mpispike.cpp

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#include <../../nrnconf.h>
#include <stdio.h>
#include <stdlib.h>
#include <stddef.h>
#include <assert.h>
 
/* do not want the redef in the dynamic load case */
#include <nrnmpiuse.h>
 
#if NRNMPI_DYNAMICLOAD
#include <nrnmpi_dynam.h>
#endif
 
#include <nrnmpi.h>
#include <hocdec.h>
 
#if NRNMPI
#include "nrnmpidec.h"
#include "nrnmpi_impl.h"
#include "mpispike.h"
#include <mpi.h>
 
extern void nrnbbs_context_wait();
 
static int np;
static int* displs;
static int* byteovfl; /* for the compressed transfer method */
static MPI_Datatype spike_type;
 
static void pgvts_op(double* in, double* inout, int* len, MPI_Datatype* dptr);
static MPI_Op mpi_pgvts_op;
 
static void make_spike_type() {
    NRNMPI_Spike s;
    int block_lengths[2];
    MPI_Aint displacements[2];
    MPI_Aint addresses[3];
    MPI_Datatype typelist[2];
 
    typelist[0] = MPI_INT;
    typelist[1] = MPI_DOUBLE;
 
    block_lengths[0] = block_lengths[1] = 1;
 
    MPI_Get_address(&s, &addresses[0]);
    MPI_Get_address(&(s.gid), &addresses[1]);
    MPI_Get_address(&(s.spiketime), &addresses[2]);
 
    displacements[0] = addresses[1] - addresses[0];
    displacements[1] = addresses[2] - addresses[0];
 
    MPI_Type_create_struct(2, block_lengths, displacements, typelist, &spike_type);
    MPI_Type_commit(&spike_type);
 
    MPI_Op_create((MPI_User_function*) pgvts_op, 1, &mpi_pgvts_op);
}
 
void nrnmpi_spike_initialize() {
    make_spike_type();
}
 
#if nrn_spikebuf_size > 0
 
static MPI_Datatype spikebuf_type;
 
static void make_spikebuf_type() {
    NRNMPI_Spikebuf s;
    int block_lengths[3];
    MPI_Aint displacements[3];
    MPI_Aint addresses[4];
    MPI_Datatype typelist[3];
 
    typelist[0] = MPI_INT;
    typelist[1] = MPI_INT;
    typelist[2] = MPI_DOUBLE;
 
    block_lengths[0] = 1;
    block_lengths[1] = nrn_spikebuf_size;
    block_lengths[2] = nrn_spikebuf_size;
 
    MPI_Get_address(&s, &addresses[0]);
    MPI_Get_address(&(s.nspike), &addresses[1]);
    MPI_Get_address(&(s.gid[0]), &addresses[2]);
    MPI_Get_address(&(s.spiketime[0]), &addresses[3]);
 
    displacements[0] = addresses[1] - addresses[0];
    displacements[1] = addresses[2] - addresses[0];
    displacements[2] = addresses[3] - addresses[0];
 
    MPI_Type_create_struct(3, block_lengths, displacements, typelist, &spikebuf_type);
    MPI_Type_commit(&spikebuf_type);
}
#endif
 
