split out restart

src/math/polysat/restart.cpp

@@ -0,0 +1,44 @@
+/*++
+Copyright (c) 2021 Microsoft Corporation
+
+Module Name:
+
+    Restart
+
+Author:
+
+    Jakob Rath, Nikolaj Bjorner (nbjorner) 2021-12-12
+
+  
+--*/
+#include "math/polysat/solver.h"
+#include "math/polysat/restart.h"
+#include "util/luby.h"
+
+namespace polysat {
+
+    restart::restart(solver& s):
+        s(s)
+    {}
+
+    /*
+    * Basic restart functionality.
+    * restarts make more sense when the order of variable 
+    * assignments and the values assigned to variables can be diversified.
+    */
+    bool restart::should_apply() const {
+        if (s.m_stats.m_num_conflicts - m_conflicts_at_restart < m_restart_threshold)
+            return false;
+        if (s.base_level() + 2 > s.m_level)
+            return false;
+        return true;        
+    }
+
+    void restart::operator()() {
+        ++s.m_stats.m_num_restarts;
+        s.pop_levels(s.m_level - s.base_level());
+        m_conflicts_at_restart = s.m_stats.m_num_conflicts;
+        m_restart_threshold = m_restart_init * get_luby(++m_luby_idx);
+    }
+
+}