Revamp the multop interface to allow some basic optimizations like

not constructing a single-child multop.
* src/ltlast/multop.hh (multop::instance(type)): Remove.
(multop::instance(type, formula*, formula*)): Return a formula*.
(multop::instance(type, vec*)): Make it public and return a formula*.
(multop::add_sorted, multop::add):
* src/ltlast/multop.cc (multop::instance(type, vec*)): Rewrite.
(multop::instance(type)): Delete.
(multop::instance(type, formula*, formula*)): Adjust.
(multop::add_sorted, multop::add): Remove.
* src/ltlvisit/clone.cc (clone_visitor::visit(multop*)) Adjust.
* src/ltlvisit/nenoform.cc
(negative_normal_form_visitor::::visit(multop*)) Adjust.
* src/ltltest/equals.test: Make sure `a & a' and `a' are equals.
* wrap/python/tests/ltlsimple.py: Adjust.

ChangeLog

@@ -1,5 +1,21 @@
 2003-08-10  Alexandre Duret-Lutz  <aduret@src.lip6.fr>
 
+	Revamp the multop interface to allow some basic optimizations like
+	not constructing a single-child multop.
+	* src/ltlast/multop.hh (multop::instance(type)): Remove.
+	(multop::instance(type, formula*, formula*)): Return a formula*.
+	(multop::instance(type, vec*)): Make it public and return a formula*.
+	(multop::add_sorted, multop::add):
+	* src/ltlast/multop.cc (multop::instance(type, vec*)): Rewrite.
+	(multop::instance(type)): Delete.
+	(multop::instance(type, formula*, formula*)): Adjust.
+	(multop::add_sorted, multop::add): Remove.
+	* src/ltlvisit/clone.cc (clone_visitor::visit(multop*)) Adjust.
+	* src/ltlvisit/nenoform.cc
+	(negative_normal_form_visitor::::visit(multop*)) Adjust.
+	* src/ltltest/equals.test: Make sure `a & a' and `a' are equals.
+	* wrap/python/tests/ltlsimple.py: Adjust.
+
 	* src/tgba/succiterconcrete.cc, src/tgba/tgbaexplicit.cc,
 	src/tgba/tgbatba.cc, src/tgbaalgos/lbtt.cc: Use `-' instead of `& !'
 	between two BDDs.  That's one less call to BuDDy.

src/ltlast/multop.cc

@@ -1,6 +1,8 @@
 #include <cassert>
 #include <utility>
+#include <algorithm>
 #include "multop.hh"
+#include "constant.hh"
 #include "visitor.hh"
 #include "ltlvisit/destroy.hh"
 
@@ -77,10 +79,78 @@ namespace spot
 
     multop::map multop::instances;
 
-    multop*
+    formula*
     multop::instance(type op, vec* v)
     {
       pair p(op, v);
+
+      // Inline children of same kind.
+      {
+	vec inlined;
+	vec::iterator i = v->begin();
+	while (i != v->end())
+	  {
+	    multop* p = dynamic_cast<multop*>(*i);
+	    if (p && p->op() == op)
+	      {
+		unsigned ps = p->size();
+		for (unsigned n = 0; n < ps; ++n)
+		  inlined.push_back(p->nth(n));
+		// That sub-formula is now useless, drop it.
+		// Note that we use unref(), not destroy(), because we've
+		// adopted its children and don't want to destroy these.
+		formula::unref(*i);
+		i = v->erase(i);
+	      }
+	    else
+	      {
+		++i;
+	      }
+	  }
+	v->insert(v->end(), inlined.begin(), inlined.end());
+      }
+
+      std::sort(v->begin(), v->end());
+
+      // Remove duplicates.  We can't use std::unique(), because we
+      // must destroy() any formula we drop.
+      {
+	formula* last = 0;
+	vec::iterator i = v->begin();
+	while (i != v->end())
+	  {
+	    if (*i == last)
+	      {
+		destroy(*i);
+		i = v->erase(i);
+	      }
+	    else
+	      {
+		last = *i++;
+	      }
+	  }
+	}
+
+      if (v->size() == 0)
+	{
+	  delete v;
+	  switch (op)
+	    {
+	    case And:
+	      return constant::true_instance();
+	    case Or:
+	      return constant::false_instance();
+	    }
+	  /* Unreachable code.  */
+	  assert(0);
+	}
+      if (v->size() == 1)
+	{
+	  formula* res = (*v)[0];
+	  delete v;
+	  return res;
+	}
+
       map::iterator i = instances.find(p);
       if (i != instances.end())
 	{
@@ -93,75 +163,15 @@ namespace spot
 
