Tpetra_Details_iallreduce.hpp

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#ifndef TPETRA_DETAILS_IALLREDUCE_HPP
#define TPETRA_DETAILS_IALLREDUCE_HPP


#include "TpetraCore_config.h"
#include "Teuchos_EReductionType.hpp"
#ifdef HAVE_TPETRACORE_MPI
#  include "Tpetra_Details_extractMpiCommFromTeuchos.hpp"
#  include "Tpetra_Details_MpiTypeTraits.hpp"
#endif // HAVE_TPETRACORE_MPI
#include "Kokkos_Core.hpp"
#include <memory>
#include <stdexcept>
#include <type_traits>
#include <functional>

#ifndef DOXYGEN_SHOULD_SKIP_THIS
namespace Teuchos {
  // forward declaration of Comm
  template<class OrdinalType> class Comm;
} // namespace Teuchos
#endif // NOT DOXYGEN_SHOULD_SKIP_THIS

namespace Tpetra {
namespace Details {

class CommRequest {
public:
  virtual ~CommRequest () {}

  virtual void wait () = 0;

  virtual void cancel () = 0;
};

// Don't rely on anything in this namespace.  You shouldn't be relying
// on anything in Tpetra::Details anyway.  You _especially_ shouldn't
// be relying on anything in Tpetra::Details::Impl.  Consider
// yourselves warned!
namespace Impl {

std::shared_ptr<CommRequest>
emptyCommRequest ();

#ifdef HAVE_TPETRACORE_MPI

class MpiCommRequest : public CommRequest {
public:
  MpiCommRequest ();

  MpiCommRequest (const MPI_Request req);

  virtual ~MpiCommRequest ();

  virtual void wait ();

  virtual void waitWithStatus (MPI_Status& status);

  virtual void cancel ();

private:
  MPI_Request req_;
};
#endif // HAVE_TPETRACORE_MPI

class DeferredActionCommRequest : public CommRequest {
public:
  DeferredActionCommRequest ();

  DeferredActionCommRequest (std::function<void () > action);

  void wait ();

  void cancel ();

private:
  std::function<void(void) > action_;
  bool actionTaken_;
};

template<class PacketType,
         class SendLayoutType,
         class SendDeviceType,
         class RecvLayoutType,
         class RecvDeviceType,
         const int rank>
class IallreduceCommRequest;

template<class PacketType,
         class SendLayoutType,
         class SendDeviceType,
         class RecvLayoutType,
         class RecvDeviceType>
class IallreduceCommRequest<PacketType,
                            SendLayoutType,
                            SendDeviceType,
                            RecvLayoutType,
                            RecvDeviceType,
                            1> :
    public CommRequest {
public:
  IallreduceCommRequest ()
  {}

  typedef ::Kokkos::View<const PacketType*, SendLayoutType,
                         SendDeviceType> send_buffer_type;
  typedef ::Kokkos::View<PacketType*, RecvLayoutType,
                         RecvDeviceType> recv_buffer_type;

  IallreduceCommRequest (const std::shared_ptr<CommRequest>& req,
                         const send_buffer_type& sendbuf,
                         const recv_buffer_type& recvbuf) :
    req_ (req),
    sendbuf_ (sendbuf),
    recvbuf_ (recvbuf)
  {
    static_assert (std::is_same<SendLayoutType, ::Kokkos::LayoutLeft>::value ||
                   std::is_same<SendLayoutType, ::Kokkos::LayoutRight>::value,
                   "SendLayoutType must be either Kokkos::LayoutLeft or "
                   "Kokkos::LayoutRight.");
    static_assert (std::is_same<RecvLayoutType, ::Kokkos::LayoutLeft>::value ||
                   std::is_same<RecvLayoutType, ::Kokkos::LayoutRight>::value,
                   "RecvLayoutType must be either Kokkos::LayoutLeft or "
                   "Kokkos::LayoutRight.");
  }

  virtual ~IallreduceCommRequest () {
    if (req_.get () != NULL) {
      // We're in a destructor, so don't throw.  We'll just try our best
      // to handle whatever happens here without throwing.
      try {
        req_->cancel ();
      }
      catch (...) {}

      try {
        req_ = std::shared_ptr<CommRequest> ();
      }
      catch (...) {}
    }
  }

  void
  wait ()
  {
    if (req_.get () != NULL) {
      req_->wait ();
      // Relinquish request handle.
      req_ = std::shared_ptr<CommRequest> ();
    }
    // Relinquish references to saved buffers, if we have not already
    // done so.  This operation is idempotent.
    sendbuf_ = send_buffer_type ();
    recvbuf_ = recv_buffer_type ();
  }