int nrnmpi_spike_exchange() {
    int i, n, novfl, n1;
    if (!displs) {
        np = nrnmpi_numprocs;
        displs = (int*) hoc_Emalloc(np * sizeof(int));
        hoc_malchk();
        displs[0] = 0;
#if nrn_spikebuf_size > 0
        make_spikebuf_type();
#endif
    }
    nrnbbs_context_wait();
#if nrn_spikebuf_size == 0
    MPI_Allgather(&nout_, 1, MPI_INT, nin_, 1, MPI_INT, nrnmpi_comm);
    n = nin_[0];
    for (i = 1; i < np; ++i) {
        displs[i] = n;
        n += nin_[i];
    }
    if (n) {
        if (icapacity_ < n) {
            icapacity_ = n + 10;
            free(spikein_);
            spikein_ = (NRNMPI_Spike*) hoc_Emalloc(icapacity_ * sizeof(NRNMPI_Spike));
            hoc_malchk();
        }
        MPI_Allgatherv(
            spikeout_, nout_, spike_type, spikein_, nin_, displs, spike_type, nrnmpi_comm);
    }
#else
    MPI_Allgather(spbufout_, 1, spikebuf_type, spbufin_, 1, spikebuf_type, nrnmpi_comm);
    novfl = 0;
    n = spbufin_[0].nspike;
    if (n > nrn_spikebuf_size) {
        nin_[0] = n - nrn_spikebuf_size;
        novfl += nin_[0];
    } else {
        nin_[0] = 0;
    }
    for (i = 1; i < np; ++i) {
        displs[i] = novfl;
        n1 = spbufin_[i].nspike;
        n += n1;
        if (n1 > nrn_spikebuf_size) {
            nin_[i] = n1 - nrn_spikebuf_size;
            novfl += nin_[i];
        } else {
            nin_[i] = 0;
        }
    }
    if (novfl) {
        if (icapacity_ < novfl) {
            icapacity_ = novfl + 10;
            free(spikein_);
            spikein_ = (NRNMPI_Spike*) hoc_Emalloc(icapacity_ * sizeof(NRNMPI_Spike));
            hoc_malchk();
        }
        n1 = (nout_ > nrn_spikebuf_size) ? nout_ - nrn_spikebuf_size : 0;
        MPI_Allgatherv(spikeout_, n1, spike_type, spikein_, nin_, displs, spike_type, nrnmpi_comm);
    }
    ovfl_ = novfl;
#endif
    return n;
}
 
/*
The compressed spike format is restricted to the fixed step method and is
a sequence of unsigned char.
nspike = buf[0]*256 + buf[1]
a sequence of spiketime, localgid pairs. There are nspike of them.
    spiketime is relative to the last transfer time in units of dt.
    note that this requires a mindelay < 256*dt.
    localgid is an unsigned int, unsigned short,
    or unsigned char in size depending on the range and thus takes
    4, 2, or 1 byte respectively. To be machine independent we do our
    own byte coding. When the localgid range is smaller than the true
    gid range, the gid->PreSyn are remapped into
    hostid specific maps. If there are not many holes, i.e just about every
    spike from a source machine is delivered to some cell on a
    target machine, then instead of a hash map, a vector is used.
The allgather sends the first part of the buf and the allgatherv buffer
sends any overflow.
*/
int nrnmpi_spike_exchange_compressed() {
    int i, novfl, n, ntot, idx, bs, bstot; /* n is #spikes, bs is #byte overflow */
    if (!displs) {
        np = nrnmpi_numprocs;
        displs = (int*) hoc_Emalloc(np * sizeof(int));
        hoc_malchk();
        displs[0] = 0;
    }
    if (!byteovfl) {
        byteovfl = (int*) hoc_Emalloc(np * sizeof(int));
        hoc_malchk();
    }
    nrnbbs_context_wait();
 
    MPI_Allgather(
        spfixout_, ag_send_size_, MPI_BYTE, spfixin_, ag_send_size_, MPI_BYTE, nrnmpi_comm);
    novfl = 0;
    ntot = 0;
    bstot = 0;
    for (i = 0; i < np; ++i) {
        displs[i] = bstot;
        idx = i * ag_send_size_;
        n = spfixin_[idx++] * 256;
        n += spfixin_[idx++];
        ntot += n;
        nin_[i] = n;
        if (n > ag_send_nspike_) {
            bs = 2 + n * (1 + localgid_size_) - ag_send_size_;
            byteovfl[i] = bs;
            bstot += bs;
            novfl += n - ag_send_nspike_;
        } else {
            byteovfl[i] = 0;
        }
    }
    if (novfl) {
        if (ovfl_capacity_ < novfl) {
            ovfl_capacity_ = novfl + 10;
            free(spfixin_ovfl_);
            spfixin_ovfl_ = (unsigned char*) hoc_Emalloc(ovfl_capacity_ * (1 + localgid_size_) *
                                                         sizeof(unsigned char));
            hoc_malchk();
        }
        bs = byteovfl[nrnmpi_myid];
        /*
        note that the spfixout_ buffer is one since the overflow
        is contiguous to the first part. But the spfixin_ovfl_ is
        completely separate from the spfixin_ since the latter
        dynamically changes its size during a run.
        */
        MPI_Allgatherv(spfixout_ + ag_send_size_,
                       bs,
                       MPI_BYTE,
                       spfixin_ovfl_,
                       byteovfl,
                       displs,
                       MPI_BYTE,
                       nrnmpi_comm);
    }
    ovfl_ = novfl;
    return ntot;
}
 
