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mpi_interface.cpp
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#include "mpi_interface.h"
using namespace std;
GridTopology::GridTopology(int order){
reorder = order;
}
void GridTopology::CreateTopology(int Nx, int Ny, double hy, double hx, double Ly, double Lx){
periods.resize(2);
coords.resize(2);
dims.resize(2);
periods[0] = 1;
periods[1] = 1;
MPI_Comm_size(MPI_COMM_WORLD,&nproc);
MPI_Dims_create(nproc,2,&dims[0]);
MPI_Cart_create(MPI_COMM_WORLD,2,&dims[0],&periods[0],reorder,&comm2d);
MPI_Cart_get(comm2d,2,&dims[0],&periods[0],&coords[0]);
//Get number of cells in each process, and define local coordinates
if(coords[0] == 0){
y_dim = Ny - (dims[0]-1)*(Ny/dims[0]);
hy_vec_local.allocate(y_dim);
std::cout << hy_vec_local.GetRows() << " " << hy_vec_local.GetCols() << std::endl;
for (int i = 0; i < y_dim; i++){
hy_vec_local(i) = -Ly+(static_cast<double>(i)+0.5)*hy;
}
}
else{
y_dim = Ny/dims[0];
hy_vec_local.allocate(y_dim);
for (int i = 0; i < y_dim; i++){
int offset = (Ny - (dims[0]-1)*(Ny/dims[0])) + y_dim*(coords[0]-1);
hy_vec_local(i) = -Ly+static_cast<double>(offset)*hy + (static_cast<double>(i)+0.5)*hy;
}
}
if(coords[1] == 0){
x_dim = Nx - (dims[1]-1)*(Nx/dims[1]);
hx_vec_local.allocate(x_dim);
for (int i = 0; i < x_dim; i++){
hx_vec_local(i) = -Lx+(static_cast<double>(i)+0.5)*hx;
}
}
else{
x_dim = Nx/dims[1];
hx_vec_local.allocate(x_dim);
for (int i = 0; i < x_dim; i++){
int offset = (Nx - (dims[1]-1)*(Nx/dims[1])) + x_dim*(coords[1]-1);
hx_vec_local(i) = -Lx+static_cast<double>(offset)*hx + (static_cast<double>(i)+0.5)*hx;
}
}
//Get current process id
MPI_Comm_rank(comm2d,&myid);
//Get neighboring process ids
MPI_Cart_shift(comm2d,0,1,&lower,&upper);
MPI_Cart_shift(comm2d,1,1,&left,&right);
//Allocate array for conjugate gradient
p.allocate(y_dim+2,x_dim+2);
}
void GridTopology::GetDisplacements(int Ny, int Nx){
local_disp = 0;
if(coords[1] > 0){
local_disp = (Nx - (dims[1] - 1)*(Nx/dims[1])) + (coords[1] - 1)*(Nx/dims[1]);
}
if(coords[0] > 0){
local_disp = local_disp + (Ny - (dims[0] - 1)*(Ny/dims[0]))*Nx + (coords[0] - 1)*(Ny/dims[0])*Nx;
}
if(myid == 0){
disps.resize(nproc);
counts.resize(nproc);
counts.assign(nproc,1);
}
MPI_Gather(&local_disp,1,MPI_INT,&disps[0],1,MPI_INT,0,comm2d);
}
void GridTopology::GetFullArray(matrix & FullArray, matrix & SubArray, int Ny, int Nx){
int begin = 0;
int extent = sizeof(double);
MPI_Datatype subarray;
MPI_Datatype resized_subarray;
vector<int> dims_full_array(2);
vector<int> dims_subarray(2);
vector<int> starts(2);
starts[0] = 0;
starts[1] = 0;
dims_full_array[0] = Ny;
dims_full_array[1] = Nx;
dims_subarray[0] = y_dim;
dims_subarray[1] = x_dim;
int dims = 2;
MPI_Type_create_subarray(dims,&dims_full_array[0],&dims_subarray[0],&starts[0],MPI_ORDER_C,MPI_DOUBLE,&subarray);
MPI_Type_commit(&subarray);
MPI_Type_create_resized(subarray, begin, extent, &resized_subarray);
MPI_Type_commit(&resized_subarray);
MPI_Gatherv(&SubArray(0,0),x_dim*y_dim,MPI_DOUBLE,&FullArray(0,0),&counts[0],&disps[0],
resized_subarray,0,comm2d);
}
void Neighbors(matrix & A, GridTopology & Grid){