  void
  cancel ()
  {
    if (req_.get () != NULL) {
      req_->cancel ();
      // Relinquish request handle.
      req_ = std::shared_ptr<CommRequest> ();
    }
    // Relinquish references to saved buffers, if we have not already
    // done so.  This operation is idempotent.
    sendbuf_ = send_buffer_type ();
    recvbuf_ = recv_buffer_type ();
  }

private:
  std::shared_ptr<CommRequest> req_;

  send_buffer_type sendbuf_;

  recv_buffer_type recvbuf_;
};

template<class PacketType,
         class SendLayoutType,
         class SendDeviceType,
         class RecvLayoutType,
         class RecvDeviceType>
class IallreduceCommRequest<PacketType,
                            SendLayoutType,
                            SendDeviceType,
                            RecvLayoutType,
                            RecvDeviceType,
                            0> :
    public CommRequest {
public:
  IallreduceCommRequest ()
  {}

  typedef ::Kokkos::View<const PacketType, SendLayoutType,
                         SendDeviceType> send_buffer_type;
  typedef ::Kokkos::View<PacketType, RecvLayoutType,
                         RecvDeviceType> recv_buffer_type;

  IallreduceCommRequest (const std::shared_ptr<CommRequest>& req,
                         const send_buffer_type& sendbuf,
                         const recv_buffer_type& recvbuf) :
    req_ (req),
    sendbuf_ (sendbuf),
    recvbuf_ (recvbuf)
  {
    static_assert (std::is_same<SendLayoutType, ::Kokkos::LayoutLeft>::value ||
                   std::is_same<SendLayoutType, ::Kokkos::LayoutRight>::value,
                   "SendLayoutType must be either Kokkos::LayoutLeft or "
                   "Kokkos::LayoutRight.");
    static_assert (std::is_same<RecvLayoutType, ::Kokkos::LayoutLeft>::value ||
                   std::is_same<RecvLayoutType, ::Kokkos::LayoutRight>::value,
                   "RecvLayoutType must be either Kokkos::LayoutLeft or "
                   "Kokkos::LayoutRight.");
  }

  virtual ~IallreduceCommRequest () {
    if (req_.get () != NULL) {
      // We're in a destructor, so don't throw.  We'll just try our best
      // to handle whatever happens here without throwing.
      try {
        req_->cancel ();
      }
      catch (...) {}

      try {
        req_ = std::shared_ptr<CommRequest> ();
      }
      catch (...) {}
    }
  }

  void
  wait ()
  {
    if (req_.get () != NULL) {
      req_->wait ();
      // Relinquish request handle.
      req_ = std::shared_ptr<CommRequest> ();
    }
    // Relinquish references to saved buffers, if we have not already
    // done so.  This operation is idempotent.
    sendbuf_ = send_buffer_type ();
    recvbuf_ = recv_buffer_type ();
  }

  void
  cancel ()
  {
    if (req_.get () != NULL) {
      req_->cancel ();
      // Relinquish request handle.
      req_ = std::shared_ptr<CommRequest> ();
    }
    // Relinquish references to saved buffers, if we have not already
    // done so.  This operation is idempotent.
    sendbuf_ = send_buffer_type ();
    recvbuf_ = recv_buffer_type ();
  }

private:
  std::shared_ptr<CommRequest> req_;

  send_buffer_type sendbuf_;

  recv_buffer_type recvbuf_;
};

template<class PacketType,
         class SendLayoutType,
         class SendDeviceType,
         class RecvLayoutType,
         class RecvDeviceType>
std::shared_ptr<CommRequest>
wrapIallreduceCommRequest (const std::shared_ptr<CommRequest>& req,
                           const ::Kokkos::View<const PacketType*,
                             SendLayoutType,
                             SendDeviceType>& sendbuf,
                           const ::Kokkos::View<PacketType*,
                             RecvLayoutType,
                             RecvDeviceType>& recvbuf)
{
  static_assert (std::is_same<SendLayoutType, ::Kokkos::LayoutLeft>::value ||
                 std::is_same<SendLayoutType, ::Kokkos::LayoutRight>::value,
                 "SendLayoutType must be either Kokkos::LayoutLeft or "
                 "Kokkos::LayoutRight.");
  static_assert (std::is_same<RecvLayoutType, ::Kokkos::LayoutLeft>::value ||
                 std::is_same<RecvLayoutType, ::Kokkos::LayoutRight>::value,
                 "RecvLayoutType must be either Kokkos::LayoutLeft or "
                 "Kokkos::LayoutRight.");
  typedef IallreduceCommRequest<PacketType, SendLayoutType, SendDeviceType,
    RecvLayoutType, RecvDeviceType, 1> req_type;
  return std::shared_ptr<CommRequest> (new req_type (req, sendbuf, recvbuf));
}