double nrnmpi_mindelay(double m) {
    double result;
    if (!nrnmpi_use) {
        return m;
    }
    nrnbbs_context_wait();
    MPI_Allreduce(&m, &result, 1, MPI_DOUBLE, MPI_MIN, nrnmpi_comm);
    return result;
}
 
int nrnmpi_int_allmax(int x) {
    int result;
    if (nrnmpi_numprocs < 2) {
        return x;
    }
    nrnbbs_context_wait();
    MPI_Allreduce(&x, &result, 1, MPI_INT, MPI_MAX, nrnmpi_comm);
    return result;
}
 
#define ALLTOALLV_SPARSE_TAG 101980
 
/* Code derived from MPI_Alltoallv_sparse in MP-Gadget: https://github.com/MP-Gadget */
 
static int MPI_Alltoallv_sparse(void* sendbuf,
                                int* sendcnts,
                                int* sdispls,
                                MPI_Datatype sendtype,
                                void* recvbuf,
                                int* recvcnts,
                                int* rdispls,
                                MPI_Datatype recvtype,
                                MPI_Comm comm) {
    int status;
    int myrank;
    int nranks;
    status = MPI_Comm_rank(comm, &myrank);
    assert(status == MPI_SUCCESS);
    status = MPI_Comm_size(comm, &nranks);
    assert(status == MPI_SUCCESS);
 
    int rankp;
    for (rankp = 0; nranks > (1 << rankp); rankp++)
        ;
 
    ptrdiff_t lb;
    ptrdiff_t send_elsize;
    ptrdiff_t recv_elsize;
 
    status = MPI_Type_get_extent(sendtype, &lb, &send_elsize);
    assert(status == MPI_SUCCESS);
    status = MPI_Type_get_extent(recvtype, &lb, &recv_elsize);
    assert(status == MPI_SUCCESS);
 
    MPI_Request* requests = (MPI_Request*) hoc_Emalloc(nranks * 2 * sizeof(MPI_Request));
    hoc_malchk();
    assert(requests != NULL);
 
    int ngrp;
    int n_requests;
    n_requests = 0;
    for (ngrp = 0; ngrp < (1 << rankp); ngrp++) {
        int target = myrank ^ ngrp;
 
        if (target >= nranks)
            continue;
        if (recvcnts[target] == 0)
            continue;
        status = MPI_Irecv((static_cast<char*>(recvbuf)) + recv_elsize * rdispls[target],
                           recvcnts[target],
                           recvtype,
                           target,
                           ALLTOALLV_SPARSE_TAG,
                           comm,
                           &requests[n_requests++]);
        assert(status == MPI_SUCCESS);
    }
 
    status = MPI_Barrier(comm);
    assert(status == MPI_SUCCESS);
 
    for (ngrp = 0; ngrp < (1 << rankp); ngrp++) {
        int target = myrank ^ ngrp;
        if (target >= nranks)
            continue;
        if (sendcnts[target] == 0)
            continue;
        status = MPI_Isend((static_cast<char*>(sendbuf)) + send_elsize * sdispls[target],
                           sendcnts[target],
                           sendtype,
                           target,
                           ALLTOALLV_SPARSE_TAG,
                           comm,
                           &requests[n_requests++]);
        assert(status == MPI_SUCCESS);
    }
 
    status = MPI_Waitall(n_requests, requests, MPI_STATUSES_IGNORE);
    assert(status == MPI_SUCCESS);
    free(requests);
 
