/* -*- Mode: C; c-basic-offset:4 ; indent-tabs-mode:nil ; -*- */
/*
 *
 *  (C) 2001 by Argonne National Laboratory.
 *      See COPYRIGHT in top-level directory.
 */

#include "mpiimpl.h"

/* -- Begin Profiling Symbol Block for routine MPI_Cart_sub */
#if defined(HAVE_PRAGMA_WEAK)
#pragma weak MPI_Cart_sub = PMPI_Cart_sub
#elif defined(HAVE_PRAGMA_HP_SEC_DEF)
#pragma _HP_SECONDARY_DEF PMPI_Cart_sub  MPI_Cart_sub
#elif defined(HAVE_PRAGMA_CRI_DUP)
#pragma _CRI duplicate MPI_Cart_sub as PMPI_Cart_sub
#elif defined(HAVE_WEAK_ATTRIBUTE)
int MPI_Cart_sub(MPI_Comm comm, const int remain_dims[], MPI_Comm * newcomm)
    __attribute__ ((weak, alias("PMPI_Cart_sub")));
#endif
/* -- End Profiling Symbol Block */

/* Define MPICH_MPI_FROM_PMPI if weak symbols are not supported to build
   the MPI routines */
#ifndef MPICH_MPI_FROM_PMPI
#undef MPI_Cart_sub
#define MPI_Cart_sub PMPI_Cart_sub

#endif

#undef FUNCNAME
#define FUNCNAME MPI_Cart_sub
#undef FCNAME
#define FCNAME MPL_QUOTE(FUNCNAME)
/*@

MPI_Cart_sub - Partitions a communicator into subgroups which
               form lower-dimensional cartesian subgrids

Input Parameters:
+ comm - communicator with cartesian structure (handle)
- remain_dims - the  'i'th entry of remain_dims specifies whether the 'i'th
dimension is kept in the subgrid (true) or is dropped (false) (logical
vector)

Output Parameters:
. newcomm - communicator containing the subgrid that includes the calling
process (handle)

.N ThreadSafe

.N Fortran

.N Errors
.N MPI_SUCCESS
.N MPI_ERR_TOPOLOGY
.N MPI_ERR_COMM
.N MPI_ERR_ARG
@*/
int MPI_Cart_sub(MPI_Comm comm, const int remain_dims[], MPI_Comm * newcomm)
{
    int mpi_errno = MPI_SUCCESS, all_false;
    int ndims, key, color, ndims_in_subcomm, nnodes_in_subcomm, i, j, rank;
    MPIR_Comm *comm_ptr = NULL, *newcomm_ptr;
    MPIR_Topology *topo_ptr, *toponew_ptr;
    MPIR_CHKPMEM_DECL(4);
    MPIR_FUNC_TERSE_STATE_DECL(MPID_STATE_MPI_CART_SUB);

    MPIR_ERRTEST_INITIALIZED_ORDIE();

    MPID_THREAD_CS_ENTER(GLOBAL, MPIR_THREAD_GLOBAL_ALLFUNC_MUTEX);
    MPIR_FUNC_TERSE_ENTER(MPID_STATE_MPI_CART_SUB);

    /* Validate parameters, especially handles needing to be converted */
#ifdef HAVE_ERROR_CHECKING
    {
        MPID_BEGIN_ERROR_CHECKS;
        {
            MPIR_ERRTEST_COMM(comm, mpi_errno);
        }
        MPID_END_ERROR_CHECKS;
    }
#endif

    /* Convert MPI object handles to object pointers */
    MPIR_Comm_get_ptr(comm, comm_ptr);

    /* Validate parameters and objects (post conversion) */
#ifdef HAVE_ERROR_CHECKING
    {
        MPID_BEGIN_ERROR_CHECKS;
        {
            /* Validate comm_ptr */
            MPIR_Comm_valid_ptr(comm_ptr, mpi_errno, FALSE);
            /* If comm_ptr is not valid, it will be reset to null */
            if (mpi_errno)
                goto fn_fail;
        }
        MPID_END_ERROR_CHECKS;
    }
#endif /* HAVE_ERROR_CHECKING */

    /* ... body of routine ...  */

    /* Check that the communicator already has a Cartesian topology */
    topo_ptr = MPIR_Topology_get(comm_ptr);

