Cleanups in legacyheader/types/commrec.h

[gromacs.git] / src / gromacs / domdec / ga2la.h

/*
 * This file is part of the GROMACS molecular simulation package.
 *
 * Copyright (c) 1991-2000, University of Groningen, The Netherlands.
 * Copyright (c) 2001-2004, The GROMACS development team.
 * Copyright (c) 2010,2014,2015, by the GROMACS development team, led by
 * Mark Abraham, David van der Spoel, Berk Hess, and Erik Lindahl,
 * and including many others, as listed in the AUTHORS file in the
 * top-level source directory and at http://www.gromacs.org.
 *
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 * modify it under the terms of the GNU Lesser General Public License
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/*! \libinternal \file
 * \brief
 * Defines structures and functions for mapping from global to local atom
 * indices. The functions are performance critical and should be inlined.
 *
 * \inlibraryapi
 * \ingroup module_domdec
 *
 * \author Berk Hess <hess@kth.se>
 *
 */
#ifndef GMX_DOMDEC_GA2LA_H
#define GMX_DOMDEC_GA2LA_H

#include "gromacs/legacyheaders/types/commrec.h"
#include "gromacs/utility/basedefinitions.h"
#include "gromacs/utility/smalloc.h"

/*! \libinternal \brief Structure for the local atom info for a plain list */
typedef struct {
    int  la;   /**< The local atom index */
    int  cell; /**< The DD zone index for neighboring domains, zone+zone otherwise */
} gmx_laa_t;

/*! \libinternal \brief Structure for the local atom info for a hash table */
typedef struct {
    int  ga;   /**< The global atom index */
    int  la;   /**< The local atom index */
    int  cell; /**< The DD zone index for neighboring domains, zone+zone otherwise */
    int  next; /**< Index in the list of the next element with the same hash, -1 if none */
} gmx_lal_t;

/*! \libinternal \brief Structure for all global to local mapping information */
struct gmx_ga2la_t {
    gmx_bool   bDirectList;        /**< Use a direct list */
    int        mod;                /**< The hash size */
    int        nalloc;             /**< The alloction size of laa or la1 */
    gmx_laa_t *laa;                /**< The direct list */
    gmx_lal_t *lal;                /**< The hash table list */
    int        start_space_search; /**< Index in lal at which to start looking for empty space */
};

/*! \brief Clear all the entries in the ga2la list
 *
 * \param[in,out] ga2la The global to local atom struct
 */
static void ga2la_clear(gmx_ga2la_t *ga2la)
{
    int i;

    if (ga2la->bDirectList)
    {
        for (i = 0; i < ga2la->nalloc; i++)
        {
            ga2la->laa[i].cell = -1;
        }
    }
    else
    {
        for (i = 0; i < ga2la->nalloc; i++)
        {
            ga2la->lal[i].ga   = -1;
            ga2la->lal[i].next = -1;
        }
        ga2la->start_space_search = ga2la->mod;
    }
}

/*! \brief Initializes and returns a pointer to a gmx_ga2la_t structure
 *
 * \param[in] natoms_total  The total number of atoms in the system
 * \param[in] natoms_local  An estimate of the number of home+communicated atoms
 * \return a pointer to an initialized gmx_ga2la_t struct
 */
static gmx_ga2la_t *ga2la_init(int natoms_total, int natoms_local)
{
    gmx_ga2la_t *ga2la;

    snew(ga2la, 1);

    /* There are two methods implemented for finding the local atom number
     * belonging to a global atom number:
     * 1) a simple, direct array
     * 2) a hash table consisting of list of linked lists indexed with
     *    the global number modulo mod.
     * Memory requirements:
     * 1) nat_tot*2 ints
     * 2) nat_loc*(2+1-2(1-e^-1/2))*4 ints
     * where nat_loc is the number of atoms in the home + communicated zones.
     * Method 1 is faster for low parallelization, 2 for high parallelization.
     * We switch to method 2 when it uses less than half the memory method 1.
     */
    ga2la->bDirectList = (natoms_total <= 1024 ||
                          natoms_total <= natoms_local*9);

    if (ga2la->bDirectList)
    {
        ga2la->nalloc = natoms_total;
        snew(ga2la->laa, ga2la->nalloc);
    }
    else
    {
        /* Make the direct list twice as long as the number of local atoms.
         * The fraction of entries in the list with:
         * 0   size lists: e^-1/f
         * >=1 size lists: 1 - e^-1/f
         * where f is: the direct list length / #local atoms
         * The fraction of atoms not in the direct list is: 1-f(1-e^-1/f).
         */
        ga2la->mod    = 2*natoms_local;
        ga2la->nalloc = over_alloc_dd(ga2la->mod);
        snew(ga2la->lal, ga2la->nalloc);
    }

    ga2la_clear(ga2la);

    return ga2la;
}

/*! \brief Sets the ga2la entry for global atom a_gl
 *
 * \param[in,out] ga2la The global to local atom struct
 * \param[in]     a_gl  The global atom index
 * \param[in]     a_loc The local atom index
 * \param[in]     cell  The cell index
 */
static void ga2la_set(gmx_ga2la_t *ga2la, int a_gl, int a_loc, int cell)
{
    int ind, ind_prev, i;

    if (ga2la->bDirectList)
    {
        ga2la->laa[a_gl].la   = a_loc;
        ga2la->laa[a_gl].cell = cell;

        return;
    }

    ind = a_gl % ga2la->mod;

