mpi.c

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#ifdef HAVE_MPI

#include <stdbool.h>

#include <communication/mpi.h>
#include <communication/wnd.h>
#include <communication/gvt.h>
#include <communication/communication.h>
#include <queues/queues.h>
#include <core/core.h>
#include <arch/atomic.h>
#include <statistics/statistics.h>

bool mpi_support_multithread;

spinlock_t mpi_lock;

static spinlock_t msgs_lock;

static unsigned int terminated = 0;

static MPI_Request *termination_reqs;

static spinlock_t msgs_fini;

static MPI_Op reduce_stats_op;

static MPI_Datatype stats_mpi_t;

static MPI_Comm msg_comm;


bool pending_msgs(int tag)
{
    int flag = 0;
    lock_mpi();
    MPI_Iprobe(MPI_ANY_SOURCE, tag, MPI_COMM_WORLD, &flag, MPI_STATUS_IGNORE);
    unlock_mpi();
    return (bool)flag;
}

bool is_request_completed(MPI_Request *req)
{
    int flag = 0;
    lock_mpi();
    MPI_Test(req, &flag, MPI_STATUS_IGNORE);
    unlock_mpi();
    return (bool)flag;
}

void send_remote_msg(msg_t *msg)
{
    outgoing_msg *out_msg = allocate_outgoing_msg();
    out_msg->msg = msg;
    out_msg->msg->colour = threads_phase_colour[local_tid];
    unsigned int dest = find_kernel_by_gid(msg->receiver);

    register_outgoing_msg(out_msg->msg);

    lock_mpi();
    MPI_Isend(((char *)out_msg->msg) + MSG_PADDING, MSG_META_SIZE + msg->size, MPI_BYTE, dest, msg->receiver.to_int, msg_comm, &out_msg->req);
    unlock_mpi();

    // Keep the message in the outgoing queue until it will be delivered
    store_outgoing_msg(out_msg, dest);
}

void receive_remote_msgs(void)
{
    int size;
    msg_t *msg;
    MPI_Status status;
    MPI_Message mpi_msg;
    int pending;
    struct lp_struct *lp;
    GID_t gid;

    // TODO: given the latest changes in the platform, this *might*
    // be removed.
    if (!spin_trylock(&msgs_lock))
        return;

    while (true) {
        lock_mpi();
        MPI_Improbe(MPI_ANY_SOURCE, MPI_ANY_TAG, msg_comm, &pending, &mpi_msg, &status);
        unlock_mpi();

        if (!pending)
            goto out;

        MPI_Get_count(&status, MPI_BYTE, &size);

        if (likely(MSG_PADDING + size <= SLAB_MSG_SIZE)) {
            set_gid(gid, status.MPI_TAG);
            lp = find_lp_by_gid(gid);
            msg = get_msg_from_slab(lp);
        } else {
            msg = rsalloc(MSG_PADDING + size);
            bzero(msg, MSG_PADDING);
        }

        // Receive the message. Use MPI_Mrecv to be sure that the very same message
        // which was matched by the previous MPI_Improbe is extracted.
        lock_mpi();
        MPI_Mrecv(((char *)msg) + MSG_PADDING, size, MPI_BYTE, &mpi_msg, MPI_STATUS_IGNORE);
        unlock_mpi();

        validate_msg(msg);
        insert_bottom_half(msg);
    }
    out:
    spin_unlock(&msgs_lock);
}



bool all_kernels_terminated(void)
{
    return (terminated == n_ker);
}



void collect_termination(void)
{
    int res;
    unsigned int tdata;

    if (terminated == 0 || !spin_trylock(&msgs_fini))
        return;

    while (pending_msgs(MSG_FINI)) {
        lock_mpi();
        res =
            MPI_Recv(&tdata, 1, MPI_UNSIGNED, MPI_ANY_SOURCE, MSG_FINI, MPI_COMM_WORLD, MPI_STATUS_IGNORE);
        unlock_mpi();
        if (unlikely(res != 0)) {
            rootsim_error(true, "MPI_Recv did not complete correctly");
            return;
        }
        terminated++;
    }
    spin_unlock(&msgs_fini);
}


void broadcast_termination(void)
{
    unsigned int i;
    lock_mpi();
    for (i = 0; i < n_ker; i++) {
        if (i == kid)
            continue;
        MPI_Isend(&i, 1, MPI_UNSIGNED, i, MSG_FINI, MPI_COMM_WORLD, &termination_reqs[i]);
    }
    terminated++;
    unlock_mpi();
}


static void reduce_stat_vector(struct stat_t *in, struct stat_t *inout, int *len, MPI_Datatype *dptr)
{
    (void)dptr;
    int i = 0;

    for (i = 0; i < *len; ++i) {
        inout[i].vec += in[i].vec;
        inout[i].gvt_round_time += in[i].gvt_round_time;
        inout[i].gvt_round_time_min = fmin(inout[i].gvt_round_time_min, in[i].gvt_round_time_min);
        inout[i].gvt_round_time_max = fmax(inout[i].gvt_round_time_max, in[i].gvt_round_time_max);
        inout[i].max_resident_set += in[i].max_resident_set;
    }
}



