static shell_state
grid_next_handle()
{
if (!grid_next())
{
printf("No more packets captured\n");
}
return GRID;
}
int main(int arg_c, char* arg_v[]){
//initialize mpi
MPI_Init(&arg_c, &arg_v);
if(arg_c != 5){
std::cout << "usage: D (diffusion parameter) L (size of quadrant) N (#steps in 1 dimension) dt (timestep)" << std::endl;
return 1;
}
double D = std::stod(arg_v[1]);
double L = std::stod(arg_v[2]);
int N = std::stoi(arg_v[3]);
double dt = std::stod(arg_v[4]);
int n, rank;
//get the mpi parameters n and rank
MPI_Comm_size(MPI_COMM_WORLD, &n);
MPI_Comm_rank(MPI_COMM_WORLD, &rank);
if(rank == 0)
std::cout << "mpi version with " << n << " 'threads'." << std::endl;
// slice the grid into parts and give the parts to the solvers
// create the grid-part!
int sliceHeight = 2*N / n;
double x,y;
double dxy = L/N;
std::vector<std::vector<double>> grid(sliceHeight);
std::vector<std::vector<double>> grid_next(sliceHeight);
for(int i = 0; i<sliceHeight; i++){
x = dxy * (i+rank*sliceHeight-N);
grid[i] = std::vector<double> (2*N+1);
grid_next[i] = std::vector<double> (2*N+1);
for(int j = 0; j<=N*2; j++){
y = dxy * (j-N);
if(std::sqrt(x*x + y*y) < 0.5)
grid[i][j] = 1;
}
}
double tmax = 10000 * dt;
double tcurrent = 0;
double y_part, x_part;
timer t;
t.start();
while(tcurrent < tmax){
tcurrent += dt;
// do the communication
// solve that part
for(int i=1; i<sliceHeight-1; i++){
for(int j=0; j<=2*N; j++){
x_part = grid[i+1][j] - 2*grid[i][j] + grid[i-1][j];
x_part = x_part / dxy;
y_part = ((j==2*N)?0.0:grid[i][j+1]) - 2*grid[i][j] +
((j==0)?0.0:grid[i][j-1]);
y_part = y_part / dxy;
grid_next[i][j] = dt * D * (x_part + y_part) + grid[i][j];
}
}
//do the corner-cases
//swap
std::swap(grid, grid_next);
}
t.stop();
std::cout << "in rank " << rank << " time passed: " << t.get_timing();
MPI_Finalize();
return 0;
}
