/* -*- Mode: C; c-basic-offset:4 ; indent-tabs-mode:nil ; -*- */
/*
* (C) 2003 by Argonne National Laboratory.
* See COPYRIGHT in top-level directory.
*/
/* MPI-3 distributed linked list construction example
* --------------------------------------------------
*
* Construct a distributed shared linked list using proposed MPI-3 dynamic
* windows. Initially process 0 creates the head of the list, attaches it to
* the window, and broadcasts the pointer to all processes. Each process p then
* appends N new elements to the list when the tail reaches process p-1.
*/
#include <stdio.h>
#include <stdlib.h>
#include <mpi.h>
#include <assert.h>
#include "mpitest.h"
#ifdef HAVE_UNISTD_H
#include <unistd.h>
#endif
#define NUM_ELEMS 1000
#define MAX_NPROBE nproc
#define MIN_NPROBE 1
#define ELEM_PER_ROW 16
#define MIN(X,Y) ((X < Y) ? (X) : (Y))
#define MAX(X,Y) ((X > Y) ? (X) : (Y))
/* Linked list pointer */
typedef struct {
int rank;
MPI_Aint disp;
} llist_ptr_t;
/* Linked list element */
typedef struct {
int value;
llist_ptr_t next;
} llist_elem_t;
static const llist_ptr_t nil = { -1, (MPI_Aint) MPI_BOTTOM };
static const int verbose = 0;
static const int print_perf = 0;
/* List of locally allocated list elements. */
static llist_elem_t **my_elems = NULL;
static int my_elems_size = 0;
static int my_elems_count = 0;
/* Allocate a new shared linked list element */
MPI_Aint alloc_elem(int value, MPI_Win win)
{
MPI_Aint disp;
llist_elem_t *elem_ptr;
/* Allocate the new element and register it with the window */
MPI_Alloc_mem(sizeof(llist_elem_t), MPI_INFO_NULL, &elem_ptr);
elem_ptr->value = value;
elem_ptr->next = nil;
MPI_Win_attach(win, elem_ptr, sizeof(llist_elem_t));
/* Add the element to the list of local elements so we can free it later. */
if (my_elems_size == my_elems_count) {
my_elems_size += 100;
my_elems = realloc(my_elems, my_elems_size * sizeof(void *));
}
my_elems[my_elems_count] = elem_ptr;
my_elems_count++;
MPI_Get_address(elem_ptr, &disp);
return disp;
}
int main(int argc, char **argv)
{
int procid, nproc, i, j, my_nelem;
int pollint = 0;
double time;
MPI_Win llist_win;
llist_ptr_t head_ptr, tail_ptr;
int errs = 0;
MTest_Init(&argc, &argv);
MPI_Comm_rank(MPI_COMM_WORLD, &procid);
MPI_Comm_size(MPI_COMM_WORLD, &nproc);
MPI_Win_create_dynamic(MPI_INFO_NULL, MPI_COMM_WORLD, &llist_win);
/* Process 0 creates the head node */
if (procid == 0)
head_ptr.disp = alloc_elem(procid, llist_win);
/* Broadcast the head pointer to everyone */
head_ptr.rank = 0;
MPI_Bcast(&head_ptr.disp, 1, MPI_AINT, 0, MPI_COMM_WORLD);
tail_ptr = head_ptr;
/* All processes append NUM_ELEMS elements to the list; rank 0 has already
* appended an element. */
if (procid == 0)
i = 1;
else
i = 0;
my_nelem = NUM_ELEMS / nproc;
if (procid < NUM_ELEMS % nproc)
my_nelem++;
MPI_Barrier(MPI_COMM_WORLD);
time = MPI_Wtime();
/* Lock the window for shared access to all targets */
MPI_Win_lock_all(0, llist_win);
for (; i < my_nelem; i++) {
llist_ptr_t new_elem_ptr;
int success = 0;
MTEST_VG_MEM_INIT(&new_elem_ptr, sizeof(llist_ptr_t));
/* Create a new list element and register it with the window */
new_elem_ptr.rank = procid;
new_elem_ptr.disp = alloc_elem(procid, llist_win);
/* Append the new node to the list. This might take multiple attempts if