int x_dim = Grid.x_dim;
int y_dim = Grid.y_dim;
MPI_Status status;
//Send upper and lower ghost cells
MPI_Sendrecv(&A(y_dim,1),x_dim,MPI_DOUBLE,Grid.upper,0,&A(0,1),x_dim,MPI_DOUBLE,Grid.lower,0,Grid.comm2d,&status);
MPI_Sendrecv(&A(1,1),x_dim,MPI_DOUBLE,Grid.lower,0,&A(y_dim+1,1),x_dim,MPI_DOUBLE,Grid.upper,0,Grid.comm2d,&status);
//Left and right ghost cells
MPI_Datatype Column;
MPI_Type_vector(Grid.y_dim,1,Grid.x_dim+2,MPI_DOUBLE,&Column);
MPI_Type_commit(&Column);
MPI_Sendrecv(&A(1,1),1,Column,Grid.left,1,&A(1,Grid.x_dim+1),1,Column,Grid.right,1,Grid.comm2d,&status);
MPI_Type_vector(Grid.y_dim,1,Grid.x_dim+2,MPI_DOUBLE,&Column);
MPI_Type_commit(&Column);
MPI_Sendrecv(&A(1,Grid.x_dim),1,Column,Grid.right,1,&A(1,0),1,Column,Grid.left,1,Grid.comm2d,&status);
}
void ConjGrad(matrix & x, matrix & f, int M, int N, double hx, double hy, double dt, GridTopology & Grid){
matrix r(M,N);
////matrix p(M+2,N+2);
matrix q(M,N);
x = 0.0;
r = f;
////p = r;
Grid.p = 0.0;
vector<int> startsI(2);
vector<int> startsJ(2);
startsI[0] = 1; startsI[1] = 0;
startsJ[0] = 1; startsJ[1] = 0;
Grid.p.SetArray(r, startsI, startsJ, M, N);
Grid.rold = SumMat(r*r,M,N);
MPI_Allreduce(&Grid.rold,&Grid.rold_tot,1,MPI_DOUBLE,MPI_SUM,Grid.comm2d);
std::cout << "rold is " << Grid.rold << std::endl;
double tol = 0.001;
int k=1;
for (k = 0; k < pow(M,2); k++){
Neighbors(Grid.p,Grid);
//The commented block below was for zero Dirichlet boundary conditions.
//We're using periodic BCs in both directions
//matrix Top = (Grid.p.GetSubArray(1,1,1,N))*-1.0;
//matrix Bottom = (Grid.p.GetSubArray(M,1,1,N))*-1.0;
//matrix Left = (Grid.p.GetSubArray(1,1,M,1))*-1.0;
//matrix Right = (Grid.p.GetSubArray(1,N,M,1))*-1.0;
//Grid.p.SetRow(Top,0,1,N);
//Grid.p.SetRow(Bottom,M+1,1,N);
//Grid.p.SetCol(Left,1,0,M);
//Grid.p.SetCol(Right,1,N+1,M);
MatMult(q,Grid.p,M,N,hx,hy,dt);
matrix p_sub = Grid.p.GetSubArray(1,1,M,N);
Grid.gamma = SumMat(q*p_sub,M,N);
MPI_Allreduce(&Grid.gamma,&Grid.gamma_tot,1,MPI_DOUBLE,MPI_SUM,Grid.comm2d);
Grid.alpha_tot = Grid.rold_tot/Grid.gamma_tot;
matrix p_alpha = Grid.p*Grid.alpha_tot;
vector<int> startI(3);
vector<int> startJ(3);
startI[0] = 0; startI[1] = 0; startI[2] = 1;
startJ[0] = 0; startJ[1] = 0; startJ[2] = 1;
x.Add(x,p_alpha,startI,startJ,M,N);
r -= q*Grid.alpha_tot;
//r.Subtract(r,q,startI,startJ,M,N);
Grid.rnew = SumMat(r*r,M,N);
MPI_Allreduce(&Grid.rnew,&Grid.rnew_tot,1,MPI_DOUBLE,MPI_SUM,Grid.comm2d);
std::cout << "rnew_tot " << Grid.rnew_tot << " " << k << std::endl;
if (sqrt(Grid.rnew_tot) < tol){
break;
}
matrix p_r = Grid.p*(Grid.rnew_tot/Grid.rold_tot);
startI[0] = 1; startI[1] = 0; startI[2] = 1;
startJ[0] = 1; startJ[1] = 0; startJ[2] = 1;
Grid.p.Add(r,p_r,startI,startJ,M,N);
Grid.rold_tot=Grid.rnew_tot;
}
}
void GetGridDims(int Ny, int & y_dim, int nproc, int myid){
if(myid == 0){
y_dim = Ny - (nproc-1)*(Ny/nproc);
}
else{
y_dim = Ny/nproc;
}
}
void GetNeighbors(int & lower, int & upper, int nproc, int myid){
if(nproc == 1){
lower = 0;
upper = 0;
}
else{
if(myid == 0){
lower = nproc - 1;
upper = myid+1;
}
else if(myid == nproc-1){
lower = myid-1;
upper = 0;
}
else{
lower = myid - 1;
upper = myid+1;
}
}
}