#define MPI_TYPE_STAT_LEN (sizeof(struct stat_t)/sizeof(double))

static void stats_reduction_init(void)
{
    // This is a compilation time fail-safe
    static_assert(offsetof(struct stat_t, gvt_round_time_max) == (sizeof(double) * 19), "The packing assumptions on struct stat_t are wrong or its definition has been modified");

    unsigned i;

    // Boilerplate to create a new MPI data type
    MPI_Datatype type[MPI_TYPE_STAT_LEN];
    MPI_Aint disp[MPI_TYPE_STAT_LEN];
    int block_lengths[MPI_TYPE_STAT_LEN];

    // Initialize those arrays (we asssume that struct stat_t is packed tightly)
    for (i = 0; i < MPI_TYPE_STAT_LEN; ++i) {
        type[i] = MPI_DOUBLE;
        disp[i] = i * sizeof(double);
        block_lengths[i] = 1;
    }

    // Create the custom type and commit the changes
    MPI_Type_create_struct(MPI_TYPE_STAT_LEN, block_lengths, disp, type, &stats_mpi_t);
    MPI_Type_commit(&stats_mpi_t);

    // Create the MPI Operation used to reduce stats
    if (master_thread()) {
        MPI_Op_create((MPI_User_function *)reduce_stat_vector, true, &reduce_stats_op);
    }
}

#undef MPI_TYPE_STAT_LEN


void mpi_reduce_statistics(struct stat_t *global, struct stat_t *local)
{
    MPI_Reduce(local, global, 1, stats_mpi_t, reduce_stats_op, 0, MPI_COMM_WORLD);
}



void dist_termination_init(void)
{
    /* init for collective termination */
    termination_reqs = rsalloc(n_ker * sizeof(MPI_Request));
    unsigned int i;
    for (i = 0; i < n_ker; i++) {
        termination_reqs[i] = MPI_REQUEST_NULL;
    }
    spinlock_init(&msgs_fini);
}



void dist_termination_finalize(void)
{
    MPI_Waitall(n_ker, termination_reqs, MPI_STATUSES_IGNORE);
}

void syncronize_all(void)
{
    if (master_thread()) {
        MPI_Comm comm;
        MPI_Comm_dup(MPI_COMM_WORLD, &comm);
        MPI_Barrier(comm);
        MPI_Comm_free(&comm);
    }
    thread_barrier(&all_thread_barrier);
}


void mpi_init(int *argc, char ***argv)
{
    int mpi_thread_lvl_provided = 0;
    MPI_Init_thread(argc, argv, MPI_THREAD_MULTIPLE, &mpi_thread_lvl_provided);

    mpi_support_multithread = true;
    if (mpi_thread_lvl_provided < MPI_THREAD_MULTIPLE) {
        //MPI do not support thread safe api call
        if (mpi_thread_lvl_provided < MPI_THREAD_SERIALIZED) {
            // MPI do not even support serialized threaded call we cannot continue
            rootsim_error(true, "The MPI implementation does not support threads [current thread level support: %d]\n", mpi_thread_lvl_provided);
        }
        mpi_support_multithread = false;
    }

    spinlock_init(&mpi_lock);

    MPI_Comm_size(MPI_COMM_WORLD, (int *)&n_ker);
    MPI_Comm_rank(MPI_COMM_WORLD, (int *)&kid);

    // Create a separate communicator which we use to send event messages
    MPI_Comm_dup(MPI_COMM_WORLD, &msg_comm);
}


void inter_kernel_comm_init(void)
{
    spinlock_init(&msgs_lock);

    outgoing_window_init();
    gvt_comm_init();
    dist_termination_init();
    stats_reduction_init();
}


void inter_kernel_comm_finalize(void)
{
    dist_termination_finalize();
    //outgoing_window_finalize();
    gvt_comm_finalize();
}


void mpi_finalize(void)
{
    if (master_thread()) {
        MPI_Barrier(MPI_COMM_WORLD);
        MPI_Comm_free(&msg_comm);
        MPI_Finalize();
    } else {
        rootsim_error(true, "MPI finalize has been invoked by a non master thread: T%u\n", local_tid);
    }
}

#endif /* HAVE_MPI */