Move GPU task assignment

[gromacs.git] / src / gromacs / taskassignment / taskassignment.h

/*
 * This file is part of the GROMACS molecular simulation package.
 *
 * Copyright (c) 2017,2018,2019, 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.
 *
 * GROMACS is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public License
 * as published by the Free Software Foundation; either version 2.1
 * of the License, or (at your option) any later version.
 *
 * GROMACS is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with GROMACS; if not, see
 * http://www.gnu.org/licenses, or write to the Free Software Foundation,
 * Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA.
 *
 * If you want to redistribute modifications to GROMACS, please
 * consider that scientific software is very special. Version
 * control is crucial - bugs must be traceable. We will be happy to
 * consider code for inclusion in the official distribution, but
 * derived work must not be called official GROMACS. Details are found
 * in the README & COPYING files - if they are missing, get the
 * official version at http://www.gromacs.org.
 *
 * To help us fund GROMACS development, we humbly ask that you cite
 * the research papers on the package. Check out http://www.gromacs.org.
 */
/*! \defgroup module_taskassignment Assigning simulation tasks to hardware (taskassignment)
 * \ingroup group_mdrun
 * \brief Provides code that manages assignment of simulation tasks to hardware.
 */
/*! \libinternal
 * \file
 * \brief Declares high-level functionality for managing assigning
 * tasks on ranks of a node to hardware on that node, and the factory
 * function to build the correct flavours of gmx::INodeTaskAssigner
 * required to implement the user's requirements.
 *
 * \author Mark Abraham <mark.j.abraham@gmail.com>
 * \ingroup module_taskassignment
 * \inlibraryapi
 */
#ifndef GMX_TASKASSIGNMENT_TASKASSIGNMENT_H
#define GMX_TASKASSIGNMENT_TASKASSIGNMENT_H

#include <vector>

#include "gromacs/utility/basedefinitions.h"

struct gmx_device_info_t;
struct gmx_hw_info_t;
struct gmx_multisim_t;
struct t_commrec;

enum class PmeRunMode;

namespace gmx
{

enum class TaskTarget;
class MDLogger;
class PhysicalNodeCommunicator;

/*! \brief Types of compute tasks that can be run on a GPU.
 *
 * These names refer to existing practice in GROMACS, which is not
 * strictly accurate. */
enum class GpuTask : int
{
    //! Short-ranged interactions.
    Nonbonded,
    //! Long-ranged interactions.
    Pme
};

/*! \libinternal
 * \brief Specifies the GPU deviceID_ available for task_ to use. */
struct GpuTaskMapping
{
    //! The type of this GPU task.
    GpuTask task_;
    //! Device ID on this node to which this GPU task is mapped.
    int     deviceId_;
};

//! Container of GPU tasks on a rank, specifying the task type and GPU device ID, e.g. potentially ready for consumption by the modules on that rank.
using GpuTaskAssignment = std::vector <GpuTaskMapping>;

class GpuTaskAssignments;

/*! \libinternal
 * \brief Builder for the GpuTaskAssignments for all ranks on this
 * node.
 *
 * This will coordinate the final stages of task assignment and
 * reporting, and build the GpuTaskAssignments object used to
 * configure the modules that might run tasks on GPUs.
 *
 * Communicates between ranks on a node to coordinate task assignment
 * between them onto available hardware, e.g. accelerators.
 *
 * \todo Later, this might become a loop over all registered modules
 * relevant to the mdp inputs, to find those that have such tasks.
 *
 * \todo Later we might need the concept of computeTasksOnThisRank,
 * from which we construct gpuTasksOnThisRank.
 *
 * Currently the DD code assigns duty to ranks that can
 * include PP work that currently can be executed on a single
 * GPU, if present and compatible.  This has to be coordinated
 * across PP ranks on a node, with possible multiple devices
 * or sharing devices on a node, either from the user
 * selection, or automatically. */
class GpuTaskAssignmentsBuilder
{
    public:
        //! Constructor
        GpuTaskAssignmentsBuilder();

