# GraphAlgorithmSource

VTKExamples/Cxx/Developers/GraphAlgorithmSource

### Description

This example produces a vtkGraph as output.

### Code

GraphAlgorithmSource.cxx

    #include <vtkSmartPointer.h>
    #include <vtkGraph.h>
    #include <vtkMutableUndirectedGraph.h>

    #include "vtkTestGraphAlgorithmSource.h"

    int main (int, char *[])
    {
      vtkSmartPointer<vtkTestGraphAlgorithmSource> source =
        vtkSmartPointer<vtkTestGraphAlgorithmSource>::New();
      source->Update();

      vtkGraph* outputGraph = source->GetOutput();

      std::cout << "Output number of vertices: "
                << outputGraph->GetNumberOfVertices() << std::endl;

      return EXIT_SUCCESS;
    }

vtkTestGraphAlgorithmSource.h

    #ifndef __vtkTestGraphAlgorithmSource_h
    #define __vtkTestGraphAlgorithmSource_h

    #include <vtkGraphAlgorithm.h>

    class vtkTestGraphAlgorithmSource : public vtkGraphAlgorithm
    {
    public:
      static vtkTestGraphAlgorithmSource *New();
      vtkTypeMacro(vtkTestGraphAlgorithmSource,vtkGraphAlgorithm);
      void PrintSelf(ostream& os, vtkIndent indent);

    protected:
      vtkTestGraphAlgorithmSource();
      ~vtkTestGraphAlgorithmSource();

      int RequestData(vtkInformation *, vtkInformationVector **, vtkInformationVector *);

      int RequestDataObject(vtkInformation *, vtkInformationVector **, vtkInformationVector *);

    private:
      vtkTestGraphAlgorithmSource(const vtkTestGraphAlgorithmSource&);  // Not implemented.
      void operator=(const vtkTestGraphAlgorithmSource&);  // Not implemented.

    };

    #endif

vtkTestGraphAlgorithmSource.cxx

    #include "vtkTestGraphAlgorithmSource.h"

    #include <vtkObjectFactory.h>
    #include <vtkStreamingDemandDrivenPipeline.h>
    #include <vtkInformationVector.h>
    #include <vtkInformation.h>
    #include <vtkDataObject.h>
    #include <vtkSmartPointer.h>
    #include <vtkMutableUndirectedGraph.h>
    #include <vtkUndirectedGraph.h>
    #include <vtkGraph.h>

    vtkStandardNewMacro(vtkTestGraphAlgorithmSource);

    vtkTestGraphAlgorithmSource::vtkTestGraphAlgorithmSource()
    {
      this->SetNumberOfInputPorts(0);
      this->SetNumberOfOutputPorts(1);
    }

    vtkTestGraphAlgorithmSource::~vtkTestGraphAlgorithmSource()
    {

    }

    int vtkTestGraphAlgorithmSource::RequestData(
      vtkInformation *vtkNotUsed(request),
      vtkInformationVector **vtkNotUsed(inputVector),
      vtkInformationVector *outputVector)
    {

      vtkInformation *outInfo = outputVector->GetInformationObject(0);

      vtkGraph *output = vtkGraph::SafeDownCast(
        outInfo->Get(vtkDataObject::DATA_OBJECT()));

      vtkSmartPointer<vtkMutableUndirectedGraph> NewGraph =
        vtkSmartPointer<vtkMutableUndirectedGraph>::New();

      //add 3 vertices
      NewGraph->AddVertex();
      NewGraph->AddVertex();
      NewGraph->AddVertex();

      output->ShallowCopy(NewGraph);

      return 1;
    }

    int vtkTestGraphAlgorithmSource::RequestDataObject(
      vtkInformation*,
      vtkInformationVector**,
      vtkInformationVector* )
    {

      vtkUndirectedGraph *output = 0;
      output = vtkUndirectedGraph::New();

      this->GetExecutive()->SetOutputData(0, output);
      output->Delete();

      return 1;
    }

    //----------------------------------------------------------------------------
    void vtkTestGraphAlgorithmSource::PrintSelf(ostream& os, vtkIndent indent)
    {
      this->Superclass::PrintSelf(os,indent);
    }

### CMakeLists.txt

    cmake_minimum_required(VERSION 2.8)

    PROJECT(GraphAlgorithmSource)

    find_package(VTK REQUIRED)
    include(${VTK_USE_FILE})

    add_executable(GraphAlgorithmSource MACOSX_BUNDLE GraphAlgorithmSource.cxx  vtkTestGraphAlgorithmSource.cxx)

    target_link_libraries(GraphAlgorithmSource ${VTK_LIBRARIES})

### Download and Build GraphAlgorithmSource

Click here to download GraphAlgorithmSource and its CMakeLists.txt file. Once the tarball GraphAlgorithmSource.tar has been downloaded and extracted,

    cd GraphAlgorithmSource/build

If VTK is installed:

    cmake ..

If VTK is not installed but compiled on your system, you will need to specify the path to your VTK build:

    cmake -DVTK_DIR:PATH=/home/me/vtk_build ..

Build the project:

    make

and run it:

    ./GraphAlgorithmSource

WINDOWS USERS PLEASE NOTE: Be sure to add the VTK bin directory to your path. This will resolve the VTK dll's at run time.