template<class PacketType,
         class SendLayoutType,
         class SendDeviceType,
         class RecvLayoutType,
         class RecvDeviceType>
std::shared_ptr<CommRequest>
wrapIallreduceCommRequest (const std::shared_ptr<CommRequest>& req,
                           const ::Kokkos::View<const PacketType,
                             SendLayoutType,
                             SendDeviceType>& sendbuf,
                           const ::Kokkos::View<PacketType,
                             RecvLayoutType,
                             RecvDeviceType>& recvbuf)
{
  static_assert (std::is_same<SendLayoutType, ::Kokkos::LayoutLeft>::value ||
                 std::is_same<SendLayoutType, ::Kokkos::LayoutRight>::value,
                 "SendLayoutType must be either Kokkos::LayoutLeft or "
                 "Kokkos::LayoutRight.");
  static_assert (std::is_same<RecvLayoutType, ::Kokkos::LayoutLeft>::value ||
                 std::is_same<RecvLayoutType, ::Kokkos::LayoutRight>::value,
                 "RecvLayoutType must be either Kokkos::LayoutLeft or "
                 "Kokkos::LayoutRight.");
  typedef IallreduceCommRequest<PacketType, SendLayoutType, SendDeviceType,
    RecvLayoutType, RecvDeviceType, 0> req_type;
  return std::shared_ptr<CommRequest> (new req_type (req, sendbuf, recvbuf));
}

#ifdef HAVE_TPETRACORE_MPI

std::shared_ptr<CommRequest>
iallreduceRawVoid (const void* sendbuf,
                   void* recvbuf,
                   const int count,
                   MPI_Datatype mpiDatatype,
                   const bool mpiDatatypeNeedsFree,
                   const Teuchos::EReductionType op,
                   MPI_Comm comm);

#endif // HAVE_TPETRACORE_MPI

template<class Packet>
std::shared_ptr<CommRequest>
iallreduceRaw (const Packet sendbuf[],
               Packet recvbuf[],
               const int count,
               const ::Teuchos::EReductionType op,
               const ::Teuchos::Comm<int>& comm)
{
#ifdef HAVE_TPETRACORE_MPI
  using ::Tpetra::Details::MpiTypeTraits;

  // mfh 12 Nov 2016: It's reasonable to assume that if users call
  // this function with count > 1, then users should expect that all
  // sent and received data have the same MPI_Datatype.  If count is
  // zero, then it doesn't matter what datatype we use, as long as
  // it's not MPI_DATATYPE_NULL.  For the latter, see e.g., the
  // discussion here:
  //
  // http://lists.mpi-forum.org/pipermail/mpi-forum/2016-January/003159.html

  // FIXME (mfh 14 Nov 2016) For derived MPI_Datatype, it may make
  // sense for us to cache them somewhere for later reuse, rather than
  // constructing and freeing a new one each time.

  MPI_Datatype mpiDatatype = (count > 0) ?
    MpiTypeTraits<Packet>::getType (sendbuf[0]) :
    MPI_BYTE;
  MPI_Comm rawComm = ::Tpetra::Details::extractMpiCommFromTeuchos (comm);
  return iallreduceRawVoid (sendbuf, recvbuf, count, mpiDatatype,
                            MpiTypeTraits<Packet>::needsFree, op, rawComm);
#else // NOT HAVE_TPETRACORE_MPI
  throw std::logic_error ("Tpetra::Details::Impl::iallreduceRaw: This function "
                          "should never be called if MPI is not enabled.  "
                          "Please report this bug to the Tpetra developers.");
#endif // HAVE_TPETRACORE_MPI
}

template<class PacketType,
         class SendLayoutType,
         class SendDeviceType,
         class RecvLayoutType,
         class RecvDeviceType,
         const int rank>
struct Iallreduce {};

template<class PacketType,
         class SendLayoutType,
         class SendDeviceType,
         class RecvLayoutType,
         class RecvDeviceType>
struct Iallreduce<PacketType,
                  SendLayoutType,
                  SendDeviceType,
                  RecvLayoutType,
                  RecvDeviceType,
                  1> {
  typedef ::Kokkos::View<const PacketType*,
                         SendLayoutType,
                         SendDeviceType> send_buffer_type;
  typedef ::Kokkos::View<PacketType*,
                         RecvLayoutType,
                         RecvDeviceType> recv_buffer_type;

