NEWS

   1 This file contains a summary of important user-visible changes.
   2
   3 Changes since 1.6
   4 =================
   5
   6 New Features:
   7 * Proofs:
   8   * Support for bit-vector proofs with eager bitblasting (older versions only
   9     supported proofs with lazy bitblasting).
  10 * Strings:
  11   * Support for `str.replaceall` operator.
  12   * New option `--re-elim` to reduce regular expressions to extended string
  13     operators, resulting in better performance on regular expression benchmarks
  14     (enabled by default).
  15 * SyGuS:
  16   * Support for abduction (`--sygus-abduct`). Given a formula, this option uses
  17     CVC4's SyGuS solver to find a sufficient condition such that the
  18     conjunction of the condition and the formula is unsatisfiable.
  19   * Support for two new term enumerator strategies: variable agnostic
  20     (`--sygus-active-gen=var-agnostic`) and fast (`--sygus-active-gen=enum`).
  21     By default, CVC4 tries to choose the best term enumerator strategy
  22     automatically based on the input (`--sygus-active-gen=auto`).
  23
  24 Improvements:
  25 * Strings:
  26   * Significantly better performance on string benchmarks over the core theory
  27     and those with extended string functions like substring, contains, and
  28     replace.
  29
  30 Changes:
  31 * API change: Expr::iffExpr() is renamed to Expr::eqExpr() to reflect its
  32               actual behavior.
  33 * Compiling the language bindings now requires SWIG 3 instead of SWIG 2.
  34 * The CVC3 compatibility layer has been removed.
  35 * The build system now uses CMake instead of Autotools. Please refer to
  36   [INSTALL.md](https://github.com/CVC4/CVC4/blob/master/INSTALL.md) for
  37   up-to-date instructions on how to build CVC4.
  38
  39 Changes since 1.5
  40 =================
  41
  42 New Features:
  43 * A new theory of floating points.
  44 * Novel approach for solving quantified bit-vectors (BV).
  45 * Eager bit-blasting: Support for SAT solver CaDiCaL.
  46 * A new Gaussian Elimination preprocessing pass for the theory of bit-vectors.
  47 * Support for transcendental functions (sin, cos, exp). In SMT2 input, this
  48   can be enabled by adding T to the logic (e.g., QF_NRAT).
  49 * Support for new operators in strings, including string inequality (str.<=)
  50   and string code (str.code).
  51 * Support for automated rewrite rule generation from sygus (*.sy) inputs using
  52   syntax-guided enumeration (option --sygus-rr).
  53
  54 Improvements:
  55 * Incremental unsat core support.
  56 * Further development of rewrite rules for the theory of strings and regular
  57   expressions.
  58 * Many optimizations for syntax-guided synthesis, including improved symmetry
  59   breaking for enumerative search and specialized algorithms for
  60   programming-by-examples conjectures.
  61
  62 Changes:
  63 * Eager bit-blasting: Removed support for SAT solver CryptoMinisat 4, added
  64   support for CryptoMinisat 5.
  65 * The LFSC proof checker now resides in its own repository on GitHub at
  66   https://github.com/CVC4/LFSC. It is not distributed with CVC4 anymore.
  67
  68 Changes since 1.4
  69 =================
  70
  71 * Improved heuristics for reasoning about non-linear arithmetic.
  72 * Native support for syntax-guided synthesis (sygus).
  73 * Support for many new heuristics for reasoning with quantifiers, including
  74   finite model finding.
  75 * Support for proofs for uninterpreted functions, arrays, bitvectors, and
  76   their combinations.
  77 * Performance improvements to existing theories.
  78 * A new theory of sets with cardinality and relations.
  79 * A new theory of strings.
  80 * Support for unsat cores.
  81 * Support for separation logic constraints.
  82 * Simplification mode "incremental" no longer supported.
  83 * Support for array constants in constraints.
  84 * Syntax for array models has changed in some language front-ends.
  85 * New input/output languages supported: "smt2.0" and "smtlib2.0" to
  86   force SMT-LIB v2.0; "smt2.5" and "smtlib2.5" to force SMT-LIB v2.5;
  87   "smt2.6" and "smtlib2.6" to force SMT-LIB v2.6;
  88   "smt", "smtlib", "smt2", and "smtlib2" all refer to the current standard
  89   version 2.6.  If an :smt-lib-version is set in the input, that overrides
  90   the command line.
  91 * Abstract values in SMT-LIB models are now ascribed types (with "as").
  92 * In SMT-LIB model output, real-sorted but integer-valued constants are
  93   now printed in accordance with the standard (e.g. "1.0").
  94
  95 Changes since 1.3
  96 =================
  97
  98 * CVC4 now supports libc++ in addition to libstdc++ (this especially
  99   helps on Mac OS Mavericks).
