Sheet 7

sheet7/E5678/main.cpp

@@ -0,0 +1,136 @@
+
+#include <iostream>                               // MPI
+#include <mpi.h>
+#include <vector>
+using namespace std;
+
+
+void DebugVector(vector<double> const& xin, MPI_Comm const& icomm)
+{
+  int myrank, numprocs;
+   
+   MPI_Comm_rank(icomm, &myrank);                          
+   MPI_Comm_size(icomm, &numprocs);
+   int selectedProcess = 0;
+    while(selectedProcess >= 0 && selectedProcess < numprocs)
+    {
+      if(myrank == 0)
+      {
+        cout << "Enter process number: " << endl;
+        cin >> selectedProcess;
+
+      }
+
+      MPI_Bcast(&selectedProcess, 1, MPI_INT, 0, icomm);
+      MPI_Barrier(icomm);
+      if(myrank == selectedProcess )
+      {
+        for(double x : xin)
+        {
+          cout << x << " ";
+        }
+        cout << endl;
+      }
+      MPI_Barrier(icomm);
+
+    }
+}
+
+double par_scalar(const vector<double>& x, const vector<double>& y, MPI_Comm icomm) {
+ 
+    double local = 0.0;
+    for (unsigned int i = 0; i < x.size(); ++i) {
+        local += x[i] * y[i];
+    }
+
+    double sum = 0.0;
+    MPI_Allreduce(&local, &sum, 1, MPI_DOUBLE, MPI_SUM, icomm);
+
+    return sum;
+}
+
+void E7(const vector<double>& x, MPI_Comm comm,
+                             double& min, double& max)
+{
+    double local_min = x[0];
+    double local_max = x[0];
+
+    for (double x_i : x) {
+        if (x_i < local_min)
+        {
+          local_min = x_i;
+        } 
+        if (x_i> local_max) 
+        {
+          local_max = x_i;
+        }
+
+    }
+
+    MPI_Allreduce(&local_min, &min, 1, MPI_DOUBLE, MPI_MIN, comm);
+    MPI_Allreduce(&local_max, &max, 1, MPI_DOUBLE, MPI_MAX, comm);
+}
+
+
+int main(int argc, char *argv[])
+{
+    MPI_Comm icomm = MPI_COMM_WORLD;
+    MPI_Init(&argc, &argv);
+    int myrank, numprocs;
+    //numprocs = 1;    // delete this line when uncommenting the next line
+   MPI_Comm_rank(icomm, &myrank);                          // my MPI-rank
+   MPI_Comm_size(icomm, &numprocs);
+
+   if (0==myrank) {
+     cout << "\n There are " << numprocs << " processes running.\n \n";
+   }
+
+
+    if (0==myrank) cout << endl;
+
+    unsigned int n=20;
+    vector<double> x(n);
+    vector<double> y(n);
+    double x_i;
+    
+    for(unsigned int i=0; i<n; i++)
+    {
+      x_i = myrank*100+(i%5)*10+i;
+      x[i] = x_i;
+
+      if(myrank == 0 && i == 0)
+      {
+        y[i] = 0.0;
+      }
+      else{
+        y[i] = 1.0/x_i;
+      }
+      
+    }
+
+    DebugVector(x,icomm);
+
+    double result = par_scalar(x,y,icomm);
+
+    if(myrank == 0)
+    {
+       cout << "result scalar: " << result << endl;
+    }
+   
+    double min, max;
+    E7(x,icomm,min,max);
+    if(myrank == 0)
+    {
+       cout << "min: " << min << ", max: "<< max << endl;
+    }
+
+
+    
+    MPI_Alltoall(MPI_IN_PLACE, 0, MPI_DOUBLE, x.data(), 5, MPI_DOUBLE, icomm);
+    DebugVector(x,icomm);
+
+    MPI_Finalize();
+    return 0;
+}
+
+