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