/*++
Copyright (c) 2011 Microsoft Corporation

Module Name:

    var_queue.h

Abstract:

    SAT variable priority queue.

Author:

    Leonardo de Moura (leonardo) 2011-05-21.

Revision History:

--*/
#pragma once

#include "util/heap.h"


    
class var_queue {
    typedef unsigned var;

    struct lt {
        svector<unsigned> & m_activity;
    lt(svector<unsigned> & act):m_activity(act) {}
        bool operator()(var v1, var v2) const { return m_activity[v1] > m_activity[v2]; }
    };
    heap<lt>  m_queue;
public:

    
    var_queue(svector<unsigned> & act):m_queue(128, lt(act)) {}
    
    void activity_increased_eh(var v) {
        if (m_queue.contains(v))
            m_queue.decreased(v);
    }
    
    void activity_changed_eh(var v, bool up) {
        if (m_queue.contains(v)) {
            if (up) 
                m_queue.decreased(v);
            else 
                m_queue.increased(v);
        }
    }
    
    void mk_var_eh(var v) {
        m_queue.reserve(v+1);
        m_queue.insert(v);
    }
    
    void del_var_eh(var v) {
        if (m_queue.contains(v))
            m_queue.erase(v);
    }
    
    void unassign_var_eh(var v) {
        if (!m_queue.contains(v))
            m_queue.insert(v);
    }
    
    void reset() {
        m_queue.reset();
    }
    
    bool empty() const { return m_queue.empty(); }
    
    var next_var() { SASSERT(!empty()); return m_queue.erase_min(); }
    
    var min_var() { SASSERT(!empty()); return m_queue.min_value(); }
    
    bool more_active(var v1, var v2) const { return m_queue.less_than(v1, v2); }
};