        /*! \brief Builds a GpuTaskAssignments
         *
         * This method reconciles
         *
         *   - user mdrun command-line options,
         *   - the results of hardware detection
         *   - the duty assigned by the DD setup,
         *   - the requested simulation modules, and
         *   - the possible existence of multi-simulations
         *
         * to assign the GPUs on each physical node to the tasks on
         * the ranks of that node. It throws InconsistentInputError
         * when a/the useful GPU task assignment is not possible.
         *
         * \param[in]  gpuIdsToUse            The compatible GPUs that the user permitted us to use.
         * \param[in]  userGpuTaskAssignment  The user-specified assignment of GPU tasks to device IDs.
         * \param[in]  hardwareInfo           The detected hardware
         * \param[in]  cr                     Communication object.
         * \param[in]  ms                     Multi-simulation handler.
         * \param[in]  physicalNodeComm       Communication object for this physical node.
         * \param[in]  nonbondedTarget        The user's choice for mdrun -nb for where to assign
         *                                    short-ranged nonbonded interaction tasks.
         * \param[in]  pmeTarget              The user's choice for mdrun -pme for where to assign
         *                                    long-ranged PME nonbonded interaction tasks.
         * \param[in]  bondedTarget           The user's choice for mdrun -bonded for where to assign tasks.
         * \param[in]  updateTarget           The user's choice for mdrun -update for where to assign tasks.
         * \param[in]  useGpuForNonbonded     Whether GPUs will be used for nonbonded interactions.
         * \param[in]  useGpuForPme           Whether GPUs will be used for PME interactions.
         * \param[in]  rankHasPpTask          Whether this rank has a PP task
         * \param[in]  rankHasPmeTask         Whether this rank has a PME task
         *
         * \throws   std::bad_alloc          If out of memory.
         *           InconsistentInputError  If user and/or detected inputs are inconsistent.
         */
        GpuTaskAssignments build(const std::vector<int>         &gpuIdsToUse,
                                 const std::vector<int>         &userGpuTaskAssignment,
                                 const gmx_hw_info_t            &hardwareInfo,
                                 const t_commrec                *cr,
                                 const gmx_multisim_t           *ms,
                                 const PhysicalNodeCommunicator &physicalNodeComm,
                                 TaskTarget                      nonbondedTarget,
                                 TaskTarget                      pmeTarget,
                                 TaskTarget                      bondedTarget,
                                 TaskTarget                      updateTarget,
                                 bool                            useGpuForNonbonded,
                                 bool                            useGpuForPme,
                                 bool                            rankHasPpTask,
                                 bool                            rankHasPmeTask);
};

/*! \libinternal
 * \brief Contains the GPU task assignment for all ranks on this
 * physical node.
 *
 * This can be used to configure the modules that might run tasks on
 * GPUs.
 *
 * This assignment is made by a GpuTaskAssignmentsBuilder object. */
class GpuTaskAssignments
{
    public:
        //! Public move constructor to use with the builder
        GpuTaskAssignments(GpuTaskAssignments &&source) noexcept = default;
    private:
        // Let the builder handle construction
        friend class GpuTaskAssignmentsBuilder;
        //! Private constructor so only the builder can construct
        GpuTaskAssignments(const gmx_hw_info_t &hardwareInfo);
        /*! \brief Information about hardware on this physical node
         *
         * The lifetime of the object referred to must exceed that
         * of this object. */
        const gmx_hw_info_t           &hardwareInfo_;
        //! The GPU task assignment for all ranks on this node
        std::vector<GpuTaskAssignment> assignmentForAllRanksOnThisNode_;
        /*! \brief The index of this rank within those on this node.
         *
         * This is useful for indexing into \c
         * assignmentForAllRanksOnThisNode_. */
        index  indexOfThisRank_ = -1;
        //! Number of GPU tasks on this node.
        size_t numGpuTasksOnThisNode_ = 0;
        //! Number of ranks on this physical node.
        size_t numRanksOnThisNode_ = 0;
    public:
        /*! \brief Log a report on how GPUs are being used on
         * the ranks of the physical node of rank 0 of the simulation.
         *
         * \todo It could be useful to report also whether any nodes differed,
         * and in what way.
         *
         * \param[in]  mdlog           Logging object.
         * \param[in]  printHostName   Print the hostname in the usage information
         * \param[in]  useGpuForBonded Whether GPU PP tasks will do bonded work on the GPU
         * \param[in]  pmeRunMode      Describes the execution of PME tasks
         *
         * \throws     std::bad_alloc if out of memory */
        void
        reportGpuUsage(const MDLogger &mdlog,
                       bool            printHostName,
                       bool            useGpuForBonded,
                       PmeRunMode      pmeRunMode);
        /*! \brief Logs to \c mdlog information that may help a user
         * learn how to let mdrun make a task assignment that runs
         * faster.
         *
         * \param[in]  mdlog                        Logging object.
         * \param[in]  numCompatibleGpusOnThisNode  The number of compatible GPUs on this node.
         * */
        void logPerformanceHints(const MDLogger &mdlog,
                                 size_t          numCompatibleGpusOnThisNode);
        /*! \brief Return handle to the initialized GPU to use for the
         * nonbonded task on this rank, if any.
         *
         * Returns nullptr if no such task is assigned to this rank.
         *
         * \todo This also sets up DLB for device sharing, where
         * appropriate, but that responsbility should move
         * elsewhere. */
        gmx_device_info_t *initNonbondedDevice(const t_commrec *cr) const;
        /*! \brief Return handle to the initialized GPU to use for the
         * PME task on this rank, if any.
         *
         * Returns nullptr if no such task is assigned to this rank. */
        gmx_device_info_t *initPmeDevice() const;
        //! Return whether this rank has a PME task running on a GPU
        bool thisRankHasPmeGpuTask() const;
        //! Return whether this rank has any task running on a GPU
        bool thisRankHasAnyGpuTask() const;
};

//! Function for whether the task of \c mapping has value \c TaskType.
template<GpuTask TaskType>
bool hasTaskType(const GpuTaskMapping &mapping)
{
    return mapping.task_ == TaskType;
}

}  // namespace gmx

#endif