merge

2 files changed, 149 insertions, 0 deletions

diff --git a/src/sat/bsat/satSolver.c b/src/sat/bsat/satSolver.c
index df9ada8e..fe7e65fe 100644
--- a/src/sat/bsat/satSolver.c
+++ b/src/sat/bsat/satSolver.c
@@ -2168,6 +2168,153 @@ int sat_solver_solve_lexsat( sat_solver* s, int * pLits, int nLits )
     return status;
 }
 
+// This procedure is called on a set of assumptions to minimize their number.
+// The procedure relies on the fact that the current set of assumptions is UNSAT.  
+// It receives and returns SAT solver without assumptions. It returns the number 
+// of assumptions after minimization. The set of assumptions is returned in pLits.
+int sat_solver_minimize_assumptions( sat_solver* s, int * pLits, int nLits, int nConfLimit )
+{
+    int i, k, nLitsL, nLitsR, nResL, nResR;
+    if ( nLits == 1 )
+    {
+        // since the problem is UNSAT, we will try to solve it without assuming the last literal
+        // if the result is UNSAT, the last literal can be dropped; otherwise, it is needed
+        int status = l_False;
+        int Temp = s->nConfLimit; 
+        s->nConfLimit = nConfLimit;
+        status = sat_solver_solve_internal( s );
+        s->nConfLimit = Temp;
+        return (int)(status != l_False); // return 1 if the problem is not UNSAT
+    }
+    assert( nLits >= 2 );
+    nLitsL = nLits / 2;
+    nLitsR = nLits - nLitsL;
+    // assume the left lits
+    for ( i = 0; i < nLitsL; i++ )
+        if ( !sat_solver_push(s, pLits[i]) )
+        {
+            for ( k = i; k >= 0; k-- )
+                sat_solver_pop(s);
+            return sat_solver_minimize_assumptions( s, pLits, i+1, nConfLimit );
+        }
+    // solve for the right lits
+    nResL = sat_solver_minimize_assumptions( s, pLits + nLitsL, nLitsR, nConfLimit );
+    for ( i = 0; i < nLitsL; i++ )
+        sat_solver_pop(s);
+    // swap literals
+//    assert( nResL <= nLitsL );
+//    for ( i = 0; i < nResL; i++ )
+//        ABC_SWAP( int, pLits[i], pLits[nLitsL+i] );
+    veci_resize( &s->temp_clause, 0 );
+    for ( i = 0; i < nLitsL; i++ )
+        veci_push( &s->temp_clause, pLits[i] );
+    for ( i = 0; i < nResL; i++ )
+        pLits[i] = pLits[nLitsL+i];
+    for ( i = 0; i < nLitsL; i++ )
+        pLits[nResL+i] = veci_begin(&s->temp_clause)[i];
+    // assume the right lits
+    for ( i = 0; i < nResL; i++ )
+        if ( !sat_solver_push(s, pLits[i]) )
+        {
+            for ( k = i; k >= 0; k-- )
+                sat_solver_pop(s);
+            return sat_solver_minimize_assumptions( s, pLits, i+1, nConfLimit );
+        }
+    // solve for the left lits
+    nResR = sat_solver_minimize_assumptions( s, pLits + nResL, nLitsL, nConfLimit );
+    for ( i = 0; i < nResL; i++ )
+        sat_solver_pop(s);
+    return nResL + nResR;
+}
+
+// This is a specialized version of the above procedure with several custom changes:
+// - makes sure that at least one of the marked literals is preserved in the clause
+// - sets literals to zero when they do not have to be used
+// - sets literals to zero for disproved variables
+int sat_solver_minimize_assumptions2( sat_solver* s, int * pLits, int nLits, int nConfLimit )
+{
+    int i, k, nLitsL, nLitsR, nResL, nResR;
+    if ( nLits == 1 )
+    {
+        // since the problem is UNSAT, we will try to solve it without assuming the last literal
+        // if the result is UNSAT, the last literal can be dropped; otherwise, it is needed
+        int RetValue = 1, LitNot = Abc_LitNot(pLits[0]);
+        int status = l_False;
+        int Temp = s->nConfLimit; 
+        s->nConfLimit = nConfLimit;
+
+        RetValue = sat_solver_push( s, LitNot ); assert( RetValue );
+        status = sat_solver_solve_internal( s );
+        sat_solver_pop( s );
+
+        // if the problem is UNSAT, add clause
+        if ( status == l_False )
+        {
+            RetValue = sat_solver_addclause( s, &LitNot, &LitNot+1 );
+            assert( RetValue );
+        }
+
+        s->nConfLimit = Temp;
+        return (int)(status != l_False); // return 1 if the problem is not UNSAT
+    }
+    assert( nLits >= 2 );
+    nLitsL = nLits / 2;
+    nLitsR = nLits - nLitsL;
+    // assume the left lits
+    for ( i = 0; i < nLitsL; i++ )
+        if ( !sat_solver_push(s, pLits[i]) )
+        {
+            for ( k = i; k >= 0; k-- )
+                sat_solver_pop(s);
+
+            // add clauses for these literal
+            for ( k = i+1; k > nLitsL; k++ )
+            {
+                int LitNot = Abc_LitNot(pLits[i]);
+                int RetValue = sat_solver_addclause( s, &LitNot, &LitNot+1 );
+                assert( RetValue );
+            }
+
+            return sat_solver_minimize_assumptions2( s, pLits, i+1, nConfLimit );
+        }
+    // solve for the right lits
+    nResL = sat_solver_minimize_assumptions2( s, pLits + nLitsL, nLitsR, nConfLimit );
+    for ( i = 0; i < nLitsL; i++ )
+        sat_solver_pop(s);
+    // swap literals
+//    assert( nResL <= nLitsL );
+    veci_resize( &s->temp_clause, 0 );
+    for ( i = 0; i < nLitsL; i++ )
+        veci_push( &s->temp_clause, pLits[i] );
+    for ( i = 0; i < nResL; i++ )
+        pLits[i] = pLits[nLitsL+i];
+    for ( i = 0; i < nLitsL; i++ )
+        pLits[nResL+i] = veci_begin(&s->temp_clause)[i];
+    // assume the right lits
+    for ( i = 0; i < nResL; i++ )
+        if ( !sat_solver_push(s, pLits[i]) )
+        {
+            for ( k = i; k >= 0; k-- )
+                sat_solver_pop(s);
+
+            // add clauses for these literal
+            for ( k = i+1; k > nResL; k++ )
+            {
+                int LitNot = Abc_LitNot(pLits[i]);
+                int RetValue = sat_solver_addclause( s, &LitNot, &LitNot+1 );
+                assert( RetValue );
+            }
+
+            return sat_solver_minimize_assumptions2( s, pLits, i+1, nConfLimit );
+        }
+    // solve for the left lits
+    nResR = sat_solver_minimize_assumptions2( s, pLits + nResL, nLitsL, nConfLimit );
+    for ( i = 0; i < nResL; i++ )
+        sat_solver_pop(s);
+    return nResL + nResR;
+}
+
+
 
