prepare for tuned viable sets

Signed-off-by: Nikolaj Bjorner <nbjorner@microsoft.com>

src/math/dd/dd_bdd.cpp

@@ -1193,5 +1193,4 @@ namespace dd {
         return r;
     }
 
-
 }

src/math/dd/dd_bdd.h

@@ -259,6 +259,7 @@ namespace dd {
         bool is_constv(bddv const& a);
         rational to_val(bddv const& a);
 
+
         std::ostream& display(std::ostream& out);
         std::ostream& display(std::ostream& out, bdd const& b);
 

src/math/dd/dd_fdd.cpp

@@ -120,4 +120,36 @@ namespace dd {
         return out;
     }
 
+  
+    bool fdd::sup(bdd const& x, bool_vector& lo) {
+        SASSERT(lo.size() == num_bits());
+	//
+	// Assumption: common case is that high-order bits are before lower-order bits also
+	// after re-ordering.
+	//
+
+	// this checks that lo is included in x
+	bdd b = x;
+	while (!b.is_true()) {
+	    unsigned const pos = var2pos(b.var());
+            SASSERT(pos != UINT_MAX && "Unexpected BDD variable");
+	    if (lo[pos] && b.hi().is_false())
+		return false;
+	    if (!lo[pos] && b.lo().is_false())
+		return false;
+	    
+	    if (lo[pos])
+		b = b.hi();
+	    else
+		b = b.lo();
+	}
+	return false;
+    }
+    
+    bool fdd::inf(bdd const& b, bool_vector& hi) {
+        SASSERT(hi.size() == num_bits());
+	return false;
+    }
+
+
 }

src/math/dd/dd_fdd.h

@@ -11,8 +11,8 @@ Abstract:
 
 Author:
 
-    Nikolaj Bjorner (nbjorner) 2021-04-20
     Jakob Rath 2021-04-20
+    Nikolaj Bjorner (nbjorner) 2021-04-20
 
 --*/
 #pragma once
@@ -71,6 +71,23 @@ namespace dd {
 
         /** Like find, but returns hint if it is contained in the BDD. */
         find_t find_hint(bdd b, rational const& hint, rational& out_val) const;
+
+
+
+	/*
+	 * find largest value at lo or above such that bdd b evaluates to true
+	 * at lo and all values between.
+	 * dually, find smallest value below hi that evaluates b to true
+	 * and all values between the value and hi also evaluate b to true.
+	 * \param b - a bdd using variables from this
+	 * \param lo/hi - bound to be traversed.
+	 * \return false if b is false at lo/hi
+	 * \pre variables in b are a subset of variables from the fdd
+	 */ 
+	bool sup(bdd const& b, bool_vector& lo);
+      
+	bool inf(bdd const& b, bool_vector& hi); 
+      
     };
 
 }