Add RestartStop

This commit adds the RestartStop class that checks whether a given
cutoff for the number of restarts is reached. The RestartStop also made
part of CombinedStop.

changelog.in

@@ -69,6 +69,16 @@ Date: 2020-??-??
 [DESCRIPTION]
 Let's see.
 
+[ENTRY]
+Module: search 
+What:   new
+Rank:   minor
+Thanks: Jip J. Dekker
+[DESCRIPTION]
+Add RestartStop class to enforce a limit on the amount of restarts conducted
+in a search. RestartStop is included in CombinedStop and accessible from the
+FlatZinc interface through the --restart-limit flag.
+
 [RELEASE]
 Version: 6.3.0
 Date: 2020-??-??

gecode/driver.hh

@@ -440,6 +440,8 @@ namespace Gecode {
     Driver::StringOption      _restart;       ///< Restart method option
     Driver::DoubleOption      _r_base;        ///< Restart base
     Driver::UnsignedIntOption _r_scale;       ///< Restart scale factor
+    Driver::UnsignedLongLongIntOption
+                              _r_limit;       ///< Cutoff for number of restarts 
     Driver::BoolOption        _nogoods;       ///< Whether to use no-goods
     Driver::UnsignedIntOption _nogoods_limit; ///< Limit for no-good extraction
     Driver::DoubleOption      _relax;         ///< Probability to relax variable
@@ -591,6 +593,11 @@ namespace Gecode {
     /// Return restart scale factor
     unsigned int restart_scale(void) const;
 
+    /// Set default restart cutoff
+    void restart_limit(unsigned long long int n);
+    /// Return restart cutoff
+    unsigned long long int restart_limit(void) const;
+
     /// Set default nogoods posting behavior
     void nogoods(bool b);
     /// Return whether nogoods are used

gecode/driver/options.cpp

@@ -637,6 +637,7 @@ namespace Gecode {
               Search::Config::base),
       _r_scale("restart-scale","scale factor for restart sequence",
                Search::Config::slice),
+      _r_limit("restart-limit","restart cutoff (0 = none, solution mode)"),
       _nogoods("nogoods","whether to use no-goods from restarts",false),
       _nogoods_limit("nogoods-limit","depth limit for no-good extraction",
                      Search::Config::nogoods_limit),
@@ -679,7 +680,7 @@ namespace Gecode {
     add(_d_l);
     add(_node); add(_fail); add(_time); add(_interrupt);
     add(_assets); add(_slice);
-    add(_restart); add(_r_base); add(_r_scale);
+    add(_restart); add(_r_base); add(_r_scale); add(_r_limit);
     add(_nogoods); add(_nogoods_limit);
     add(_relax);
     add(_mode); add(_iterations); add(_samples); add(_print_last);

gecode/driver/options.hpp

@@ -425,6 +425,15 @@ namespace Gecode {
     return _r_scale.value();
   }
 
+  inline void
+  Options::restart_limit(unsigned long long int n) {
+    _r_limit.value(n);
+  }
+  inline unsigned long long int
+  Options::restart_limit(void) const {
+    return _r_limit.value();
+  }
+
   inline void
   Options::nogoods(bool b) {
     _nogoods.value(b);

