Hi niners, I have a different query today, this relates to my master's work rather than my job. Not sure if anyone here is familiar with MPI but here it goes, I have this:

MPI_Init(&argc, &argv);
MPI_Comm_rank(MPI_COMM_WORLD, &my_rank);
MPI_Comm_size(MPI_COMM_WORLD, &comm_sz);
if(my_rank == 0) {
for(i=1; i<=n;++i)
a[i-1] = i-1;
// Distribute
MPI_Send(a, n, MPI_INT, my_rank+1, n, MPI_COMM_WORLD);
} else {
// Receive and distribute initial values
MPI_Recv(a, n, MPI_INT, MPI_ANY_SOURCE, MPI_ANY_TAG, MPI_COMM_WORLD, &status);
k = status.MPI_TAG/2;
if(k!=0) {
MPI_Send(a+1, k, MPI_INT, my_rank+1, k, MPI_COMM_WORLD); //pass sub-array [1..k]
MPI_Send(a+k+1, k, MPI_INT, k+my_rank+1, k, MPI_COMM_WORLD); //pass sub-array [k+1..2k+1]
}
partial = a[0];
printf("rank: %d\tvalue: %d\n", my_rank, partial);
// Carry out Prefix Sum algorithm : for 1 to log2(n) - THIS IS WHERE IT FAILS
j = (int)(log((float)n+1)/log((float)2));
//printf("Log(n) = %d\n", j);
for(i=0; i<j; ++i) {
k = (int)(pow((float)2,(float)i));
printf("**rank: %d, k=%d\n", my_rank, k);
if(my_rank+k<=n) MPI_Send(&partial, 1, MPI_INT, my_rank+k, 0, MPI_COMM_WORLD/*, &request*/);
if(my_rank-k>=1) {
MPI_Recv(&value, 1 , MPI_INT, my_rank-k, 0, MPI_COMM_WORLD, &status);
partial += value;
}
}
printf("rank: %d\tpartial: %d\n", my_rank, partial);
}
MPI_Finalize();

And it's deadlocking. It works about 80% of the time and the other time, it fails. I've noticed that when it fails, a process usually sends messages, ends before its receiver has received yet. Does anyone know if an MPI process can send message and finalize before message is received?

I can't see why it's deadlocking, any ideas?