* others have already appended and our tail pointer is stale. */
do {
int flag;
/* The tail is at my left neighbor, append my element. */
if (tail_ptr.rank == (procid + nproc - 1) % nproc) {
if (verbose)
printf("%d: Appending to <%d, %p>\n", procid, tail_ptr.rank,
(void *) tail_ptr.disp);
#if 1
MPI_Accumulate(&new_elem_ptr, sizeof(llist_ptr_t), MPI_BYTE, tail_ptr.rank,
(MPI_Aint) & (((llist_elem_t *) tail_ptr.disp)->next),
sizeof(llist_ptr_t), MPI_BYTE, MPI_REPLACE, llist_win);
#else
MPI_Put(&new_elem_ptr, sizeof(llist_ptr_t), MPI_BYTE, tail_ptr.rank,
(MPI_Aint) & (((llist_elem_t *) tail_ptr.disp)->next), sizeof(llist_ptr_t),
MPI_BYTE, llist_win);
#endif
MPI_Win_flush(tail_ptr.rank, llist_win);
success = 1;
tail_ptr = new_elem_ptr;
}
/* Otherwise, chase the tail. */
else {
llist_ptr_t next_tail_ptr;
MPI_Get_accumulate(NULL, 0, MPI_DATATYPE_NULL, &next_tail_ptr,
sizeof(llist_ptr_t), MPI_BYTE, tail_ptr.rank,
(MPI_Aint) & (((llist_elem_t *) tail_ptr.disp)->next),
sizeof(llist_ptr_t), MPI_BYTE, MPI_NO_OP, llist_win);
MPI_Win_flush(tail_ptr.rank, llist_win);
if (next_tail_ptr.rank != nil.rank) {
if (verbose)
printf("%d: Chasing to <%d, %p>\n", procid, next_tail_ptr.rank,
(void *) next_tail_ptr.disp);
tail_ptr = next_tail_ptr;
pollint = MAX(MIN_NPROBE, pollint / 2);
} else {
for (j = 0; j < pollint; j++)
MPI_Iprobe(MPI_ANY_SOURCE, MPI_ANY_TAG, MPI_COMM_WORLD, &flag,
MPI_STATUS_IGNORE);
pollint = MIN(MAX_NPROBE, pollint * 2);
}
}
} while (!success);
}
MPI_Win_unlock_all(llist_win);
MPI_Barrier(MPI_COMM_WORLD);
time = MPI_Wtime() - time;
/* Traverse the list and verify that all processes inserted exactly the correct
* number of elements. */
if (procid == 0) {
int *counts, count = 0;
counts = (int *) malloc(sizeof(int) * nproc);
assert(counts != NULL);
for (i = 0; i < nproc; i++)
counts[i] = 0;
tail_ptr = head_ptr;
MPI_Win_lock_all(0, llist_win);
/* Walk the list and tally up the number of elements inserted by each rank */
while (tail_ptr.disp != nil.disp) {
llist_elem_t elem;
MPI_Get(&elem, sizeof(llist_elem_t), MPI_BYTE,
tail_ptr.rank, tail_ptr.disp, sizeof(llist_elem_t), MPI_BYTE, llist_win);
MPI_Win_flush(tail_ptr.rank, llist_win);
tail_ptr = elem.next;
assert(elem.value >= 0 && elem.value < nproc);
counts[elem.value]++;
count++;
if (verbose) {
int last_elem = tail_ptr.disp == nil.disp;
printf("%2d%s", elem.value, last_elem ? "" : " -> ");
if (count % ELEM_PER_ROW == 0 && !last_elem)
printf("\n");
}
}
MPI_Win_unlock_all(llist_win);
if (verbose)
printf("\n\n");
/* Verify the counts we collected */
for (i = 0; i < nproc; i++) {
int expected;
expected = NUM_ELEMS / nproc;
if (i < NUM_ELEMS % nproc)
expected++;
if (counts[i] != expected) {
printf("Error: Rank %d inserted %d elements, expected %d\n", i, counts[i],
expected);
errs++;
}
}
free(counts);
}
if (print_perf) {
double max_time;
MPI_Reduce(&time, &max_time, 1, MPI_DOUBLE, MPI_MAX, 0, MPI_COMM_WORLD);
if (procid == 0) {
printf("Total time = %0.2f sec, elem/sec = %0.2f, sec/elem = %0.2f usec\n", max_time,
NUM_ELEMS / max_time, max_time / NUM_ELEMS * 1.0e6);
}
}
MPI_Win_free(&llist_win);
/* Free all the elements in the list */
for (; my_elems_count > 0; my_elems_count--)
MPI_Free_mem(my_elems[my_elems_count - 1]);
MTest_Finalize(errs);
return MTestReturnValue(errs);
}