Miscellany

#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 = 30;                      // horyzon nsteps  double time = 0.1, tau = 0.001;  int i;  double k = 0.13;                // 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++;   printf ("%d %d\n", myid, ncur - 2);  a = (double *) calloc (ncur, sizeof (double));  b = (double *) 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(ncur - 2 > 0) {        if ((ncur == 3) && (myid != 0) && (myid != numprocs - 1) || (ncur > 3) && (myid != 0)) {      b[1] = a[1] + k * tau / h / h * (a[2] + a[0] - 2 * a[1]);    }    printf ("b[1]=%f ", b[1]);}    if(ncur - 2 > 2) {    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(ncur - 2 > 0) {    if ((ncur == 3) && (myid != 0) && (myid != numprocs - 1) || (ncur > 3) && (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 ", ncur - 2, b[ncur - 2]);}        printf("\n");    c = a; a = b; b = c;  }printf ("\n");      MPI_Finalize();  return EXIT_SUCCESS;}