Coprocessing example
This example is used to demonstrate how the co-processing library can be used with a C++ based simulation code. In the ParaView/CoProcessing/Adaptors/FortranAdaptors directory there is code useful for integrating C or Fortran based simulation codes withthe co-processing library. Note that this example requires MPI to be available on your system. The executable takes in a python coprocessing script and a number of time steps to be run for. Note to remember to set your system environment properly. See [[1]] for details.
CoProcessingExample.cxx
#include "vtkCPDataDescription.h"
#include "vtkCPInputDataDescription.h"
#include "vtkCPProcessor.h"
#include "vtkCPPythonScriptPipeline.h"
#include "vtkElevationFilter.h"
#include "vtkPolyData.h"
#include "vtkSmartPointer.h"
#include "vtkSphereSource.h"
#include "vtkXMLUnstructuredGridReader.h"
#include <mpi.h>
#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 <python coprocessing script> <number of time 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;
}
CMakeLists.txt
cmake_minimum_required(VERSION 2.6)
PROJECT(CoProcessingExample)
FIND_PACKAGE(ParaView REQUIRED)
INCLUDE(${PARAVIEW_USE_FILE})
ADD_EXECUTABLE(CoProcessingExample CoProcessingExample.cxx)
TARGET_LINK_LIBRARIES(CoProcessingExample vtkCoProcessorImplementation)
Python Scripts
The first python script below is used to just output the actual results of the example. This would correspond to a simulation run with a coarse grid in order to set up coprocessing runs for larger grids where outputting the entire simulation results can be computationally prohibitive.
try: paraview.simple
except: from paraview.simple import *
def RequestDataDescription(datadescription):
"Callback to populate the request for current timestep"
timestep = datadescription.GetTimeStep()
input_name = 'input'
if (timestep % 1 == 0) :
datadescription.GetInputDescriptionByName(input_name).AllFieldsOn()
datadescription.GetInputDescriptionByName(input_name).GenerateMeshOn()
else:
datadescription.GetInputDescriptionByName(input_name).AllFieldsOff()
datadescription.GetInputDescriptionByName(input_name).GenerateMeshOff()
def DoCoProcessing(datadescription):
"Callback to do co-processing for current timestep"
cp_writers = []
timestep = datadescription.GetTimeStep()
grid = CreateProducer( datadescription, "input" )
ParallelPolyDataWriter1 = CreateWriter( XMLPPolyDataWriter, "input_grid_%t.pvtp", 1, cp_writers )
for writer in cp_writers:
if timestep % writer.cpFrequency == 0:
writer.FileName = writer.cpFileName.replace("%t", str(timestep))
writer.UpdatePipeline()
# explicitly delete the proxies -- we do it this way to avoid problems with prototypes
tobedeleted = GetNextProxyToDelete()
while tobedeleted != None:
Delete(tobedeleted)
tobedeleted = GetNextProxyToDelete()
def GetNextProxyToDelete():
proxyiterator = servermanager.ProxyIterator()
for proxy in proxyiterator:
group = proxyiterator.GetGroup()
if group.find("prototypes") != -1:
continue
if group != 'timekeeper' and group.find("pq_helper_proxies") == -1 :
return proxy
return None
def CreateProducer(datadescription, gridname):
"Creates a producer proxy for the grid"
if not datadescription.GetInputDescriptionByName(gridname):
raise RuntimeError, "Simulation input name '%s' does not exist" % gridname
grid = datadescription.GetInputDescriptionByName(gridname).GetGrid()
producer = TrivialProducer()
producer.GetClientSideObject().SetOutput(grid)
producer.UpdatePipeline()
return producer
def CreateWriter(proxy_ctor, filename, freq, cp_writers):
writer = proxy_ctor()
writer.FileName = filename
writer.add_attribute("cpFrequency", freq)
writer.add_attribute("cpFileName", filename)
cp_writers.append(writer)
return writer
This second script is still rather simple and only performs a cut on the input from the simulation code. It demonstrates though how desired results can be obtained while performing coprocessing at specified time steps.
try: paraview.simple
except: from paraview.simple import *
def RequestDataDescription(datadescription):
"Callback to populate the request for current timestep"
timestep = datadescription.GetTimeStep()
input_name = 'input'
if (timestep % 5 == 0) :
datadescription.GetInputDescriptionByName(input_name).AllFieldsOn()
datadescription.GetInputDescriptionByName(input_name).GenerateMeshOn()
else:
datadescription.GetInputDescriptionByName(input_name).AllFieldsOff()
datadescription.GetInputDescriptionByName(input_name).GenerateMeshOff()
def DoCoProcessing(datadescription):
"Callback to do co-processing for current timestep"
cp_writers = []
timestep = datadescription.GetTimeStep()
grid = CreateProducer( datadescription, "input" )
Clip2 = Clip( guiName="Clip2", InsideOut=0, UseValueAsOffset=0, Scalars=['POINTS', 'Elevation'], Value=0.0, ClipType="Plane" )
Clip2.ClipType.Normal = [0.0, 1.0, 0.0]
Clip2.ClipType.Origin = [1.9999999105930328, 0.0, 0.0]
Clip2.ClipType.Offset = 0.0
ParallelUnstructuredGridWriter2 = CreateWriter( XMLPUnstructuredGridWriter, "Cut_%t.pvtu", 5, cp_writers )
for writer in cp_writers:
if timestep % writer.cpFrequency == 0:
writer.FileName = writer.cpFileName.replace("%t", str(timestep))
writer.UpdatePipeline()
# explicitly delete the proxies -- we do it this way to avoid problems with prototypes
tobedeleted = GetNextProxyToDelete()
while tobedeleted != None:
Delete(tobedeleted)
tobedeleted = GetNextProxyToDelete()
def GetNextProxyToDelete():
proxyiterator = servermanager.ProxyIterator()
for proxy in proxyiterator:
group = proxyiterator.GetGroup()
if group.find("prototypes") != -1:
continue
if group != 'timekeeper' and group.find("pq_helper_proxies") == -1 :
return proxy
return None
def CreateProducer(datadescription, gridname):
"Creates a producer proxy for the grid"
if not datadescription.GetInputDescriptionByName(gridname):
raise RuntimeError, "Simulation input name '%s' does not exist" % gridname
grid = datadescription.GetInputDescriptionByName(gridname).GetGrid()
producer = TrivialProducer()
producer.GetClientSideObject().SetOutput(grid)
producer.UpdatePipeline()
return producer
def CreateWriter(proxy_ctor, filename, freq, cp_writers):
writer = proxy_ctor()
writer.FileName = filename
writer.add_attribute("cpFrequency", freq)
writer.add_attribute("cpFileName", filename)
cp_writers.append(writer)
return writer