osrm-backend/DataStructures/DynamicGraph.h

/*
    open source routing machine
    Copyright (C) Dennis Luxen, others 2010

This program is free software; you can redistribute it and/or modify
it under the terms of the GNU AFFERO General Public License as published by
the Free Software Foundation; either version 3 of the License, or
any later version.

This program 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 Affero General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
or see http://www.gnu.org/licenses/agpl.txt.
*/

#ifndef DYNAMICGRAPH_H_INCLUDED
#define DYNAMICGRAPH_H_INCLUDED

#include <vector>
#include <algorithm>

#include "../typedefs.h"

// returns the smallest power of two that is at least as large as x
static unsigned log2Rounded32( unsigned x ) {
    const unsigned bitPosition[32] = {
            0, 1, 28, 2, 29, 14, 24, 3, 30, 22, 20, 15, 25, 17, 4, 8,
            31, 27, 13, 23, 21, 19, 16, 7, 26, 12, 18, 6, 11, 5, 10, 9
    };

    //round up
    --x;
    x |= x >> 1;
    x |= x >> 2;
    x |= x >> 4;
    x |= x >> 8;
    x |= x >> 16;
    ++x;
    //x is now a power of 2

    //each power of two is mapped to a unique 5 bit sequence with ( x * 0x077CB531U ) >> 27
    return bitPosition[( x * 0x077CB531U ) >> 27];
}
/*
static unsigned log2Rounded64( unsigned long long x ) {
	int upperLog = log2Rounded32( x >> 32 );
	if ( upperLog > 0 )
		return upperLog;
	return log2Rounded32( x );
}
 */

template< typename EdgeData>
class DynamicGraph {
public:
    typedef NodeID NodeIterator;
    typedef NodeID EdgeIterator;

    class InputEdge {
    public:
        EdgeData data;
        NodeIterator source;
        NodeIterator target;
        bool operator<( const InputEdge& right ) const {
            if ( source != right.source )
                return source < right.source;
            return target < right.target;
        }
    };

    DynamicGraph( int nodes, std::vector< InputEdge > &graph ) {

        std::sort( graph.begin(), graph.end() );
        _numNodes = nodes;
        _numEdges = ( EdgeIterator ) graph.size();
        _nodes.resize( _numNodes );
        EdgeIterator edge = 0;
        EdgeIterator position = 0;
        for ( NodeIterator node = 0; node < _numNodes; ++node ) {
            EdgeIterator lastEdge = edge;
            while ( edge < _numEdges && graph[edge].source == node ) {
                ++edge;
            }
            _nodes[node].firstEdge = position;
            _nodes[node].edges = edge - lastEdge;
            _nodes[node].size = 1 << log2Rounded32( edge - lastEdge );
            position += _nodes[node].size;
        }
        _edges.resize( position );
        edge = 0;
        for ( NodeIterator node = 0; node < _numNodes; ++node ) {
            for ( EdgeIterator i = _nodes[node].firstEdge, e = _nodes[node].firstEdge + _nodes[node].edges; i != e; ++i ) {
                _edges[i].target = graph[edge].target;
                _edges[i].data = graph[edge].data;
                assert(_edges[i].data.distance > 0);
                edge++;
            }
        }
    }

    unsigned GetNumberOfNodes() const {
        return _numNodes;
    }

    unsigned GetNumberOfEdges() const {
        return _numEdges;
    }

    unsigned GetOutDegree( const NodeIterator &n ) const {
        return _nodes[n].edges;
    }

    NodeIterator GetTarget( const EdgeIterator &e ) const {
        return NodeIterator( _edges[e].target );
    }

    EdgeData &GetEdgeData( const EdgeIterator &e ) {
        return _edges[e].data;
    }

    const EdgeData &GetEdgeData( const EdgeIterator &e ) const {
        return _edges[e].data;
    }

    EdgeIterator BeginEdges( const NodeIterator &n ) const {
        //assert( EndEdges( n ) - EdgeIterator( _nodes[n].firstEdge ) <= 100 );
        return EdgeIterator( _nodes[n].firstEdge );
    }

    EdgeIterator EndEdges( const NodeIterator &n ) const {
        return EdgeIterator( _nodes[n].firstEdge + _nodes[n].edges );
    }

    //adds an edge. Invalidates edge iterators for the source node
    EdgeIterator InsertEdge( const NodeIterator &from, const NodeIterator &to, const EdgeData &data ) {
        _StrNode &node = _nodes[from];
        if ( node.edges + 1 >= node.size ) {
            node.size *= 2;
            EdgeIterator newFirstEdge = ( EdgeIterator ) _edges.size();
            _edges.resize( _edges.size() + node.size );
            for ( unsigned i = 0; i < node.edges; ++i ) {
                _edges[newFirstEdge + i ] = _edges[node.firstEdge + i];
            }
            node.firstEdge = newFirstEdge;
        }
        _StrEdge &edge = _edges[node.firstEdge + node.edges];
        edge.target = to;
        edge.data = data;
        _numEdges++;
        node.edges++;
        return EdgeIterator( node.firstEdge + node.edges );
    }

    //removes an edge. Invalidates edge iterators for the source node
    void DeleteEdge( const NodeIterator source, const EdgeIterator &e ) {
        _StrNode &node = _nodes[source];
        --_numEdges;
        --node.edges;
        const unsigned last = node.firstEdge + node.edges;
        //swap with last edge
        _edges[e] = _edges[last];
    }

    //removes all edges (source,target)
    int DeleteEdgesTo( const NodeIterator source, const NodeIterator target ) {
        int deleted = 0;
        for ( EdgeIterator i = BeginEdges( source ), iend = EndEdges( source ); i < iend - deleted; ++i ) {
            if ( _edges[i].target == target ) {
                do {
                    deleted++;
                    _edges[i] = _edges[iend - deleted];
                } while ( i < iend - deleted && _edges[i].target == target );
            }
        }

#pragma omp atomic
        _numEdges -= deleted;
        _nodes[source].edges -= deleted;

        return deleted;
    }

    //searches for a specific edge
    EdgeIterator FindEdge( const NodeIterator &from, const NodeIterator &to ) const {
        EdgeIterator smallestEdge = SPECIAL_EDGEID;
        EdgeWeight smallestWeight = UINT_MAX;
        for ( EdgeIterator edge = BeginEdges( from ); edge < EndEdges(from); edge++ )
        {
            const NodeID target = GetTarget(edge);
            const EdgeWeight weight = GetEdgeData(edge).distance;
            {
                if(target == to && weight < smallestWeight)
                {
                    smallestEdge = edge; smallestWeight = weight;
                }
            }
        }
        return smallestEdge;
    }


private:

    struct _StrNode {
        //index of the first edge
        EdgeIterator firstEdge;
        //amount of edges
        unsigned edges;
        unsigned size;
    };

    struct _StrEdge {
        NodeID target;
        EdgeData data;
    };

    NodeIterator _numNodes;
    EdgeIterator _numEdges;

    std::vector< _StrNode > _nodes;
    std::vector< _StrEdge > _edges;
};

#endif // DYNAMICGRAPH_H_INCLUDED