     }
 
-    multop*
-    multop::instance(type op)
-    {
-      return instance(op, new vec);
-    }
-
-    multop*
+    formula*
     multop::instance(type op, formula* first, formula* second)
     {
       vec* v = new vec;
-      multop::add(op, v, first);
-      multop::add(op, v, second);
+      v->push_back(first);
+      v->push_back(second);
       return instance(op, v);
     }
 
-    void
-    multop::add_sorted(vec* v, formula* f)
-    {
-      // Keep V sorted.  When adding a new multop, iterate over all
-      // element until we find either an identical element, or the
-      // place where the new one should be inserted.
-      vec::iterator i;
-      for (i = v->begin(); i != v->end(); ++i)
-	{
-	  if (*i > f)
-	    break;
-	  if (*i == f)
-	    {
-	      // F is already a child.  Drop it.
-	      destroy(f);
-	      return;
-	    }
-	}
-      v->insert(i, f);
-    }
-
-    multop::vec*
-    multop::add(type op, vec* v, formula* f)
-    {
-      // If the formula we add is itself a multop for the same operator,
-      // merge its children.
-      multop* p = dynamic_cast<multop*>(f);
-      if (p && p->op() == op)
-	{
-	  unsigned ps = p->size();
-	  for (unsigned i = 0; i < ps; ++i)
-	    add_sorted(v, p->nth(i));
-	  // That sub-formula is now useless, drop it.
-	  // Note that we use unref(), not destroy(), because we've
-	  // adopted its children and don't want to destroy these.
-	  formula::unref(f);
-	}
-      else
-	{
-	  add_sorted(v, f);
-	}
-      return v;
-    }
-
-    void
-    multop::add(multop** m, formula* f)
-    {
-      vec* v = new vec(*(*m)->children_);
-      type op = (*m)->op();
-      multop::add(op, v, f);
-      formula::unref(*m);
-      *m = instance(op, v);
-    }
-
     unsigned
     multop::instance_count()
     {

src/ltlast/multop.hh

@@ -18,29 +18,36 @@ namespace spot
     public:
       enum type { Or, And };
 
-
-      /// \brief Build a spot::ltl::multop with no child.
-      ///
-      /// This has little value unless you call multop::add later.
-      static multop* instance(type op);
+      /// List of formulae.
+      typedef std::vector<formula*> vec;
 
       /// \brief Build a spot::ltl::multop with two children.
       ///
       /// If one of the children itself is a spot::ltl::multop
       /// with the same type, it will be merged.  I.e., children
       /// if that child will be added, and that child itself will
-      /// be destroyed.
-      static multop* instance(type op, formula* first, formula* second);
+      /// be destroyed.  This allows incremental building of
+      /// n-ary ltl::multop.
+      ///
+      /// This functions can perform slight optimizations and
+      /// may not return an ltl::multop objects.  For instance
+      /// if \c first and \c second are equal, that formula is
+      /// returned as-is.
+      static formula* instance(type op, formula* first, formula* second);
 