    status = MPI_Barrier(comm);
    assert(status == MPI_SUCCESS);
 
    return MPI_SUCCESS;
}
 
 
extern void nrnmpi_dbl_alltoallv_sparse(double* s,
                                        int* scnt,
                                        int* sdispl,
                                        double* r,
                                        int* rcnt,
                                        int* rdispl) {
    MPI_Alltoallv_sparse(s, scnt, sdispl, MPI_DOUBLE, r, rcnt, rdispl, MPI_DOUBLE, nrnmpi_comm);
}
extern void nrnmpi_int_alltoallv_sparse(int* s,
                                        int* scnt,
                                        int* sdispl,
                                        int* r,
                                        int* rcnt,
                                        int* rdispl) {
    MPI_Alltoallv_sparse(s, scnt, sdispl, MPI_INT, r, rcnt, rdispl, MPI_INT, nrnmpi_comm);
}
 
extern void nrnmpi_long_alltoallv_sparse(int64_t* s,
                                         int* scnt,
                                         int* sdispl,
                                         int64_t* r,
                                         int* rcnt,
                                         int* rdispl) {
    MPI_Alltoallv_sparse(s, scnt, sdispl, MPI_INT64_T, r, rcnt, rdispl, MPI_INT64_T, nrnmpi_comm);
}
 
 
extern void nrnmpi_int_gather(int* s, int* r, int cnt, int root) {
    MPI_Gather(s, cnt, MPI_INT, r, cnt, MPI_INT, root, nrnmpi_comm);
}
 
extern void nrnmpi_int_gatherv(int* s, int scnt, int* r, int* rcnt, int* rdispl, int root) {
    MPI_Gatherv(s, scnt, MPI_INT, r, rcnt, rdispl, MPI_INT, root, nrnmpi_comm);
}
 
extern void nrnmpi_char_gatherv(char* s, int scnt, char* r, int* rcnt, int* rdispl, int root) {
    MPI_Gatherv(s, scnt, MPI_CHAR, r, rcnt, rdispl, MPI_CHAR, root, nrnmpi_comm);
}
 
extern void nrnmpi_int_scatter(int* s, int* r, int cnt, int root) {
    MPI_Scatter(s, cnt, MPI_INT, r, cnt, MPI_INT, root, nrnmpi_comm);
}
 
extern void nrnmpi_char_scatterv(char* s, int* scnt, int* sdispl, char* r, int rcnt, int root) {
    MPI_Scatterv(s, scnt, sdispl, MPI_CHAR, r, rcnt, MPI_CHAR, root, nrnmpi_comm);
}
 
extern void nrnmpi_int_alltoall(int* s, int* r, int n) {
    MPI_Alltoall(s, n, MPI_INT, r, n, MPI_INT, nrnmpi_comm);
}
 
extern void nrnmpi_int_alltoallv(int* s, int* scnt, int* sdispl, int* r, int* rcnt, int* rdispl) {
    MPI_Alltoallv(s, scnt, sdispl, MPI_INT, r, rcnt, rdispl, MPI_INT, nrnmpi_comm);
}
 
extern void nrnmpi_long_alltoallv(int64_t* s,
                                  int* scnt,
                                  int* sdispl,
                                  int64_t* r,
                                  int* rcnt,
                                  int* rdispl) {
    MPI_Alltoallv(s, scnt, sdispl, MPI_INT64_T, r, rcnt, rdispl, MPI_INT64_T, nrnmpi_comm);
}
 
extern void nrnmpi_dbl_alltoallv(double* s,
                                 int* scnt,
                                 int* sdispl,
                                 double* r,
                                 int* rcnt,
                                 int* rdispl) {
    MPI_Alltoallv(s, scnt, sdispl, MPI_DOUBLE, r, rcnt, rdispl, MPI_DOUBLE, nrnmpi_comm);
}
 
extern void nrnmpi_char_alltoallv(char* s,
                                  int* scnt,
                                  int* sdispl,
                                  char* r,
                                  int* rcnt,
                                  int* rdispl) {
    MPI_Alltoallv(s, scnt, sdispl, MPI_CHAR, r, rcnt, rdispl, MPI_CHAR, nrnmpi_comm);
}
 
