I am using MPI to run a program in parallel and measure the execution time. I am currently splitting the computation between each process by giving a start and end index as a parameter in the "voxelise" function. This will then work on different sections of the data set and store the result in "p_voxel_data".
I then want to send all of these sub arrays to the root process using "MPI_Gather" so the data can be written to a file and the timer stopped.
The program executes fine when i have the "MPI_Gather" line commented out, i get output similar to this:
Computing time: NODE 3 = 1.07 seconds.
Computing time: NODE 2 = 1.12 seconds.
But when that line is included i get
"APPLICATION TERMINATED WITH THE EXIT STRING: Segmentation fault (signal 11)
And also the computing time for the root node 0 shows up as a minus number "-1.40737e+08" Can anyone suggest any issues in my call to MPI_Gather?
int main(int argc, char** argv)
//-----------------------------
{
int rank;
int nprocs;
MPI_Comm comm;
MPI::Init(argc, argv);
MPI_Comm_size(MPI_COMM_WORLD, &nprocs);
MPI_Comm_rank(MPI_COMM_WORLD, &rank);
/* Set up data for voxelise function */
. . . . . .
clock_t start(clock());
// Generate the density field
voxelise(density_function,
a,
b,
p_control_point_set,
p_voxel_data,
p_number_of_voxel,
p_voxel_size,
p_centre,
begin,
endInd );
std::vector<float> completeData(512);
std::vector<float> cpData(toProcess);
std::copy(p_voxel_data.begin() + begin, p_voxel_data.begin() + endInd, cpData.begin());
MPI_Gather(&cpData, toProcess, MPI::FLOAT, &completeData, toProcess, MPI::FLOAT, 0, MPI_COMM_WORLD);
// Stop the timer
clock_t end(clock());
float number_of_seconds(float(end - start) / CLOCKS_PER_SEC);
std::cout << "Computing time:\t" << "NODE " << rank << " = " << number_of_seconds << " seconds." <<std::endl;
if(rank == 0) {
MPI::Finalize();
return (EXIT_SUCCESS);
}
