MPI and MemoryLeaks and MPI_Wait() with async send and recv

Question

I am new to MPI programming and I am trying to create a program that would perform 2-way communication between processes in a ring.

I was getting MemoryLeaks errors at the MPI_Finalize() statement. Later I found out that I could use the -fsanitize=address -fno-omit-frame-pointer flags to help me debug where the leaks could be.

Now I get a very bizarre (at least for me) error.

Here's my code:

        MPI_Request request_s1, request_s2, request_r1, request_r2;

        // receiving 2 elems from the left neighbor, which i shall be needing
        if (0 > MPI_Irecv(lefties, EXTENT, MPI_DOUBLE, my_left, 1, MPI_COMM_WORLD, &request_r1)) {
            return 2;
        }

        // receiving 2 elems from my right neighbor which i will be appending at the end of my input
        if (0 > MPI_Irecv(righties, EXTENT, MPI_DOUBLE, my_right, 1, MPI_COMM_WORLD, &request_r2)) {
            return 2;
        }

        // sending the first 2 elems which will be required by the left neighbor
        if (0 > MPI_Isend(my_output_buffer, EXTENT, MPI_DOUBLE, my_left, 1, MPI_COMM_WORLD, &request_s1)) {
            return 2;
        }

        // sending the last 2 elems to my right neighbor
        if (0 > MPI_Isend(&my_output_buffer[displacement - EXTENT], EXTENT, MPI_DOUBLE, my_right, 1, MPI_COMM_WORLD, &request_s2)) {
            return 2;
        }

        MPI_Wait(&request_r2, MPI_STATUS_IGNORE);
        MPI_Wait(&request_r1, MPI_STATUS_IGNORE);

The error I get is

[my_machine:18353] *** An error occurred in MPI_Wait
[my_machine:18359] *** reported by process [204079105,1]
[my_machine:18359] *** on communicator MPI_COMM_WORLD
[my_machine:18359] *** MPI_ERR_TRUNCATE: message truncated
[my_machine:18359] *** MPI_ERRORS_ARE_FATAL (processes in this communicator will now abort,
[my_machine:18359] ***    and potentially your MPI job)
[my_machine:18353] 1 more process has sent help message help-mpi-btl-base.txt / btl:no-nics
[my_machine:18353] Set MCA parameter "orte_base_help_aggregate" to 0 to see all help / error messages

and I have no clue how to progress from here.

Answer 1

1. You seem to be reusing your request variables. Don't. If one is created, you have to wait for it.
2. It wouldn't hurt to initialize the request variables with MPI_REQUEST_NULL, in case you're waiting for a request that was not created.
3. The 0>MPI_whatever idiom is strange. Instead: MPI_SUCCESS!=MPI_Whatever.
4. But even that may not be work because the default is that routines do not return on error, but abort the program.
5. And it may be something else entirely which I can't tell without seeing the rest of the code.