 100 * The LFSC proof checker has been incorporated into CVC4 sources.
 101 * Theory of finite sets, handling the MLSS fragment (singleton, union,
 102   intersection, set subtraction, membership and subset).
 103 * By default, CVC4 builds in "production" mode (optimized, with fewer
 104   internal checks on).  The common alternative is a "debug" build, which
 105   is much slower.  By default, CVC4 builds with no GPL'ed dependences.
 106   However, this is not the best-performing version; for that, you should
 107   configure with "--enable-gpl --best", which links against GPL'ed
 108   libraries that improve usability and performance.  For details on
 109   licensing and dependences, see the README file.
 110 * Small API adjustments to Datatypes to even out the API and make it
 111   function better in Java.
 112 * Timed statistics are now properly updated even on process abort.
 113 * Better automatic handling of output language setting when using CVC4
 114   via API.  Previously, the "automatic" language setting was sometimes
 115   (though not always) defaulting to the internal "AST" language; it
 116   should now (correctly) default to the same as the input language
 117   (if the input language is supported as an output language), or the
 118   "CVC4" native output language if no input language setting is applied.
 119 * The SmtEngine cannot be safely copied with the copy constructor.
 120   Previous versions inadvertently permitted clients to do this via the
 121   API.  This has been corrected, copy and assignment of the SmtEngine
 122   is no longer permitted.
 123
 124 Changes since 1.2
 125 =================
 126
 127 New features:
 128 * SMT-LIB-compliant support for abs, to_real, to_int, is_int, which were
 129   previously missing
 130 * New bv2nat/int2bv operators for bitvector/integer inter-compatibility.
 131 * Support in linear logics for /, div, and mod by constants (with the
 132   --rewrite-divk command line option).
 133 * Parsing support for TPTP's TFF and TFA formats.
 134 * A new theory of strings: word (dis-)equations, length constraints,
 135   regular expressions.
 136 * Increased compliance to SMT-LIBv2, numerous bugs and usability issues
 137   resolved.
 138 * New :command-verbosity SMT option to silence success and error messages
 139   on a per-command basis, and API changes to Command infrastructure to
 140   support this.
 141
 142 Behavioral changes:
 143 * It is no longer permitted to request model or proof generation if there's
 144   been an intervening push/pop.
 145 * User-defined symbols (define-funs) are no longer reported in the output
 146   of get-model commands.
 147 * Exit codes are now more standard for UNIX command-line tools.  Exit code
 148   zero means no error---but the result could be sat, unsat, or unknown---and
 149   nonzero means error.
 150
 151 API changes:
 152 * Expr::substitute() now capable of substituting operators (e.g.,
 153   function symbols under an APPLY_UF)
 154 * Numerous improvements to the Java language bindings
 155
 156 Changes since 1.1
 157 =================
 158
 159 * Real arithmetic now has three simplex solvers for exact precision linear
 160   arithmetic: the classical dual solver and two new solvers based on
 161   techniques for minimizing the sum of infeasibilities. GLPK can now be used
 162   as a heuristic backup to the exact precision solvers.  GLPK must be enabled
 163   at configure time. See --help for more information on enabling these solvers.
 164 * added support for "bit0" and "bit1" bitvector constants in SMT-LIB v1.2
 165 * support for theory "alternates": new ability to prototype new decision
 166   procedures that are selectable at runtime
 167 * various bugfixes
 168
 169 Changes since 1.0
 170 =================
 171
 172 * bit-vector solver now has a specialized decision procedure for unsigned bit-
 173   vector inequalities
 174 * numerous important bug fixes, performance improvements, and usability
 175   improvements
 176 * support for multiline input in interactive mode
 177 * Win32-building support via mingw
 178 * SMT-LIB get-model output now is easier to machine-parse: contains (model...)
 179 * user patterns for quantifier instantiation are now supported in the
 180   SMT-LIBv1.2 parser
 181 * --finite-model-find was incomplete when using --incremental, now fixed
 182 * the E-matching procedure is slightly improved
 183 * Boolean terms are now supported in datatypes
 184 * tuple and record support have been added to the compatibility library
 185 * driver verbosity change: for printing all commands as they're executed, you
 186   now need verbosity level >= 3 (e.g., -vvv) instead of level 1 (-v).  This
 187   allows tracing the solver's activities (with -v and -vv) without having too
 188   much output.
 189 * to make CVC4 quieter in abnormal (e.g., "warning" conditions), you can
 190   use -q.  Previously, this would silence all output (including "sat" or
 191   "unsat") as well.  Now, single -q silences messages and warnings, and
 192   double -qq silences all output (except on exception or signal).
 193