Update jacobi_mpi.cpp

lab10/jacobi/jacobi_mpi.cpp

@@ -0,0 +1,57 @@
+#include "jacobi.h"
+#include "jacobi_main.h"
+
+Result JacobiMPI::run(const Matrix& init, double epsilon, int maxNumIter){
+  int rank, numProc;
+  MPI_Comm_rank(MPI_COMM_WORLD, &rank);
+  MPI_Comm_size(MPI_COMM_WORLD, &numProc);
+
+  std::vector<Matrix> phi(2, init);
+  const int numRows = phi[0].rows();
+  const int numCols = phi[0].cols();
+  std::vector<double> halo_up(numCols);
+  std::vector<double> halo_low(numCols);
+
+  double dist = std::numeric_limits<double>::max();
+  int nIter = 0;
+
+  int t0 = 0;  // array index of current timestep
+  int t1 = 1;  // array index of next timestep
+  while (dist > epsilon && nIter < maxNumIter) {
+    dist = 0;
+
+    if (rank == 0)
+    {
+      MPI_Send(&phi[t0][numRows - 1]);
+
+      for (int i = 1; i < numRows - 1; ++i) {
+        for (int j = 1; j < numCols - 1; ++j) {
+          phi[t1](i, j) = .25 * (phi[t0](i + 1, j) + phi[t0](i - 1, j) +
+                                 phi[t0](i, j + 1) + phi[t0](i, j - 1));
+          const double diff = phi[t1](i, j) - phi[t0](i, j);
+          dist = std::max(dist, std::abs(diff));
+        }
+      }
+
+    }
+    
+
+    for (int i = 1; i < numRows - 1; ++i) {
+      for (int j = 1; j < numCols - 1; ++j) {
+        phi[t1](i, j) = .25 * (phi[t0](i + 1, j) + phi[t0](i - 1, j) +
+                               phi[t0](i, j + 1) + phi[t0](i, j - 1));
+        const double diff = phi[t1](i, j) - phi[t0](i, j);
+        dist = std::max(dist, std::abs(diff));
+      }
+    }
+
+    // if (nIter % 1000 == 0) {
+    //   std::cout << "Iteration " << nIter << ", dist=" << dist << "\n";
+    // }
+
+    nIter++;
+    std::swap(t0, t1);
+  }
+
+  return Result{phi[t0], dist, nIter};
+}