` and `Result::Validity` has been renamed to
  65   `Result::Entailment` along with corresponding changes to the enum values.
  66 * Java API change: The name of CVC4's package is now `edu.stanford.CVC4`
  67   instead of `edu.nyu.acsys.CVC4`.
  68 * The default output language is changed from CVC to SMT-LIB 2.6. The
  69   default output language is used when the problem language cannot be
  70   easily inferred (for example when CVC4 is used from the API).
  71 * Printing of BV constants: previously CVC4 would print BV constant
  72   values as indexed symbols by default and in binary notation with the
  73   option --bv-print-consts-in-binary. To be SMT-LIB compliant the
  74   default behavior is now to print BV constant values in binary
  75   notation and as indexed symbols with the new option
  76   --bv-print-consts-as-indexed-symbols. The option
  77   --bv-print-consts-in-binary has been removed.
  78 * Updated to SyGuS language version 2.0 by default. This is the last release
  79   that will support the SyGuS language version 1.0 (`--lang=sygus1`). A
  80   script is provided to convert version 1.0 files to version 2.0, see
  81   `./contrib/sygus-v1-to-v2.sh`.
  82 * Support for user-provided rewrite rule quantifiers have been removed.
  83 * Support for certain option aliases have been removed.
  84 * Support for parallel portfolio builds has been removed.
  85
  86 Changes since 1.6
  87 =================
  88
  89 New Features:
  90 * Proofs:
  91   * Support for bit-vector proofs with eager bitblasting (older versions only
  92     supported proofs with lazy bitblasting).
  93 * Strings:
  94   * Support for `str.replaceall` operator.
  95   * New option `--re-elim` to reduce regular expressions to extended string
  96     operators, resulting in better performance on regular expression benchmarks
  97     (enabled by default).
  98 * SyGuS:
  99   * Support for abduction (`--sygus-abduct`). Given a formula, this option uses
 100     CVC4's SyGuS solver to find a sufficient condition such that the
 101     conjunction of the condition and the formula is unsatisfiable.
 102   * Support for two new term enumerator strategies: variable agnostic
 103     (`--sygus-active-gen=var-agnostic`) and fast (`--sygus-active-gen=enum`).
 104     By default, CVC4 tries to choose the best term enumerator strategy
 105     automatically based on the input (`--sygus-active-gen=auto`).
 106   * Support for streaming solutions of increasingly smaller size when using the
 107     PBE solver (`--sygus-stream --sygus-pbe`). After the first solution is found
 108     and printed, the solver will continue to look for new solutions and print
 109     those, if any, that are smaller than previously printed solutions.
 110   * Support for unification-based techniques in non-separable specifications
 111     (`--sygus-unif`). For solving invariant problems a dedicate mode
 112     (`--sygus-unif-boolean-heuristic-dt`) is available that builds candidate
 113     solutions using heuristic decision tree learning.
 114
 115 Improvements:
 116 * Strings:
 117   * Significantly better performance on string benchmarks over the core theory
 118     and those with extended string functions like substring, contains, and
 119     replace.
 120
 121 Changes:
 122 * API change: Expr::iffExpr() is renamed to Expr::eqExpr() to reflect its
 123               actual behavior.
 124 * Compiling the language bindings now requires SWIG 3 instead of SWIG 2.
 125 * The CVC3 compatibility layer has been removed.
 126 * The build system now uses CMake instead of Autotools. Please refer to
 127   [INSTALL.md](https://github.com/CVC4/CVC4/blob/master/INSTALL.md) for
 128   up-to-date instructions on how to build CVC4.
 129
 130 Changes since 1.5
 131 =================
 132
 133 New Features:
 134 * A new theory of floating points.
 135 * Novel approach for solving quantified bit-vectors (BV).
 136 * Eager bit-blasting: Support for SAT solver CaDiCaL.
 137 * A new Gaussian Elimination preprocessing pass for the theory of bit-vectors.
 138 * Support for transcendental functions (sin, cos, exp). In SMT2 input, this
 139   can be enabled by adding T to the logic (e.g., QF_NRAT).
 140 * Support for new operators in strings, including string inequality (str.<=)
 141   and string code (str.code).
 142 * Support for automated rewrite rule generation from sygus (*.sy) inputs using
 143   syntax-guided enumeration (option --sygus-rr).
 144
 145 Improvements:
 146 * Incremental unsat core support.
 147 * Further development of rewrite rules for the theory of strings and regular
 148   expressions.
 149 * Many optimizations for syntax-guided synthesis, including improved symmetry
 150   breaking for enumerative search and specialized algorithms for
 151   programming-by-examples conjectures.
 152
 153 Changes:
 154 * Eager bit-blasting: Removed support for SAT solver CryptoMinisat 4, added
 155   support for CryptoMinisat 5.
 156 * The LFSC proof checker now resides in its own repository on GitHub at
 157   https://github.com/CVC4/LFSC. It is not distributed with CVC4 anymore.
 158
 159 Changes since 1.4
 160 =================
 161
 162 * Improved heuristics for reasoning about non-linear arithmetic.
 163 * Native support for syntax-guided synthesis (sygus).
 164 * Support for many new heuristics for reasoning with quantifiers, including
 165   finite model finding.
 166 * Support for proofs for uninterpreted functions, arrays, bitvectors, and
 167   their combinations.
 168 * Performance improvements to existing theories.
 169 * A new theory of sets with cardinality and relations.
 170 * A new theory of strings.
 171 * Support for unsat cores.
 172 * Support for separation logic constraints.
 173 * Simplification mode "incremental" no longer supported.