    if (ga2la->lal[ind].ga >= 0)
    {
        /* Search the last entry in the linked list for this index */
        ind_prev = ind;
        while (ga2la->lal[ind_prev].next >= 0)
        {
            ind_prev = ga2la->lal[ind_prev].next;
        }
        /* Search for space in the array */
        ind = ga2la->start_space_search;
        while (ind < ga2la->nalloc && ga2la->lal[ind].ga >= 0)
        {
            ind++;
        }
        /* If we are at the end of the list we need to increase the size */
        if (ind == ga2la->nalloc)
        {
            ga2la->nalloc = over_alloc_dd(ind+1);
            srenew(ga2la->lal, ga2la->nalloc);
            for (i = ind; i < ga2la->nalloc; i++)
            {
                ga2la->lal[i].ga   = -1;
                ga2la->lal[i].next = -1;
            }
        }
        ga2la->lal[ind_prev].next = ind;

        ga2la->start_space_search = ind + 1;
    }
    ga2la->lal[ind].ga   = a_gl;
    ga2la->lal[ind].la   = a_loc;
    ga2la->lal[ind].cell = cell;
}

/*! \brief Delete the ga2la entry for global atom a_gl
 *
 * \param[in,out] ga2la The global to local atom struct
 * \param[in]     a_gl  The global atom index
 */
static void ga2la_del(gmx_ga2la_t *ga2la, int a_gl)
{
    int ind, ind_prev;

    if (ga2la->bDirectList)
    {
        ga2la->laa[a_gl].cell = -1;

        return;
    }

    ind_prev = -1;
    ind      = a_gl % ga2la->mod;
    do
    {
        if (ga2la->lal[ind].ga == a_gl)
        {
            if (ind_prev >= 0)
            {
                ga2la->lal[ind_prev].next = ga2la->lal[ind].next;

                /* This index is a linked entry, so we free an entry.
                 * Check if we are creating the first empty space.
                 */
                if (ind < ga2la->start_space_search)
                {
                    ga2la->start_space_search = ind;
                }
            }
            ga2la->lal[ind].ga   = -1;
            ga2la->lal[ind].cell = -1;
            ga2la->lal[ind].next = -1;

            return;
        }
        ind_prev = ind;
        ind      = ga2la->lal[ind].next;
    }
    while (ind >= 0);

    return;
}

/*! \brief Change the local atom for present ga2la entry for global atom a_gl
 *
 * \param[in,out] ga2la The global to local atom struct
 * \param[in]     a_gl  The global atom index
 * \param[in]     a_loc The new local atom index
 */
static void ga2la_change_la(gmx_ga2la_t *ga2la, int a_gl, int a_loc)
{
    int ind;

    if (ga2la->bDirectList)
    {
        ga2la->laa[a_gl].la = a_loc;

        return;
    }

    ind = a_gl % ga2la->mod;
    do
    {
        if (ga2la->lal[ind].ga == a_gl)
        {
            ga2la->lal[ind].la = a_loc;

            return;
        }
        ind = ga2la->lal[ind].next;
    }
    while (ind >= 0);

    return;
}

/*! \brief Returns if the global atom a_gl available locally
 *
 * \param[in]  ga2la The global to local atom struct
 * \param[in]  a_gl  The global atom index
 * \param[out] a_loc If the return value is TRUE, the local atom index
 * \param[out] cell  If the return value is TRUE, the zone or for atoms more than one cell away zone+nzone
 * \return if the global atom a_gl available locally
 */
static gmx_bool ga2la_get(const gmx_ga2la_t *ga2la, int a_gl, int *a_loc, int *cell)
{
    int ind;

    if (ga2la->bDirectList)
    {
        *a_loc = ga2la->laa[a_gl].la;
        *cell  = ga2la->laa[a_gl].cell;

        return (ga2la->laa[a_gl].cell >= 0);
    }

    ind = a_gl % ga2la->mod;
    do
    {
        if (ga2la->lal[ind].ga == a_gl)
        {
            *a_loc = ga2la->lal[ind].la;
            *cell  = ga2la->lal[ind].cell;

            return TRUE;
        }
        ind = ga2la->lal[ind].next;
    }
    while (ind >= 0);

    return FALSE;
}

/*! \brief Returns if the global atom a_gl is a home atom
 *
 * \param[in]  ga2la The global to local atom struct
 * \param[in]  a_gl  The global atom index
 * \param[out] a_loc If the return value is TRUE, the local atom index
 * \return if the global atom a_gl is a home atom
 */
static gmx_bool ga2la_get_home(const gmx_ga2la_t *ga2la, int a_gl, int *a_loc)
{
    int ind;

    if (ga2la->bDirectList)
    {
        *a_loc = ga2la->laa[a_gl].la;

        return (ga2la->laa[a_gl].cell == 0);
    }

    ind = a_gl % ga2la->mod;
    do
    {
        if (ga2la->lal[ind].ga == a_gl)
        {
            if (ga2la->lal[ind].cell == 0)
            {
                *a_loc = ga2la->lal[ind].la;

                return TRUE;
            }
            else
            {
                return FALSE;
            }
        }
        ind = ga2la->lal[ind].next;
    }
    while (ind >= 0);

    return FALSE;
}

/*! \brief Returns if the global atom a_gl is a home atom
 *
 * \param[in]  ga2la The global to local atom struct
 * \param[in]  a_gl  The global atom index
 * \return if the global atom a_gl is a home atom
 */
static gmx_bool ga2la_is_home(const gmx_ga2la_t *ga2la, int a_gl)
{
    int ind;

    if (ga2la->bDirectList)
    {
        return (ga2la->laa[a_gl].cell == 0);
    }

    ind = a_gl % ga2la->mod;
    do
    {
        if (ga2la->lal[ind].ga == a_gl)
        {
            return (ga2la->lal[ind].cell == 0);
        }
        ind = ga2la->lal[ind].next;
    }
    while (ind >= 0);

    return FALSE;
}

#endif