 int sat_solver_nvars(sat_solver* s)
 {
diff --git a/src/sat/bsat/satSolver.h b/src/sat/bsat/satSolver.h
index 5a8483c1..5191b2cd 100644
--- a/src/sat/bsat/satSolver.h
+++ b/src/sat/bsat/satSolver.h
@@ -50,6 +50,8 @@ extern int         sat_solver_simplify(sat_solver* s);
 extern int         sat_solver_solve(sat_solver* s, lit* begin, lit* end, ABC_INT64_T nConfLimit, ABC_INT64_T nInsLimit, ABC_INT64_T nConfLimitGlobal, ABC_INT64_T nInsLimitGlobal);
 extern int         sat_solver_solve_internal(sat_solver* s);
 extern int         sat_solver_solve_lexsat(sat_solver* s, int * pLits, int nLits);
+extern int         sat_solver_minimize_assumptions( sat_solver* s, int * pLits, int nLits, int nConfLimit );
+extern int         sat_solver_minimize_assumptions2( sat_solver* s, int * pLits, int nLits, int nConfLimit );
 extern int         sat_solver_push(sat_solver* s, int p);
 extern void        sat_solver_pop(sat_solver* s);
 extern void        sat_solver_set_resource_limits(sat_solver* s, ABC_INT64_T nConfLimit, ABC_INT64_T nInsLimit, ABC_INT64_T nConfLimitGlobal, ABC_INT64_T nInsLimitGlobal);