Coprocessing example

This example is used to demonstrate how the coprocessing library can be used with a simulation code.

CoProcessingExample.cxx

<source lang="cpp">

1. include "vtkCPDataDescription.h"
2. include "vtkCPInputDataDescription.h"
3. include "vtkCPProcessor.h"
4. include "vtkCPPythonScriptPipeline.h"
5. include "vtkElevationFilter.h"
6. include "vtkMultiProcessController.h"
7. include "vtkPolyData.h"
8. include "vtkSmartPointer.h"
9. include "vtkSphereSource.h"
10. include "vtkXMLUnstructuredGridReader.h"

1. include <mpi.h>
2. include <string>

class DataGenerator { public:

 DataGenerator()
   {
   this->Sphere = vtkSmartPointer<vtkSphereSource>::New();
   this->Sphere->SetThetaResolution(30);
   this->Sphere->SetPhiResolution(30);
   int procId;
   MPI_Comm_rank(MPI_COMM_WORLD, &procId);
   this->Sphere->SetCenter(procId*4.0, 0, 0);
   this->Elevation = vtkSmartPointer<vtkElevationFilter>::New();
   this->Elevation->SetInputConnection(this->Sphere->GetOutputPort());
   this->Index = 0;
   }

 vtkSmartPointer<vtkPolyData> GetNext()
   {
   double radius = fabs(sin(0.1 * this->Index));
   this->Index++;
   this->Sphere->SetRadius(1.0 + radius);
   this->Elevation->Update();
   vtkSmartPointer<vtkPolyData> ret = vtkSmartPointer<vtkPolyData>::New();
   ret->DeepCopy(this->Elevation->GetOutput());
   return ret;
   }

protected:

 int Index;
 vtkSmartPointer<vtkSphereSource> Sphere;
 vtkSmartPointer<vtkElevationFilter> Elevation;

};

int main(int argc, char* argv[]) {

 if (argc < 3)
   {
   printf("Usage: %s <cp python file> <number of steps>\n", argv[0]);
   return 1;
   }
 // we assume that this is done in parallel
 MPI_Init(&argc, &argv);

 std::string cpPythonFile = argv[1];
 int nSteps = atoi(argv[2]);

 vtkCPProcessor* processor = vtkCPProcessor::New();
 processor->Initialize();
 vtkCPPythonScriptPipeline* pipeline = vtkCPPythonScriptPipeline::New();

 // read the coprocessing python file
 if(pipeline->Initialize(cpPythonFile.c_str()) == 0)
   {
   cout << "Problem reading the python script.\n";
   return 1;
   }

 processor->AddPipeline(pipeline);
 pipeline->Delete();

 if (nSteps == 0)
   {
   return 0;
   }

 // create a data source, typically this will come from the adaptor
 // but here we use generator to create it ourselves
 DataGenerator generator;

 // do coprocessing
 double tStart = 0.0;
 double tEnd = 1.0;
 double stepSize = (tEnd - tStart)/nSteps;

 vtkCPDataDescription* dataDesc = vtkCPDataDescription::New();
 dataDesc->AddInput("input");

 for (int i = 0; i < nSteps; ++i)
   {
   double currentTime = tStart + stepSize*i;
   // set the current time and time step
   dataDesc->SetTimeData(currentTime, i);

   // check if the script says we should do coprocessing now
   if(processor->RequestDataDescription(dataDesc) != 0)
     {
     // we are going to do coprocessing so use generator to
     // create our grid at this timestep and provide it to
     // the coprocessing library
     vtkSmartPointer<vtkDataObject> dataObject =
       generator.GetNext();

     dataDesc->GetInputDescriptionByName("input")->SetGrid(dataObject);
     processor->CoProcess(dataDesc);
     }
   }

 dataDesc->Delete();
 processor->Finalize();
 processor->Delete();

 MPI_Finalize();

 return 0;

} </source>

CMakeLists.txt

<source lang="cmake"> cmake_minimum_required(VERSION 2.6)

PROJECT(CoProcessingExample)

FIND_PACKAGE(ParaView REQUIRED) INCLUDE(${PARAVIEW_USE_FILE})

FIND_PACKAGE(MPI REQUIRED) INCLUDE_DIRECTORIES(${MPI_INCLUDE_PATH})

ADD_EXECUTABLE(CoProcessingExample CoProcessingExample.cxx) TARGET_LINK_LIBRARIES(CoProcessingExample vtkCoProcessor) </source>