TNL::Graphs::GraphVertexView< MatrixView, Orientation > Struct Template Reference

View type for accessing individual graph vertices and their edges. More...

Detailed Description

template<typename MatrixView, typename Orientation>
struct TNL::Graphs::GraphVertexView< MatrixView, Orientation >

View type for accessing individual graph vertices and their edges.

GraphVertexView provides access to a single vertex (node) in a graph, allowing iteration over its edges, accessing edge weights, and modifying edge properties. It is similar to a matrix row view but provides graph-specific interface methods.

The GraphVertexView is typically obtained from a Graph using methods like getVertex() or during parallel traversal with forAllVertices(). It wraps either a dense or sparse matrix row view, depending on the underlying adjacency matrix type.

Template Parameters

MatrixView	Type of the underlying matrix view (DenseMatrixView or SparseMatrixView).
Orientation	Graph orientation (DirectedGraph or UndirectedGraph).

Example

#include <iostream>
#include <TNL/Graphs/Graph.h>
#include <TNL/Graphs/traverse.h>
#include <TNL/Containers/Array.h>
#include <TNL/Devices/Host.h>
#include <TNL/Devices/Cuda.h>
#include <TNL/Devices/Hip.h>
 
template< typename Device >
void
vertexViewExample()
{
   using GraphType = TNL::Graphs::Graph< float, Device, int, TNL::Graphs::DirectedGraph >;
 
   /***
    * Create a directed graph
    */
   // clang-format off
   GraphType graph( 5,
        {  { 0, 1, 10.0 }, { 0, 2, 20.0 },
                           { 1, 2, 30.0 }, { 1, 3, 40.0 }, { 1, 4, 50.0 },
                                           { 2, 3, 60.0 },
           { 3, 0, 70.0 },                                 { 3, 4, 80.0 },
           { 4, 0, 90.0 } } );
   // clang-format on
 
   std::cout << "Graph:\n" << graph << '\n';
 
   /***
    * Modifying edge weights using forAllVertices
    */
   std::cout << "\nExample 3: Modifying edge weights\n";
 
   TNL::Graphs::forAllVertices(
      graph,
      [] __cuda_callable__( typename GraphType::VertexView vertex )
      {
         for( int i = 0; i < vertex.getDegree(); i++ ) {
            vertex.setEdgeWeight( i, vertex.getEdgeWeight( i ) + 1.0 );
         }
      } );
 
   std::cout << "Graph after modifying edge weights:\n" << graph << '\n';
}
 
int
main( int argc, char* argv[] )
{
   std::cout << "Running on host:\n";
   vertexViewExample< TNL::Devices::Host >();
 
#ifdef __CUDACC__
   std::cout << "Running on CUDA device:\n";
   vertexViewExample< TNL::Devices::Cuda >();
#endif
 
#ifdef __HIP__
   std::cout << "Running on HIP device:\n";
   vertexViewExample< TNL::Devices::Hip >();
#endif
 
   return EXIT_SUCCESS;
}

Output

Running on host:
Graph:
Row: 0 ->     1:10      2:20  
Row: 1 ->     2:30      3:40      4:50  
Row: 2 ->     3:60  
Row: 3 ->     0:70      4:80  
Row: 4 ->     0:90  
 
 
Example 3: Modifying edge weights
Graph after modifying edge weights:
Row: 0 ->     1:11      2:21  
Row: 1 ->     2:31      3:41      4:51  
Row: 2 ->     3:61  
Row: 3 ->     0:71      4:81  
Row: 4 ->     0:91  
 
Running on CUDA device:
Graph:
Row: 0 ->     1:10      2:20  
Row: 1 ->     2:30      3:40      4:50  
Row: 2 ->     3:60  
Row: 3 ->     0:70      4:80  
Row: 4 ->     0:90  
 
 
Example 3: Modifying edge weights
Graph after modifying edge weights:
Row: 0 ->     1:11      2:21  
Row: 1 ->     2:31      3:41      4:51  
Row: 2 ->     3:61  
Row: 3 ->     0:71      4:81  
Row: 4 ->     0:91  
 

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The documentation for this struct was generated from the following file:

• src/TNL/Graphs/GraphVertexView.h