/* following are for the partrans */
 
void nrnmpi_int_allgather(int* s, int* r, int n) {
    MPI_Allgather(s, n, MPI_INT, r, n, MPI_INT, nrnmpi_comm);
}
 
void nrnmpi_int_allgather_inplace(int* srcdest, int n) {
    MPI_Allgather(MPI_IN_PLACE, 0, MPI_DATATYPE_NULL, srcdest, n, MPI_INT, nrnmpi_comm);
}
 
void nrnmpi_int_allgatherv(int* s, int* r, int* n, int* dspl) {
    MPI_Allgatherv(s, n[nrnmpi_myid], MPI_INT, r, n, dspl, MPI_INT, nrnmpi_comm);
}
 
void nrnmpi_int_allgatherv_inplace(int* srcdest, int* n, int* dspl) {
    MPI_Allgatherv(MPI_IN_PLACE, 0, MPI_DATATYPE_NULL, srcdest, n, dspl, MPI_INT, nrnmpi_comm);
}
 
void nrnmpi_char_allgatherv(char* s, char* r, int* n, int* dspl) {
    MPI_Allgatherv(s, n[nrnmpi_myid], MPI_CHAR, r, n, dspl, MPI_CHAR, nrnmpi_comm);
}
 
void nrnmpi_long_allgatherv(int64_t* s, int64_t* r, int* n, int* dspl) {
    MPI_Allgatherv(s, n[nrnmpi_myid], MPI_INT64_T, r, n, dspl, MPI_INT64_T, nrnmpi_comm);
}
 
void nrnmpi_long_allgatherv_inplace(long* srcdest, int* n, int* dspl) {
    MPI_Allgatherv(MPI_IN_PLACE, 0, MPI_DATATYPE_NULL, srcdest, n, dspl, MPI_LONG, nrnmpi_comm);
}
 
void nrnmpi_dbl_allgatherv(double* s, double* r, int* n, int* dspl) {
    MPI_Allgatherv(s, n[nrnmpi_myid], MPI_DOUBLE, r, n, dspl, MPI_DOUBLE, nrnmpi_comm);
}
 
void nrnmpi_dbl_allgatherv_inplace(double* srcdest, int* n, int* dspl) {
    MPI_Allgatherv(MPI_IN_PLACE, 0, MPI_DATATYPE_NULL, srcdest, n, dspl, MPI_DOUBLE, nrnmpi_comm);
}
 
void nrnmpi_dbl_broadcast(double* buf, int cnt, int root) {
    MPI_Bcast(buf, cnt, MPI_DOUBLE, root, nrnmpi_comm);
}
 
void nrnmpi_int_broadcast(int* buf, int cnt, int root) {
    MPI_Bcast(buf, cnt, MPI_INT, root, nrnmpi_comm);
}
 
void nrnmpi_char_broadcast(char* buf, int cnt, int root) {
    MPI_Bcast(buf, cnt, MPI_CHAR, root, nrnmpi_comm);
}
 
void nrnmpi_char_broadcast_world(char** pstr, int root) {
    int sz;
    sz = *pstr ? (strlen(*pstr) + 1) : 0;
    MPI_Bcast(&sz, 1, MPI_INT, root, nrnmpi_world_comm);
    if (nrnmpi_myid_world != root) {
        if (*pstr) {
            free(*pstr);
            *pstr = NULL;
        }
        if (sz) {
            *pstr = static_cast<char*>(hoc_Emalloc(sz * sizeof(char)));
            hoc_malchk();
        }
    }
    if (sz) {
        MPI_Bcast(*pstr, sz, MPI_CHAR, root, nrnmpi_world_comm);
    }
}
 
int nrnmpi_int_sum_reduce(int in) {
    int result;
    MPI_Allreduce(&in, &result, 1, MPI_INT, MPI_SUM, nrnmpi_comm);
    return result;
}
 