 174 * Support for array constants in constraints.
 175 * Syntax for array models has changed in some language front-ends.
 176 * New input/output languages supported: "smt2.0" and "smtlib2.0" to
 177   force SMT-LIB v2.0; "smt2.5" and "smtlib2.5" to force SMT-LIB v2.5;
 178   "smt2.6" and "smtlib2.6" to force SMT-LIB v2.6;
 179   "smt", "smtlib", "smt2", and "smtlib2" all refer to the current standard
 180   version 2.6.  If an :smt-lib-version is set in the input, that overrides
 181   the command line.
 182 * Abstract values in SMT-LIB models are now ascribed types (with "as").
 183 * In SMT-LIB model output, real-sorted but integer-valued constants are
 184   now printed in accordance with the standard (e.g. "1.0").
 185
 186 Changes since 1.3
 187 =================
 188
 189 * CVC4 now supports libc++ in addition to libstdc++ (this especially
 190   helps on Mac OS Mavericks).
 191 * The LFSC proof checker has been incorporated into CVC4 sources.
 192 * Theory of finite sets, handling the MLSS fragment (singleton, union,
 193   intersection, set subtraction, membership and subset).
 194 * By default, CVC4 builds in "production" mode (optimized, with fewer
 195   internal checks on).  The common alternative is a "debug" build, which
 196   is much slower.  By default, CVC4 builds with no GPL'ed dependences.
 197   However, this is not the best-performing version; for that, you should
 198   configure with "--enable-gpl --best", which links against GPL'ed
 199   libraries that improve usability and performance.  For details on
 200   licensing and dependences, see the README file.
 201 * Small API adjustments to Datatypes to even out the API and make it
 202   function better in Java.
 203 * Timed statistics are now properly updated even on process abort.
 204 * Better automatic handling of output language setting when using CVC4
 205   via API.  Previously, the "automatic" language setting was sometimes
 206   (though not always) defaulting to the internal "AST" language; it
 207   should now (correctly) default to the same as the input language
 208   (if the input language is supported as an output language), or the
 209   "CVC4" native output language if no input language setting is applied.
 210 * The SmtEngine cannot be safely copied with the copy constructor.
 211   Previous versions inadvertently permitted clients to do this via the
 212   API.  This has been corrected, copy and assignment of the SmtEngine
 213   is no longer permitted.
 214
 215 Changes since 1.2
 216 =================
 217
 218 New features:
 219 * SMT-LIB-compliant support for abs, to_real, to_int, is_int, which were
 220   previously missing
 221 * New bv2nat/int2bv operators for bitvector/integer inter-compatibility.
 222 * Support in linear logics for /, div, and mod by constants (with the
 223   --rewrite-divk command line option).
 224 * Parsing support for TPTP's TFF and TFA formats.
 225 * A new theory of strings: word (dis-)equations, length constraints,
 226   regular expressions.
 227 * Increased compliance to SMT-LIBv2, numerous bugs and usability issues
 228   resolved.
 229 * New :command-verbosity SMT option to silence success and error messages
 230   on a per-command basis, and API changes to Command infrastructure to
 231   support this.
 232
 233 Behavioral changes:
 234 * It is no longer permitted to request model or proof generation if there's
 235   been an intervening push/pop.
 236 * User-defined symbols (define-funs) are no longer reported in the output
 237   of get-model commands.
 238 * Exit codes are now more standard for UNIX command-line tools.  Exit code
 239   zero means no error---but the result could be sat, unsat, or unknown---and
 240   nonzero means error.
 241
 242 API changes:
 243 * Expr::substitute() now capable of substituting operators (e.g.,
 244   function symbols under an APPLY_UF)
 245 * Numerous improvements to the Java language bindings
 246
 247 Changes since 1.1
 248 =================
 249
 250 * Real arithmetic now has three simplex solvers for exact precision linear
 251   arithmetic: the classical dual solver and two new solvers based on
 252   techniques for minimizing the sum of infeasibilities. GLPK can now be used
 253   as a heuristic backup to the exact precision solvers.  GLPK must be enabled
 254   at configure time. See --help for more information on enabling these solvers.
 255 * added support for "bit0" and "bit1" bitvector constants in SMT-LIB v1.2
 256 * support for theory "alternates": new ability to prototype new decision
 257   procedures that are selectable at runtime
 258 * various bugfixes
 259
 260 Changes since 1.0
 261 =================
 262
 263 * bit-vector solver now has a specialized decision procedure for unsigned bit-
 264   vector inequalities
 265 * numerous important bug fixes, performance improvements, and usability
 266   improvements
 267 * support for multiline input in interactive mode
 268 * Win32-building support via mingw
 269 * SMT-LIB get-model output now is easier to machine-parse: contains (model...)
 270 * user patterns for quantifier instantiation are now supported in the
 271   SMT-LIBv1.2 parser
 272 * --finite-model-find was incomplete when using --incremental, now fixed
 273 * the E-matching procedure is slightly improved
 274 * Boolean terms are now supported in datatypes
 275 * tuple and record support have been added to the compatibility library
 276 * driver verbosity change: for printing all commands as they're executed, you
 277   now need verbosity level >= 3 (e.g., -vvv) instead of level 1 (-v).  This
 278   allows tracing the solver's activities (with -v and -vv) without having too
 279   much output.
 280 * to make CVC4 quieter in abnormal (e.g., "warning" conditions), you can
 281   use -q.  Previously, this would silence all output (including "sat" or
 282   "unsat") as well.  Now, single -q silences messages and warnings, and
 283   double -qq silences all output (except on exception or signal).