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#include <mpi.h>#include <stdio.h>#include <string.h>#include <stdlib.h>int main(int argc, char *argv[]){  char idstr[32];  char buff[128];  int numprocs;  int myid;  double *a, *b, *c;  int n = 6;                      // horyzon nsteps  double time = 1.0, tau = 0.001;  int i;  double k = 0.06;                // heat conduction  double h = 1.0 / (n - 1);       // horyzon step  int remain;  int ncur;                    // num of horyzon points in cur proc  MPI_Status stat;   MPI_Init (&argc, &argv);   MPI_Comm_size (MPI_COMM_WORLD, &numprocs);   MPI_Comm_rank (MPI_COMM_WORLD, &myid);     ncur = n / numprocs;  remain = n - numprocs * ncur;  ncur += 2;  while (remain--)    if (remain == myid)      ncur++;  h = 1.0 / (ncur - 2 - 1);   printf ("%d %d\n", myid, ncur - 2);  a = calloc (ncur, sizeof (double));  b = calloc (ncur, sizeof (double));  bzero (a, ncur * sizeof (double));  bzero (b, ncur * sizeof (double));  if (myid == numprocs - 1) {    a[ncur - 2] = 1.0;    b[ncur - 2] = 1.0;  }        while ((time -= tau) > 0) {    printf ("time=%f ", time);    if (!(myid % 2)) {      if (myid != numprocs - 1)        MPI_Send (&a[ncur - 2], 1, MPI_DOUBLE, myid + 1, 0, MPI_COMM_WORLD);      if (myid != 0)        MPI_Send (&a[1], 1, MPI_DOUBLE, myid - 1, 0, MPI_COMM_WORLD);      if (myid != numprocs - 1)        MPI_Recv (&a[ncur - 1], 1, MPI_DOUBLE, myid + 1, 0, MPI_COMM_WORLD, &stat);      if (myid != 0)        MPI_Recv (&a[0], 1, MPI_DOUBLE, myid - 1, 0, MPI_COMM_WORLD, &stat);    }    else {      if (myid != 0)        MPI_Recv (&a[0], 1, MPI_DOUBLE, myid - 1, 0, MPI_COMM_WORLD, &stat);      if (myid != numprocs - 1)        MPI_Recv (&a[ncur - 1], 1, MPI_DOUBLE, myid + 1, 0, MPI_COMM_WORLD, &stat);      if (myid != 0)        MPI_Send (&a[1], 1, MPI_DOUBLE, myid - 1, 0, MPI_COMM_WORLD);      if (myid != numprocs - 1)        MPI_Send (&a[ncur - 2], 1, MPI_DOUBLE, myid + 1, 0, MPI_COMM_WORLD);    }        printf ("runk=%d ", myid);        if (myid != 0)      b[1] = a[1] + k * tau / h / h * (a[2] + a[0] - 2 * a[1]);    printf ("b[1]=%f ", b[1]);        for (i = 2; i < ncur - 2; ++i) {      b[i] = a[i] + k * tau / h / h * (a[i + 1] + a[i - 1] - 2 * a[i]);      printf ("b[%d]=%f ", i, b[i]);    }        if (myid != numprocs - 1)      b[ncur - 2] = a[ncur - 2] + k * tau / h / h * (a[ncur - 1] + a[ncur - 3] - 2 * a[ncur - 2]);    printf ("b[%d]=%f\n", ncur - 2, b[ncur - 2]);        c = a; a = b; b = c;  }      MPI_Finalize();  return EXIT_SUCCESS;}