void nrnmpi_assert_opstep(int opstep, double t) {
    /* all machines in comm should have same opstep and same t. */
    double buf[2];
    if (nrnmpi_numprocs < 2) {
        return;
    }
    buf[0] = (double) opstep;
    buf[1] = t;
    MPI_Bcast(buf, 2, MPI_DOUBLE, 0, nrnmpi_comm);
    if (opstep != (int) buf[0] || t != buf[1]) {
        printf(
            "%d opstep=%d %d  t=%g t-troot=%g\n", nrnmpi_myid, opstep, (int) buf[0], t, t - buf[1]);
        hoc_execerror("nrnmpi_assert_opstep failed", (char*) 0);
    }
}
 
double nrnmpi_dbl_allmin(double x) {
    double result;
    if (nrnmpi_numprocs < 2) {
        return x;
    }
    MPI_Allreduce(&x, &result, 1, MPI_DOUBLE, MPI_MIN, nrnmpi_comm);
    return result;
}
 
static void pgvts_op(double* in, double* inout, int* len, MPI_Datatype* dptr) {
    int i, r = 0;
    assert(*dptr == MPI_DOUBLE);
    assert(*len == 4);
    if (in[0] < inout[0]) {
        /* least time has highest priority */
        r = 1;
    } else if (in[0] == inout[0]) {
        /* when times are equal then */
        if (in[1] < inout[1]) {
            /* NetParEvent done last */
            r = 1;
        } else if (in[1] == inout[1]) {
            /* when times and ops are equal then */
            if (in[2] < inout[2]) {
                /* init done next to last.*/
                r = 1;
            } else if (in[2] == inout[2]) {
                /* when times, ops, and inits are equal then */
                if (in[3] < inout[3]) {
                    /* choose lowest rank */
                    r = 1;
                }
            }
        }
    }
    if (r) {
        for (i = 0; i < 4; ++i) {
            inout[i] = in[i];
        }
    }
}
 
int nrnmpi_pgvts_least(double* t, int* op, int* init) {
    int i;
    double ibuf[4], obuf[4];
    ibuf[0] = *t;
    ibuf[1] = (double) (*op);
    ibuf[2] = (double) (*init);
    ibuf[3] = (double) nrnmpi_myid;
    for (i = 0; i < 4; ++i) {
        obuf[i] = ibuf[i];
    }
    MPI_Allreduce(ibuf, obuf, 4, MPI_DOUBLE, mpi_pgvts_op, nrnmpi_comm);
    assert(obuf[0] <= *t);
    if (obuf[0] == *t) {
        assert((int) obuf[1] <= *op);
        if ((int) obuf[1] == *op) {
            assert((int) obuf[2] <= *init);
            if ((int) obuf[2] == *init) {
                assert((int) obuf[3] <= nrnmpi_myid);
            }
        }
    }
    *t = obuf[0];
    *op = (int) obuf[1];
    *init = (int) obuf[2];
    if (nrnmpi_myid == (int) obuf[3]) {
        return 1;
    }
    return 0;
}
 
/* following for splitcell.cpp transfer */
void nrnmpi_send_doubles(double* pd, int cnt, int dest, int tag) {
    MPI_Send(pd, cnt, MPI_DOUBLE, dest, tag, nrnmpi_comm);
}
 
void nrnmpi_recv_doubles(double* pd, int cnt, int src, int tag) {
    MPI_Status status;
    MPI_Recv(pd, cnt, MPI_DOUBLE, src, tag, nrnmpi_comm, &status);
}
 
void nrnmpi_postrecv_doubles(double* pd, int cnt, int src, int tag, void** request) {
    MPI_Irecv(pd, cnt, MPI_DOUBLE, src, tag, nrnmpi_comm, (MPI_Request*) request);
}
 
void nrnmpi_wait(void** request) {
    MPI_Status status;
    MPI_Wait((MPI_Request*) request, &status);
}
 
void nrnmpi_barrier() {
    if (nrnmpi_numprocs < 2) {
        return;
    }
    MPI_Barrier(nrnmpi_comm);
}
 