gecode/driver/script.hpp

@@ -52,15 +52,18 @@ namespace Gecode { namespace Driver {
     Search::NodeStop* ns; ///< Used node stop object
     Search::FailStop* fs; ///< Used fail stop object
     Search::TimeStop* ts; ///< Used time stop object
+    Search::RestartStop* rs; ///< Used restart stop object
     GECODE_DRIVER_EXPORT
     static bool sigint;   ///< Whether search was interrupted using Ctrl-C
     /// Initialize stop object
     CombinedStop(unsigned long long int node, 
                  unsigned long long int fail,
-                 double time)
+                 double time,
+                 unsigned long long int restart)
       : ns((node > 0ULL) ? new Search::NodeStop(node) : nullptr),
         fs((fail > 0ULL) ? new Search::FailStop(fail) : nullptr),
-        ts((time > 0.0)  ? new Search::TimeStop(time) : nullptr) {
+        ts((time > 0.0)  ? new Search::TimeStop(time) : nullptr),
+        rs((restart > 0.0) ? new Search::RestartStop(restart) : nullptr) {
       sigint = false;
     }
   public:
@@ -69,34 +72,38 @@ namespace Gecode { namespace Driver {
       SR_NODE = 1 << 0, ///< Node limit reached
       SR_FAIL = 1 << 1, ///< Fail limit reached
       SR_TIME = 1 << 2, ///< Time limit reached
-      SR_INT  = 1 << 3  ///< Interrupted by user
+      SR_RESTART = 1 << 3, ///< Time limit reached
+      SR_INT  = 1 << 4  ///< Interrupted by user
     };
     /// Test whether search must be stopped
     virtual bool stop(const Search::Statistics& s, const Search::Options& o) {
       return
         sigint ||
         ((ns != nullptr) && ns->stop(s,o)) ||
         ((fs != nullptr) && fs->stop(s,o)) ||
-        ((ts != nullptr) && ts->stop(s,o));
+        ((ts != nullptr) && ts->stop(s,o)) ||
+        ((rs != nullptr) && rs->stop(s,o));
     }
     /// Report reason why search has been stopped
     int reason(const Search::Statistics& s, const Search::Options& o) {
       return
         (((ns != nullptr) && ns->stop(s,o)) ? SR_NODE : 0) |
         (((fs != nullptr) && fs->stop(s,o)) ? SR_FAIL : 0) |
         (((ts != nullptr) && ts->stop(s,o)) ? SR_TIME : 0) |
+        (((rs != nullptr) && rs->stop(s,o)) ? SR_RESTART : 0) |
         (sigint                          ? SR_INT  : 0);
     }
     /// Create appropriate stop-object
     static Search::Stop*
     create(unsigned long long int node,
            unsigned long long int fail,
            double time,
+					 unsigned long long int restart,
            bool intr) {
-      if (!intr && (node == 0ULL) && (fail == 0ULL) && (time == 0.0))
+      if (!intr && (node == 0ULL) && (fail == 0ULL) && (time == 0.0) && (restart == 0ULL))
         return nullptr;
       else
-        return new CombinedStop(node,fail,time);
+        return new CombinedStop(node,fail,time,restart);
     }
 #ifdef GECODE_THREADS_WINDOWS
     /// Handler for catching Ctrl-C
@@ -128,7 +135,7 @@ namespace Gecode { namespace Driver {
     }
     /// Destructor
     ~CombinedStop(void) {
-      delete ns; delete fs; delete ts;
+      delete ns; delete fs; delete ts; delete rs;
     }
   };
 
@@ -379,7 +386,7 @@ namespace Gecode { namespace Driver {
           so.d_l     = o.d_l();
           so.assets  = o.assets();
           so.slice   = o.slice();
-          so.stop    = CombinedStop::create(o.node(),o.fail(), o.time(),
+          so.stop    = CombinedStop::create(o.node(),o.fail(), o.time(), o.restart_limit(),
                                             o.interrupt());
           so.cutoff  = createCutoff(o);
           so.clone   = false;
@@ -431,6 +438,8 @@ namespace Gecode { namespace Driver {
                   l_out << "fail ";
                 if (r & CombinedStop::SR_TIME)
                   l_out << "time ";
+                if (r & CombinedStop::SR_RESTART)
+                  l_out << "restart ";
                 l_out << "limit reached" << endl << endl;
               }
             }
@@ -480,7 +489,7 @@ namespace Gecode { namespace Driver {
           so.c_d     = o.c_d();
           so.a_d     = o.a_d();
           so.d_l     = o.d_l();
-          so.stop    = CombinedStop::create(o.node(),o.fail(), o.time(),
+          so.stop    = CombinedStop::create(o.node(),o.fail(), o.time(), o.restart_limit(),
                                             o.interrupt());
           so.cutoff  = createCutoff(o);
           so.nogoods_limit = o.nogoods() ? o.nogoods_limit() : 0U;
@@ -542,7 +551,7 @@ namespace Gecode { namespace Driver {
               sok.c_d     = o.c_d();
               sok.a_d     = o.a_d();
               sok.d_l     = o.d_l();
-              sok.stop    = CombinedStop::create(o.node(),o.fail(), o.time(),
+              sok.stop    = CombinedStop::create(o.node(),o.fail(), o.time(), o.restart_limit(),
                                                  false);
               sok.cutoff  = createCutoff(o);
               sok.nogoods_limit = o.nogoods() ? o.nogoods_limit() : 0U;

