src/gromacs/domdec/dlb.h

   1 /*
   2  * This file is part of the GROMACS molecular simulation package.
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   4  * Copyright (c) 2018,2019, by the GROMACS development team, led by
   5  * Mark Abraham, David van der Spoel, Berk Hess, and Erik Lindahl,
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  35 /*! \libinternal \file
  36  *
  37  * \brief This file declares functions to interact with the dynamic load
  38  * balancing machinery.
  39  *
  40  * \author Berk Hess <hess@kth.se>
  41  * \inlibraryapi
  42  * \ingroup module_domdec
  43  */
  44
  45 #ifndef GMX_DOMDEC_DLB_H
  46 #define GMX_DOMDEC_DLB_H
  47
  48 #include "gromacs/utility/real.h"
  49
  50 struct gmx_domdec_t;
  51 struct t_commrec;
  52
  53
  54 /*! \brief We check if to turn on DLB at the first and every 100 DD partitionings.
  55  * With large imbalance DLB will turn on at the first step, so we can
  56  * make the interval so large that the MPI overhead of the check is negligible.
  57  */
  58 constexpr int c_checkTurnDlbOnInterval = 100;
  59 /*! \brief We need to check if DLB results in worse performance and then turn it off.
  60  * We check this more often then for turning DLB on, because the DLB can scale
  61  * the domains very rapidly, so if unlucky the load imbalance can go up quickly
  62  * and furthermore, we are already synchronizing often with DLB, so
  63  * the overhead of the MPI Bcast is not that high.
  64  */
  65 constexpr int c_checkTurnDlbOffInterval = 20;
  66
  67
  68 /*! \brief Return the PME/PP force load ratio, or -1 if nothing was measured.
  69  *
  70  * Should only be called on the DD master node.
  71  */
  72 float dd_pme_f_ratio(const gmx_domdec_t* dd);
  73
  74 //! Sets the cell size limits for DD to suit dynamic load balancing.
  75 void set_dlb_limits(gmx_domdec_t* dd);
  76
  77 /*! \brief Limit DLB to preserve the option of returning to the current cut-off.
  78  *
  79  * Domain boundary changes due to the DD dynamic load balancing can limit
  80  * the cut-off distance that can be set in change_dd_cutoff. This function
  81  * sets/changes the DLB limit such that using the passed (pair-list) cut-off
  82  * should still be possible after subsequently setting a shorter cut-off
  83  * with change_dd_cutoff.
  84  */
  85 void set_dd_dlb_max_cutoff(struct t_commrec* cr, real cutoff);
  86
  87 /*! \brief Sets whether we should later check the load imbalance data, so that
  88  * we can trigger dynamic load balancing if enough imbalance has
  89  * arisen.
  90  *
  91  * Used after PME load balancing unlocks DLB, so that the check
  92  * whether DLB will be useful can happen immediately.
  93  */
  94 void dd_dlb_set_should_check_whether_to_turn_dlb_on(gmx_domdec_t* dd, bool bValue);
  95
  96 /*! \brief Returns if we should check whether there has been enough
  97  * load imbalance to trigger dynamic load balancing.
  98  *
  99  * We need to check whether we check because it might be always off.
 100  */
 101 bool dd_dlb_get_should_check_whether_to_turn_dlb_on(gmx_domdec_t* dd);
 102
 103 /*! \brief Return if we are currently using dynamic load balancing */
 104 bool dd_dlb_is_on(const gmx_domdec_t* dd);
 105
 106 /*! \brief Return if the DLB lock is set */
 107 bool dd_dlb_is_locked(const gmx_domdec_t* dd);
 108
 109 /*! \brief Set a lock such that with DLB=auto DLB cannot get turned on */
 110 void dd_dlb_lock(struct gmx_domdec_t* dd);
 111
 112 /*! \brief Clear a lock such that with DLB=auto DLB may get turned on later */
 113 void dd_dlb_unlock(struct gmx_domdec_t* dd);
 114
 115 #endif