double nrnmpi_dbl_allreduce(double x, int type) {
    double result;
    MPI_Op t;
    if (nrnmpi_numprocs < 2) {
        return x;
    }
    if (type == 1) {
        t = MPI_SUM;
    } else if (type == 2) {
        t = MPI_MAX;
    } else {
        t = MPI_MIN;
    }
    MPI_Allreduce(&x, &result, 1, MPI_DOUBLE, t, nrnmpi_comm);
    return result;
}
 
extern "C" void nrnmpi_dbl_allreduce_vec(double* src, double* dest, int cnt, int type) {
    int i;
    MPI_Op t;
    assert(src != dest);
    if (nrnmpi_numprocs < 2) {
        for (i = 0; i < cnt; ++i) {
            dest[i] = src[i];
        }
        return;
    }
    if (type == 1) {
        t = MPI_SUM;
    } else if (type == 2) {
        t = MPI_MAX;
    } else {
        t = MPI_MIN;
    }
    MPI_Allreduce(src, dest, cnt, MPI_DOUBLE, t, nrnmpi_comm);
    return;
}
 
void nrnmpi_longdbl_allreduce_vec(longdbl* src, longdbl* dest, int cnt, int type) {
    int i;
    MPI_Op t;
    assert(src != dest);
    if (nrnmpi_numprocs < 2) {
        for (i = 0; i < cnt; ++i) {
            dest[i] = src[i];
        }
        return;
    }
    if (type == 1) {
        t = MPI_SUM;
    } else if (type == 2) {
        t = MPI_MAX;
    } else {
        t = MPI_MIN;
    }
    MPI_Allreduce(src, dest, cnt, MPI_LONG_DOUBLE, t, nrnmpi_comm);
    return;
}
 
void nrnmpi_long_allreduce_vec(long* src, long* dest, int cnt, int type) {
    int i;
    MPI_Op t;
    assert(src != dest);
    if (nrnmpi_numprocs < 2) {
        for (i = 0; i < cnt; ++i) {
            dest[i] = src[i];
        }
        return;
    }
    if (type == 1) {
        t = MPI_SUM;
    } else if (type == 2) {
        t = MPI_MAX;
    } else {
        t = MPI_MIN;
    }
    MPI_Allreduce(src, dest, cnt, MPI_LONG, t, nrnmpi_comm);
    return;
}
 
void nrnmpi_dbl_allgather(double* s, double* r, int n) {
    MPI_Allgather(s, n, MPI_DOUBLE, r, n, MPI_DOUBLE, nrnmpi_comm);
}
 
#if BGPDMA
 
static MPI_Comm bgp_comm;
 
void nrnmpi_bgp_comm() {
    if (!bgp_comm) {
        MPI_Comm_dup(nrnmpi_comm, &bgp_comm);
    }
}
 
void nrnmpi_bgp_multisend(NRNMPI_Spike* spk, int n, int* hosts) {
    int i;
    MPI_Request r;
    MPI_Status status;
    for (i = 0; i < n; ++i) {
        MPI_Isend(spk, 1, spike_type, hosts[i], 1, bgp_comm, &r);
        MPI_Request_free(&r);
    }
}
 
int nrnmpi_bgp_single_advance(NRNMPI_Spike* spk) {
    int flag = 0;
    MPI_Status status;
    MPI_Iprobe(MPI_ANY_SOURCE, 1, bgp_comm, &flag, &status);
    if (flag) {
        MPI_Recv(spk, 1, spike_type, MPI_ANY_SOURCE, 1, bgp_comm, &status);
    }
    return flag;
}
 
static int iii;
int nrnmpi_bgp_conserve(int nsend, int nrecv) {
    int tcnts[2];
    tcnts[0] = nsend - nrecv;
    MPI_Allreduce(tcnts, tcnts + 1, 1, MPI_INT, MPI_SUM, bgp_comm);
    return tcnts[1];
}
 
#endif /*BGPDMA*/
 
#endif /*NRNMPI*/