-      /// \brief Add another child to this operator.
+      /// \brief Build a spot::ltl::multop with many children.
       ///
-      /// If \a f itself is a spot::ltl::multop with the same type, it
-      /// will be merged.  I.e., children of \a f will be added, and
-      /// that \a f will will be destroyed.
+      /// Same as the other instance() function, but take a vector of
+      /// formula in argument.  This vector is acquired by the
+      /// spot::ltl::multop class, the caller should allocate it with
+      /// \c new, but not use it (especially not destroy it) after it
+      /// has been passed to spot::ltl::multop.
       ///
-      /// Note that this function overwrites the supplied ltl::multop pointer.
-      /// The old value is released and should not be used after this.
-      static void add(multop** m, formula* f);
+      /// This functions can perform slight optimizations and
+      /// may not return an ltl::multop objects.  For instance
+      /// if the vector contain only one unique element, this
+      /// this formula will be returned as-is.
+      static formula* instance(type op, vec* v);
 
       virtual void accept(visitor& v);
       virtual void accept(const_visitor& v) const;
@@ -65,10 +72,6 @@ namespace spot
       static unsigned instance_count();
 
     protected:
-      // Sorted list of formulae.  (Sorted by pointer comparison.)
-      typedef std::vector<formula*> vec;
-
-
       typedef std::pair<type, vec*> pair;
       /// Comparison functor used internally by ltl::multop.
       struct paircmp
@@ -85,10 +88,6 @@ namespace spot
       static map instances;
 
       multop(type op, vec* v);
-      static multop* instance(type op, vec* v);
-      static vec* add(type op, vec* v, formula* f);
-      static void add_sorted(vec* v, formula* f);
-
       virtual ~multop();
 
     private:

src/ltltest/equals.test

@@ -25,6 +25,7 @@ check 0 'a && b & a' 'b & a & b'
 check 0 'a & b' 'b & a & b'
 check 0 'a & b' 'b & a & a'
 check 0 'a & b & (c |(f U g)|| e)' 'b & a & a & (c | e |(f U g)| e | c) & b'
+check 0 'a & a' 'a'
 
 # other formulae which are not
 check 1 'a' 'b'

src/ltlvisit/clone.cc

@@ -47,13 +47,11 @@ namespace spot
     void
     clone_visitor::visit(multop* mo)
     {
-      multop* res = multop::instance(mo->op());
+      multop::vec* res = new multop::vec;
       unsigned mos = mo->size();
       for (unsigned i = 0; i < mos; ++i)
-	{
-	  multop::add(&res, recurse(mo->nth(i)));
-	}
-      result_ = res;
+	res->push_back(recurse(mo->nth(i)));
+      result_ = multop::instance(mo->op(), res);
     }
 
     formula*

src/ltlvisit/nenoform.cc

@@ -143,11 +143,11 @@ namespace spot
 	      op = multop::And;
 	      break;
 	    }
-	multop* res = multop::instance(op);
+	multop::vec* res = new multop::vec;
 	unsigned mos = mo->size();
 	for (unsigned i = 0; i < mos; ++i)
-	  multop::add(&res, recurse(mo->nth(i)));
-	result_ = res;
+	  res->push_back(recurse(mo->nth(i)));
+	result_ = multop::instance(op, res);
       }
 
       formula*

src/tgba/succiterconcrete.cc

@@ -67,8 +67,9 @@ namespace spot
       {
 	// FIXME: Iterating on the successors this way (calling
 	// bdd_satone{,set} and NANDing out (-=) the result from a
-	// set) requires several descent of the BDD.  Maybe it would be
-	// faster to compute all satisfying formula in one operation.
+	// set) requires several descents of the BDD.  Maybe it would
+	// be faster to compute all satisfying formulae in one
+	// operation.
 
 	succ_set_left_ -= current_;
 	if (succ_set_left_ == bddfalse) // No more successors?

wrap/python/tests/ltlsimple.py

@@ -33,12 +33,12 @@ assert op2 == op3
 op4 = spot.multop.instance(spot.multop.Or, op2, op3)
 
 print 'op4 =', op4
-assert op4.nth(0) == op2
+assert op4 == op2
 
 del op2, op3
 
 assert spot.atomic_prop.instance_count() == 3
-assert spot.multop.instance_count() == 2
+assert spot.multop.instance_count() == 1
 
 spot.destroy(op4)
 del op4