gecode/flatzinc.hh

@@ -242,6 +242,7 @@ namespace Gecode { namespace FlatZinc {
       Gecode::Driver::StringOption      _restart;   ///< Restart method option
       Gecode::Driver::DoubleOption      _r_base;    ///< Restart base
       Gecode::Driver::UnsignedIntOption _r_scale;   ///< Restart scale factor
+      Gecode::Driver::UnsignedLongLongIntOption _r_limit; ///< Cutoff for number of restarts 
       Gecode::Driver::BoolOption        _nogoods;   ///< Whether to use no-goods
       Gecode::Driver::UnsignedIntOption _nogoods_limit; ///< Depth limit for extracting no-goods
       Gecode::Driver::BoolOption        _interrupt; ///< Whether to catch SIGINT
@@ -279,6 +280,7 @@ namespace Gecode { namespace FlatZinc {
       _restart("restart","restart sequence type",RM_NONE),
       _r_base("restart-base","base for geometric restart sequence",1.5),
       _r_scale("restart-scale","scale factor for restart sequence",250),
+      _r_limit("restart-limit","restart cutoff (0 = none, solution mode)"),
       _nogoods("nogoods","whether to use no-goods from restarts",false),
       _nogoods_limit("nogoods-limit","depth limit for no-good extraction",
                      Search::Config::nogoods_limit),
@@ -310,7 +312,7 @@ namespace Gecode { namespace FlatZinc {
       add(_node); add(_fail); add(_time); add(_time_limit); add(_interrupt);
       add(_seed);
       add(_step);
-      add(_restart); add(_r_base); add(_r_scale);
+      add(_restart); add(_r_base); add(_r_scale); add(_r_limit);
       add(_nogoods); add(_nogoods_limit);
       add(_mode); add(_stat);
       add(_output);
@@ -366,6 +368,7 @@ namespace Gecode { namespace FlatZinc {
     void restart_base(double d) { _r_base.value(d); }
     unsigned int restart_scale(void) const { return _r_scale.value(); }
     void restart_scale(int i) { _r_scale.value(i); }
+    unsigned long long int restart_limit(void) const { return _r_limit.value(); }
     bool nogoods(void) const { return _nogoods.value(); }
     unsigned int nogoods_limit(void) const { return _nogoods_limit.value(); }
     bool interrupt(void) const { return _interrupt.value(); }

gecode/flatzinc/flatzinc.cpp

@@ -1836,7 +1836,7 @@ namespace Gecode { namespace FlatZinc {
       n_p = PropagatorGroup::all.size(*this);
     }
     Search::Options o;
-    o.stop = Driver::CombinedStop::create(opt.node(), opt.fail(), opt.time(),
+    o.stop = Driver::CombinedStop::create(opt.node(), opt.fail(), opt.time(), opt.restart_limit(),
                                           true);
     o.c_d = opt.c_d();
     o.a_d = opt.a_d();

gecode/search.hh

@@ -816,6 +816,8 @@ namespace Gecode { namespace Search {
     static Stop* fail(unsigned long long int l);
     /// Stop if time limit \a l (in milliseconds) has been exceeded
     static Stop* time(double l);
+    /// Stop if restart limit \a l has been exceeded
+    static Stop* restart(unsigned long long int l);
     //@}
   };
 
@@ -888,6 +890,25 @@ namespace Gecode { namespace Search {
     virtual bool stop(const Statistics& s, const Options& o);
   };
 
+  /**
+   * \brief %Stop-object based on number of restarts
+   * \ingroup TaskModelSearchStop
+   */
+  class GECODE_SEARCH_EXPORT RestartStop : public Stop {
+  protected:
+    /// Restart limit
+    unsigned long long int l;
+  public:
+    /// Stop if restart limit \a l is exceeded
+    RestartStop(unsigned long long int l);
+    /// Return current limit
+    unsigned long long int limit(void) const;
+    /// Set current limit to \a l restarts 
+    void limit(unsigned long long int l);
+    /// Return true if failure limit is exceeded
+    virtual bool stop(const Statistics& s, const Options& o);
+  };
+
 }}
 
 #include <gecode/search/stop.hpp>

gecode/search/stop.cpp

@@ -51,6 +51,10 @@ namespace Gecode { namespace Search {
   Stop::time(double l) {
     return new TimeStop(l);
   }
+  Stop*
+  Stop::restart(unsigned long long int  l) {
+    return new RestartStop(l);
+  }
 
 
   /*
@@ -82,6 +86,14 @@ namespace Gecode { namespace Search {
     return t.stop() > l;
   }
 
+  /*
+   * Stopping for restart limit
+   *
+   */
+  bool
+  RestartStop::stop(const Statistics& s, const Options&) {
+    return s.restart > l;
+  }
 
 }}
 

gecode/search/stop.hpp

@@ -107,6 +107,24 @@ namespace Gecode { namespace Search {
     t.start();
   }
 
+  /*
+   * Stopping for restart limit
+   *
+   */
+
+  forceinline
+  RestartStop::RestartStop(unsigned long long int l0) : l(l0) {}
+
+  forceinline unsigned long long int
+  RestartStop::limit(void) const {
+    return l;
+  }
+
+  forceinline void
+  RestartStop::limit(unsigned long long int l0) {
+    l=l0;
+  }
+
 }}
 
 // STATISTICS: search-other

tools/flatzinc/gecode.msc.in

@@ -21,6 +21,7 @@
     ],
     ["--restart-base", "Base for geometric restart sequence", "float", "1.5"],
     ["--restart-scale", "Scale factor for restart sequence", "int", "250"],
+    ["--restart-limit", "Restart cutoff", "int", "0"],
     ["--nogoods", "Use no-goods from restarts", "bool", "false"],
     ["--nogoods-limit", "Depth limit for no-good extraction", "int", "128"]
   ],