How to share a string array using open mpi - c

Question

I'm new in openmpi and I don't know how to use scatter and gather to send an array of strings to all processors. I would like to divide an array and send it to each processor, but all I can divide are the characters of a single array element. Can anyone help me please?
Here is my code:
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "mpi.h"
#define MASTER 0
#define BUF_SIZE 2048
#define CHAR_SIZE 900
#define CHARS 13
#define MAX_SIZE 3500
#define NUMBER_OF_FILES 2
int main(int argc, char** argv) {
int number_of_words = 0;
int total_rows = 0;
int i, j = 0;
char **words = (char**) calloc(MAX_SIZE, sizeof (char*));
for (i = 0; i < MAX_SIZE; i++) {
words[i] = (char*) calloc(CHARS, sizeof (char));
}
char **local_words = (char**) calloc(MAX_SIZE, sizeof (char*));
for (i = 0; i < MAX_SIZE; i++) {
local_words[i] = (char*) calloc(CHARS, sizeof (char));
}
char **rec_words = (char**) calloc(MAX_SIZE, sizeof (char*));
for (i = 0; i < MAX_SIZE; i++) {
rec_words[i] = (char*) calloc(CHARS, sizeof (char));
}
char str_righe[BUF_SIZE][CHAR_SIZE];
FILE *f = NULL;
char f_title[10];
char str_nfiles[10];
char delim[10] = {10, 32, 33, 39, 44, 46, 58, 59, 63};
char *ptr;
int rank;
int size;
int message_length;
MPI_Init(&argc, &argv);
MPI_Comm_size(MPI_COMM_WORLD, &size);
MPI_Comm_rank(MPI_COMM_WORLD, &rank);
for (i = 1; i <= NUMBER_OF_FILES; i++) {
strcpy(f_title, "f");
sprintf(str_nfiles, "%d", i);
strcat(f_title, str_nfiles);
strcat(f_title, ".txt");
f = fopen(f_title, "r");
while (fgets(str_righe[j], BUF_SIZE, f)) {
str_righe[j][strlen(str_righe[j])] = '\0';
j++;
}
fclose(f);
}
total_rows = j;
for (i = 0; i < total_rows; ++i) {
ptr = strtok(str_righe[i], delim);
while (ptr != NULL) {
strcpy(words[number_of_words], ptr);
ptr = strtok(NULL, delim);
number_of_words++;
}
}
message_length = number_of_words / size;
if (rank == MASTER) {
for (i = 0; i < number_of_words; i++)
printf("%s\n", words[i]);
}
MPI_Scatter(*words, message_length, MPI_CHAR, *local_words, message_length, MPI_CHAR, MASTER, MPI_COMM_WORLD);
printf("rank %d, fragment: \t%s\n", rank, *local_words);
MPI_Gather(*local_words, message_length, MPI_CHAR, *rec_words, message_length, MPI_CHAR, MASTER, MPI_COMM_WORLD);
if (rank == MASTER) {
printf("rank %d, gathered: \t%s\n", rank, *rec_words);
}
MPI_Finalize();
return EXIT_SUCCESS;
}
I expect the output:
iMac-di-iMac01:mpi macbook$ mpirun -n 2 main
Good
time
by
antonio
rank 0, fragment: Good time
rank 1, fragment: by antonio
rank 0, gathered: Good time by antonio
But the actual output is:
iMac-di-iMac01:mpi macbook$ mpirun -n 2 main
Good
time
by
antonio
rank 0, fragment: Go
rank 1, fragment: od
rank 0, gathered: Good

Answer 1

I realized that I never shared the solution to the problem. I do it now:
I created the matrix variable and I sent the one with the scatter. In this way the slaves received the words and not the characters
int *matrix = 0;
matrix = malloc(sizeof (int) * n_words);
j = 1;
for (i = 0; i <= n_words; i++) {
matrix[i] = j;
j++;
}
n_words_cpu = n_words / (size);
procRow = malloc(sizeof (int) * n_words); // received row will contain p integers
MPI_Scatter(
/* send_data = */ matrix,
/* send_count = */ n_words_cpu,
/* send_datatype = */ MPI_INT,
/* recv_data = */ procRow,
/* recv_count = */ n_words_cpu,
/* recv_datatype = */ MPI_INT,
/* root = */ MASTER,
/* MPI_commuicator = */ MPI_COMM_WORLD);