fix transitive reduction bug, eliminate blocked tag on binary clauses, separate BIG structure from scc

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

src/sat/sat_big.h

@@ -0,0 +1,55 @@
+/*++
+Copyright (c) 2017 Microsoft Corporation
+
+Module Name:
+
+    sat_big.h
+
+Abstract:
+
+    binary implication graph structure.
+
+Author:
+
+    Nikolaj Bjorner (nbjorner) 2017-12-13.
+
+Revision History:
+
+--*/
+#ifndef SAT_BIG_H_
+#define SAT_BIG_H_
+
+#include "sat/sat_types.h"
+#include "util/statistics.h"
+#include "util/params.h"
+
+namespace sat {
+    class solver;
+
+    class big {
+        random_gen             m_rand;
+        unsigned               m_num_vars;
+        vector<literal_vector> m_dag;
+        svector<bool>          m_roots;
+        svector<int>           m_left, m_right;
+        literal_vector         m_root, m_parent;
+
+        void init_dfs_num(bool learned);
+        struct pframe;
+
+    public:
+
+        big();
+        void init_big(solver& s, bool learned);
+        void ensure_big(solver& s, bool learned) { if (m_left.empty()) init_big(s, learned); }
+        int get_left(literal l) const { return m_left[l.index()]; }
+        int get_right(literal l) const { return m_right[l.index()]; }
+        literal get_parent(literal l) const { return m_parent[l.index()]; }
+        literal get_root(literal l) const { return m_root[l.index()]; }
+        bool reaches(literal u, literal v) const { return m_left[u.index()] < m_left[v.index()] && m_right[v.index()] < m_right[u.index()]; }        
+        bool connected(literal u, literal v) const { return reaches(u, v) || reaches(~v, ~u); }
+        void display(std::ostream& out) const;
+    };
+};
+
+#endif