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/*! \internal \file
 * \brief Defines the domain decomposition helper for the modular simulator
 *
 * \author Pascal Merz <pascal.merz@me.com>
 * \ingroup module_modularsimulator
 */

#include "gmxpre.h"

#include "domdechelper.h"

#include "gromacs/domdec/collect.h"
#include "gromacs/domdec/partition.h"
#include "gromacs/mdtypes/commrec.h"
#include "gromacs/mdtypes/inputrec.h"
#include "gromacs/mdtypes/state.h"
#include "gromacs/pbcutil/pbc.h"

#include "freeenergyperturbationdata.h"
#include "statepropagatordata.h"
#include "topologyholder.h"

namespace gmx
{
DomDecHelper::DomDecHelper(bool                          isVerbose,
                           int                           verbosePrintInterval,
                           StatePropagatorData*          statePropagatorData,
                           TopologyHolder*               topologyHolder,
                           FILE*                         fplog,
                           t_commrec*                    cr,
                           const MDLogger&               mdlog,
                           Constraints*                  constr,
                           const t_inputrec*             inputrec,
                           MDAtoms*                      mdAtoms,
                           t_nrnb*                       nrnb,
                           gmx_wallcycle*                wcycle,
                           t_forcerec*                   fr,
                           VirtualSitesHandler*          vsite,
                           ImdSession*                   imdSession,
                           pull_t*                       pull_work,
                           std::vector<DomDecCallback>&& domdecCallbacks) :
    nextNSStep_(-1),
    isVerbose_(isVerbose),
    verbosePrintInterval_(verbosePrintInterval),
    domdecCallbacks_(std::move(domdecCallbacks)),
    statePropagatorData_(statePropagatorData),
    topologyHolder_(topologyHolder),
    fplog_(fplog),
    cr_(cr),
    mdlog_(mdlog),
    constr_(constr),
    inputrec_(inputrec),
    mdAtoms_(mdAtoms),
    nrnb_(nrnb),
    wcycle_(wcycle),
    fr_(fr),
    vsite_(vsite),
    imdSession_(imdSession),
    pull_work_(pull_work)
{
    GMX_ASSERT(haveDDAtomOrdering(*cr),
               "Domain decomposition Helper constructed in non-DD simulation");
}

void DomDecHelper::setup()
{
    // constant choices for this call to dd_partition_system
    const bool     verbose     = false;
    const bool     isMainState = true;
    gmx_wallcycle* wcycle      = nullptr;

    // Distribute the charge groups over the nodes from the main node
    partitionSystem(verbose,
                    isMainState,
                    wcycle,
                    statePropagatorData_->localState(),
                    statePropagatorData_->globalState());
}

void DomDecHelper::run(Step step, Time gmx_unused time)
{
    if (step != nextNSStep_ || (step == inputrec_->init_step && inputrec_->bContinuation))
    {
        return;
    }
    t_state* localState  = statePropagatorData_->localState();
    t_state* globalState = statePropagatorData_->globalState();

    // constant choices for this call to dd_partition_system
    const bool verbose = isVerbose_ && (step % verbosePrintInterval_ == 0 || step == inputrec_->init_step);
    bool isMainState = false;

    // Correct the new box if it is too skewed
    if (inputrecDynamicBox(inputrec_))
    {
        // TODO: Correcting the box is done here (if using DD) or in ForceElement (non-DD simulations).
        //       Think about unifying this responsibility, could this be done in one place?
        if (correct_box(fplog_, step, localState->box))
        {
            isMainState = true;
        }
    }
    if (isMainState)
    {
        dd_collect_state(cr_->dd, localState, globalState);
    }

    // Distribute the charge groups over the nodes from the main node
    partitionSystem(verbose, isMainState, wcycle_, localState, globalState);
}

void DomDecHelper::partitionSystem(bool           verbose,
                                   bool           isMainState,
                                   gmx_wallcycle* wcycle,
                                   t_state*       localState,
                                   t_state*       globalState)
{
    ForceBuffers* forcePointer = statePropagatorData_->forcePointer();

    // Work-around to keep dd_partition_system from failing -
    // we're not actually using the information related to Nose-Hoover chains
    localState->nhchainlength = inputrec_->opts.nhchainlength;
    // Distribute the charge groups over the nodes from the main node
    dd_partition_system(fplog_,
                        mdlog_,
                        inputrec_->init_step,
                        cr_,
                        isMainState,
                        globalState,
                        topologyHolder_->globalTopology(),
                        *inputrec_,
                        imdSession_,
                        pull_work_,
                        localState,
                        forcePointer,
                        mdAtoms_,
                        topologyHolder_->localTopology_,
                        fr_,
                        vsite_,
                        constr_,
                        nrnb_,
                        wcycle,
                        verbose);
    statePropagatorData_->setLocalState(localState);
    for (const auto& callback : domdecCallbacks_)
    {
        callback();
    }
}

std::optional<SignallerCallback> DomDecHelper::registerNSCallback()
{
    return [this](Step step, Time gmx_unused time) { this->nextNSStep_ = step; };
}

void DomDecHelperBuilder::registerClient(IDomDecHelperClient* client)
{
    if (!client)
    {
        return;
    }
    if (state_ == ModularSimulatorBuilderState::NotAcceptingClientRegistrations)
    {
        GMX_THROW(SimulationAlgorithmSetupError(
                "Tried to register to DomDecHelper after it was built."));
    }
    clients_.emplace_back(client);
}

} // namespace gmx
