/*
    Copyright 2005-2010 Intel Corporation.  All Rights Reserved.

    This file is part of Threading Building Blocks.

    Threading Building Blocks is free software; you can redistribute it
    and/or modify it under the terms of the GNU General Public License
    version 2 as published by the Free Software Foundation.

    Threading Building Blocks is distributed in the hope that it will be
    useful, but WITHOUT ANY WARRANTY; without even the implied warranty
    of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with Threading Building Blocks; if not, write to the Free Software
    Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA

    As a special exception, you may use this file as part of a free software
    library without restriction.  Specifically, if other files instantiate
    templates or use macros or inline functions from this file, or you compile
    this file and link it with other files to produce an executable, this
    file does not by itself cause the resulting executable to be covered by
    the GNU General Public License.  This exception does not however
    invalidate any other reasons why the executable file might be covered by
    the GNU General Public License.
*/

#include "Matrix.h"
#include "tbb/atomic.h"
#include <vector>

enum OpKind {
    // Use Cell's value
    OP_VALUE,
    // Unary negation
    OP_NEGATE,
    // Addition
    OP_ADD,
    // Subtraction
    OP_SUB,
    // Multiplication
    OP_MUL
};

static const int ArityOfOp[] = {0,1,2,2,2};

class Cell {
public:
    //! Operation for this cell
    OpKind op;

    //! Inputs to this cell
    Cell* input[2];
   
    //! Type of value stored in a Cell
    typedef Matrix value_type;

    //! Value associated with this Cell
    value_type value;

    //! Set of cells that use this Cell as an input
    std::vector<Cell*> successor;

    //! Reference count of number of inputs that are not yet updated.
    tbb::atomic<int> ref_count;

    //! Update the Cell's value.
    void update();

    //! Default construtor
    Cell() {}
};

//! A directed graph where the vertices are Cells.
class Graph {
    std::vector<Cell> my_vertex_set;
public:
    //! Create a random acyclic directed graph
    void create_random_dag( size_t number_of_nodes );

    //! Print the graph
    void print();

    //! Get set of cells that have no inputs.
    void get_root_set( std::vector<Cell*>& root_set );
};