    MPIR_ERR_CHKANDJUMP(!topo_ptr, mpi_errno, MPI_ERR_TOPOLOGY, "**notopology");
    MPIR_ERR_CHKANDJUMP(topo_ptr->kind != MPI_CART, mpi_errno, MPI_ERR_TOPOLOGY, "**notcarttopo");

    ndims = topo_ptr->topo.cart.ndims;

    all_false = 1;      /* all entries in remain_dims are false */
    for (i = 0; i < ndims; i++) {
        if (remain_dims[i]) {
            /* any 1 is true, set flag to 0 and break */
            all_false = 0;
            break;
        }
    }

    if (all_false) {
        /* ndims=0, or all entries in remain_dims are false.
         * MPI 2.1 says return a 0D Cartesian topology. */
        mpi_errno = MPIR_Cart_create_impl(comm_ptr, 0, NULL, NULL, 0, newcomm);
        if (mpi_errno)
            MPIR_ERR_POP(mpi_errno);
    } else {
        /* Determine the number of remaining dimensions */
        ndims_in_subcomm = 0;
        nnodes_in_subcomm = 1;
        for (i = 0; i < ndims; i++) {
            if (remain_dims[i]) {
                ndims_in_subcomm++;
                nnodes_in_subcomm *= topo_ptr->topo.cart.dims[i];
            }
        }

        /* Split this communicator.  Do this even if there are no remaining
         * dimensions so that the topology information is attached */
        key = 0;
        color = 0;
        for (i = 0; i < ndims; i++) {
            if (remain_dims[i]) {
                key = (key * topo_ptr->topo.cart.dims[i]) + topo_ptr->topo.cart.position[i];
            } else {
                color = (color * topo_ptr->topo.cart.dims[i]) + topo_ptr->topo.cart.position[i];
            }
        }
        mpi_errno = MPIR_Comm_split_impl(comm_ptr, color, key, &newcomm_ptr);
        if (mpi_errno)
            MPIR_ERR_POP(mpi_errno);

        *newcomm = newcomm_ptr->handle;

        /* Save the topology of this new communicator */
        MPIR_CHKPMEM_MALLOC(toponew_ptr, MPIR_Topology *, sizeof(MPIR_Topology),
                            mpi_errno, "toponew_ptr", MPL_MEM_COMM);

        toponew_ptr->kind = MPI_CART;
        toponew_ptr->topo.cart.ndims = ndims_in_subcomm;
        toponew_ptr->topo.cart.nnodes = nnodes_in_subcomm;
        if (ndims_in_subcomm) {
            MPIR_CHKPMEM_MALLOC(toponew_ptr->topo.cart.dims, int *,
                                ndims_in_subcomm * sizeof(int), mpi_errno, "cart.dims",
                                MPL_MEM_COMM);
            MPIR_CHKPMEM_MALLOC(toponew_ptr->topo.cart.periodic, int *,
                                ndims_in_subcomm * sizeof(int), mpi_errno, "cart.periodic",
                                MPL_MEM_COMM);
            MPIR_CHKPMEM_MALLOC(toponew_ptr->topo.cart.position, int *,
                                ndims_in_subcomm * sizeof(int), mpi_errno, "cart.position",
                                MPL_MEM_COMM);
        } else {
            toponew_ptr->topo.cart.dims = 0;
            toponew_ptr->topo.cart.periodic = 0;
            toponew_ptr->topo.cart.position = 0;
        }

        j = 0;
        for (i = 0; i < ndims; i++) {
            if (remain_dims[i]) {
                toponew_ptr->topo.cart.dims[j] = topo_ptr->topo.cart.dims[i];
                toponew_ptr->topo.cart.periodic[j] = topo_ptr->topo.cart.periodic[i];
                j++;
            }
        }

        /* Compute the position of this process in the new communicator */
        rank = newcomm_ptr->rank;
        for (i = 0; i < ndims_in_subcomm; i++) {
            nnodes_in_subcomm /= toponew_ptr->topo.cart.dims[i];
            toponew_ptr->topo.cart.position[i] = rank / nnodes_in_subcomm;
            rank = rank % nnodes_in_subcomm;
        }

        mpi_errno = MPIR_Topology_put(newcomm_ptr, toponew_ptr);
        if (mpi_errno)
            goto fn_fail;
    }
    /* ... end of body of routine ... */

  fn_exit:
    MPIR_FUNC_TERSE_EXIT(MPID_STATE_MPI_CART_SUB);
    MPID_THREAD_CS_EXIT(GLOBAL, MPIR_THREAD_GLOBAL_ALLFUNC_MUTEX);
    return mpi_errno;

  fn_fail:
    /* --BEGIN ERROR HANDLING-- */
    MPIR_CHKPMEM_REAP();
#ifdef HAVE_ERROR_CHECKING
    {
        mpi_errno =
            MPIR_Err_create_code(mpi_errno, MPIR_ERR_RECOVERABLE, FCNAME, __LINE__, MPI_ERR_OTHER,
                                 "**mpi_cart_sub", "**mpi_cart_sub %C %p %p", comm, remain_dims,
                                 newcomm);
    }
#endif
    mpi_errno = MPIR_Err_return_comm(comm_ptr, FCNAME, mpi_errno);
    goto fn_exit;
    /* --END ERROR HANDLING-- */
}
