mpi.cpp

#include <mpi.h>

main() {
    int my_rank, num_proc;
    int a, b, i;        // it depends
    
    
}

openmpi_localvar.cpp

main() {
  // *** part 0 *** //
  float x, a[100], b[100];
  int i, p, lb, ub, nprocs;
  
  MPI_Comm_rank(MPI_COMM_WORLD, &id);
  MPI_Comm_size(MPI_COMM_WORLD, &nprocs);
  
  // *** part I *** //
  if (0 == id) {
    // send appropriate portions of arrays a and b to all other procs.
    for (p = 1; p < nprocs; p ++) {
      lb = p * 100 / nprocs;
      MPI_Send(&(a[lb]), 100 / nprocs, MPI_FLOAT, p, ...);
      MPI_Send(&(b[lb]), 100 / nprocs, MPI_FLOAT, p, ...);
      
    }
  } else {
    // receive portion of arrays from proc 0
    MPI_Recv(&a, 100 / nprocs, MPI_FLOAT, 0, ...);
    MPI_Recv(&b, 100 / nprocs, MPI_FLOAT, 0, ...);
  }
  
  // *** part II *** //
  for (i = 0; i < 100 / nprocs, i ++) {
    x = powf(a[i], 3);
    b[i] = x * b[i];
  }
  
  // *** part III *** //
  if (0 == id) {
    for (p - 1, p < nprocs, p ++) {
      lb = p * 100 / nprocs;
      MPI_Recv(&b[lb], ...);
    }
  } else {
    MPI_Send(&b, 100 / nprocs, ...);
  }
}

openmpi_loop_carried_dep.cpp

// 详细参考Lecture 16, Page 25:26
main () {
    
    // 略
    
    offset = id * 100 / nprocs;
    
    for (i = 0; i < 100 / nprocs; i ++) {   // everyone only work on 100 / nprocs number of data.
        i1 = i + offset;
        indx = (i1 * (i1 + 1) / 2);
        a[i] = b[indx];                     // when finish there will have a[0:24]
    }
    
    // 略
}

openmpi_pi.cpp

// OpenMPI for PI computation
// Example of CS546
#include "mpi.h"
#include <cmath>
#include <cstdio>

int main(int argc, char* argv[1]) {
	int done = 0, n, myid, proc, i, rc;
	double PI25DT = 3.1415926	// value of PI
	double mypi, pi, width, sum, x, a;

	// Initialization
	MPI_Init(&argc, &argv);
	MPI_Comm_Size(MPI_COMM_WORLD, &numproc);
	MPI_Comm_Rank(MPI_COMM_WORLD, &myid);

	// Computation
	while(!done) {
		if (0 == myid) {
			printf("Enter the number of intervals (0 quits):");
			scanf("%d", &n);
		}
		MPI_Bcast(&n, 1, MPI_INT, 0, MPI_COMM_WORLD);
		if (0 == n) { break; }

		width = 1.0 / (double) n;
		sum = 0.0;
		for (i = myid ++; i <= n; i += numproc) {
			x = width * ((double)i - 0.5);
			sum += 4.0 / (1.0 + x * x);
			mypi = sum * width;
		}

		
		MPI_Reduce(&mypi, &pi, MPI_DOUBLE, MPI_SUM, 0, MPI_COMM_WORLD);
		
		if (0 == myid) {
			printf("pi is approximately ...");
		}
	}
	
	MPI_Finalize();
	return;
}

openmpi_static_blocked_scheduling_alt.cpp

// 略 详见 Lecture 16, Page 34:35

// *** part I *** //
MPI_Scatter(&b, 100, MPI_INT, &bmp, 100 / nprocs, ...);     // TODO
MPI_Scatter(&c, ...);                                       // TODO

// *** part II *** //
for (i = 0; i < 100 / nprocs; i ++) {
    a[i] = b[i] * c[i];
}

// *** part III *** //
MPI_Gather(...);                                            // TODO

openmpi_sum_reduction.cpp

// 详细参考 Lecture 16, Page 28:29

main () {
    // 略
    
    // *** step II *** //
    sub_total = 0;
    
    for (i = 0; i < 100 / nprocs; i ++) {
        sub_total = a[i];
    }
    
    if (0 == id) {
        lb = xxx;           // TODO
        MPI_Recv();    // TODO
    } else {
        MPI_Send();    // TODO
    }
    
    MPI_Reduce(&sub_total, total, ..., SUM, 0, ...);    // TODO
}

openmpi_type_struct.cpp

// for Lecture 17 Page 21

int blockcounts[4] = [50, 1, 4, 2];

MPI_Datatype types[4];
MPI_Int disps[4];
MPI_Datatype cmdtype;

MPI_Address (&cmdline.display, &disps[0]);
MPI_Address (&cmdline.max, &disps[1]);
MPI_Address (&cmdline.xmin, &disps[2]);
MPI_Address (&cmdline.width, &disps[3]);
MPI_Address (&cmdline + 1, ..., &disps[4]); // ?

types[0] = MPI_CHAR;
types[1] = MPI_INT;
types[2] = MPI_DOUBLE;
types[3] = MPI_INT;
types[4] = MPI_UB;

for (int i = 4; i >= 0; i --) {
    disps[i] -= disps[0];
}

MPI_Type_Struct(5, blockcount, disps, types, &cmdtype);
MPI_Type_Commit(&cmdtype);

openmpi_VECTOR.cpp

// for Lecture 17 Page 18

MPI_Type_vector(5, 1, 7, MPI_INT, newtype);

MPI_Send(&a, 1, newtype);