adding outline for parallel tactic

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

src/tactic/portfolio/parallel_tactic.cpp

@@ -0,0 +1,48 @@
+/*++
+Copyright (c) 2017 Microsoft Corporation
+
+Module Name:
+
+    parallel_solver.cpp
+
+Abstract:
+
+    Parallel solver in the style of Treengeling.
+
+    It assumes a solver that supports good lookaheads.
+    
+
+Author:
+
+    Nikolaj Bjorner (nbjorner) 2017-10-9
+
+Notes:
+   
+--*/
+
+#include "solver/solver.h"
+#include "tactic/tactic.h"
+
+class parallel_tactic : public tactic {
+    ref<solver> m_solver;
+public:
+    parallel_tactic(solver* s) : m_solver(s) {}
+
+    void operator ()(const goal_ref & g,goal_ref_buffer & result,model_converter_ref & mc,proof_converter_ref & pc,expr_dependency_ref & dep) {
+        NOT_IMPLEMENTED_YET();
+    }
+
+    void cleanup() {
+        NOT_IMPLEMENTED_YET();
+    }
+
+    tactic* translate(ast_manager& m) {
+        NOT_IMPLEMENTED_YET();
+        return 0;
+    }
+};
+
+tactic * mk_parallel_tactic(solver* s) {
+    return alloc(parallel_tactic, s);
+}
+