I'm trying to create a log file from each processor and then send that to the root as a char array. I first send the length and then I send the data. The length sends fine, but the data is always garbage! Here is my code:
MPI_Barrier (MPI_COMM_WORLD);
string out = "";
MPI_Status status[2];
MPI_Request reqs[num_procs];
string log = "TEST";
int length = log.length();
char* temp = (char *) malloc(length+1);
strcpy(temp, log.c_str());
if (my_id != 0)
{
MPI_Send (&length, 1, MPI_INT, 0, 1, MPI_COMM_WORLD);
MPI_Send (&temp, length+1, MPI_CHAR, 0, 1, MPI_COMM_WORLD);
}
else {
int length;
for (int i = 1; i < num_procs; i++)
{
MPI_Recv (&length, 2, MPI_INT, i, 1, MPI_COMM_WORLD, &status[0]);
char* rec_buf;
rec_buf = (char *) malloc(length+1);
MPI_Recv (rec_buf, length+1, MPI_CHAR, i, 1, MPI_COMM_WORLD, &status[1]);
out += rec_buf;
free(rec_buf);
}
}
MPI_Barrier (MPI_COMM_WORLD);
free(temp);
You are passing a char**
to MPI_Send
instead of a char*
this causes memory corruption, or in your case the garbled output you are getting. Everything should be fine if you use
MPI_Send (temp, length+1, MPI_CHAR, 0, 1, MPI_COMM_WORLD);
(note the removed &
in front of the first argument, temp
.)
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