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Sheet 7 (7_3)

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Georg Thomas Mandl 2026-01-07 01:00:22 +01:00
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Sheet_7/bsp_7_3/main.cpp Normal file
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// MPI code in C++.
// See [Gropp/Lusk/Skjellum, "Using MPI", p.33/41 etc.]
// and /opt/mpich/include/mpi2c++/comm.h for details
#include "vec_func.h"
#include <iostream> // MPI
#include <mpi.h>
using namespace std;
int main(int argc, char *argv[])
{
MPI_Comm icomm = MPI_COMM_WORLD;
MPI_Init(&argc, &argv);
int myrank;
MPI_Comm_rank(icomm, &myrank);
// E5
vector<double> x(10,3);
if(myrank==0) {cout << endl << "E5" << endl;}
vecdebug(x, icomm);
// E6
vector<double> y(10,1.0/3);
double res = par_scalar(x,y,icomm);
if(myrank==0)
{
cout << endl << endl << "E6" << endl;
cout << "<x,y> = " << res << endl << endl;
}
// E7
vector<double> a{myrank*10, myrank*10-1, myrank*10-2};
if(myrank==0) {cout << "E7\n" << "original vector" << endl;}
vecdebug(a, icomm);
double min_val, max_val;
min_max_exch(a, min_val, max_val, icomm);
if(myrank==0) {cout << "min = " << min_val << "\tmax = " << max_val << endl << endl << "vector after changing min-max" << endl;}
vecdebug(a, icomm);
// E8
int n = 20;
vector<double> c(n);
for(size_t i=0; i<n; ++i)
{
c[i] = myrank*100 +(i%5)*10+i;
}
vector<double> recv(n);
MPI_Alltoall(c.data(), 5, MPI_DOUBLE, recv.data(), 5, MPI_DOUBLE, icomm);
if(myrank==0) {cout << endl << "Ex 8\n" << "Alltoall" << endl;}
vecdebug(recv, icomm);
MPI_Alltoall(MPI_IN_PLACE, 0, MPI_DATATYPE_NULL, c.data(), 5, MPI_DOUBLE, icomm);
if(myrank==0) {cout << endl << "Ex 8\n" << "Alltoall - IN_PLACE" << endl;}
vecdebug(c, icomm);
MPI_Finalize();
return 0;
}