  static std::shared_ptr<CommRequest>
  iallreduce (const send_buffer_type& sendbuf,
              const recv_buffer_type& recvbuf,
              const ::Teuchos::EReductionType op,
              const ::Teuchos::Comm<int>& comm)
  {
    static_assert (! std::is_const<PacketType>::value,
                   "PacketType must be a nonconst type.");
    static_assert (std::is_same<SendLayoutType, ::Kokkos::LayoutLeft>::value ||
                   std::is_same<SendLayoutType, ::Kokkos::LayoutRight>::value,
                   "SendLayoutType must be either Kokkos::LayoutLeft or "
                   "Kokkos::LayoutRight.");
    static_assert (std::is_same<RecvLayoutType, ::Kokkos::LayoutLeft>::value ||
                   std::is_same<RecvLayoutType, ::Kokkos::LayoutRight>::value,
                   "RecvLayoutType must be either Kokkos::LayoutLeft or "
                   "Kokkos::LayoutRight.");
#ifdef HAVE_TPETRACORE_MPI
    // Avoid instantiating Impl::iallreduceRaw for both T and const T,
    // by canonicalizing to the non-const version of T.
    typedef typename std::remove_const<PacketType>::type packet_type;

    std::shared_ptr<CommRequest> req =
      Impl::iallreduceRaw<packet_type> (sendbuf.ptr_on_device (),
                                        recvbuf.ptr_on_device (),
                                        static_cast<int> (sendbuf.dimension_0 ()),
                                        op, comm);
    return Impl::wrapIallreduceCommRequest (req, sendbuf, recvbuf);
#else // NOT HAVE_TPETRACORE_MPI

    // MPI is disabled, so comm is a SerialComm.
    // Avoid needing to check the SerialComm case in Impl::iallreduce.
    // That lets Impl::iallreduce not need to know about DeviceType.
    ::Kokkos::deep_copy (recvbuf, sendbuf);
    // This request has already finished.  There's nothing more to do.
    return Impl::emptyCommRequest ();
#endif // HAVE_TPETRACORE_MPI
  }
};

template<class PacketType,
         class SendLayoutType,
         class SendDeviceType,
         class RecvLayoutType,
         class RecvDeviceType>
struct Iallreduce<PacketType,
                  SendLayoutType,
                  SendDeviceType,
                  RecvLayoutType,
                  RecvDeviceType,
                  0> {
  // mfh 02 Jan 2017: For rank-0 Views, LayoutLeft and LayoutRight are
  // unfortunately NOT mutually assignable, even though it would make
  // sense for this to be the case.  That's why we have to template on
  // the layout types.
  typedef ::Kokkos::View<const PacketType,
                         SendLayoutType,
                         SendDeviceType> send_buffer_type;
  typedef ::Kokkos::View<PacketType,
                         RecvLayoutType,
                         RecvDeviceType> recv_buffer_type;

  static std::shared_ptr<CommRequest>
  iallreduce (const send_buffer_type& sendbuf,
              const recv_buffer_type& recvbuf,
              const ::Teuchos::EReductionType op,
              const ::Teuchos::Comm<int>& comm)
  {
    static_assert (! std::is_const<PacketType>::value,
                   "PacketType must be a nonconst type.");
    static_assert (std::is_same<SendLayoutType, ::Kokkos::LayoutLeft>::value ||
                   std::is_same<SendLayoutType, ::Kokkos::LayoutRight>::value,
                   "SendLayoutType must be either Kokkos::LayoutLeft or "
                   "Kokkos::LayoutRight.");
    static_assert (std::is_same<RecvLayoutType, ::Kokkos::LayoutLeft>::value ||
                   std::is_same<RecvLayoutType, ::Kokkos::LayoutRight>::value,
                   "RecvLayoutType must be either Kokkos::LayoutLeft or "
                   "Kokkos::LayoutRight.");
#ifdef HAVE_TPETRACORE_MPI
    // Avoid instantiating Impl::iallreduceRaw for both T and const T,
    // by canonicalizing to the non-const version of T.
    typedef typename std::remove_const<PacketType>::type packet_type;

    std::shared_ptr<CommRequest> req =
      Impl::iallreduceRaw<packet_type> (sendbuf.ptr_on_device (),
                                        recvbuf.ptr_on_device (),
                                        static_cast<int> (1),
                                        op, comm);
    return Impl::wrapIallreduceCommRequest (req, sendbuf, recvbuf);
#else // NOT HAVE_TPETRACORE_MPI

    // MPI is disabled, so comm is a SerialComm.
    // Avoid needing to check the SerialComm case in Impl::iallreduce.
    // That lets Impl::iallreduce not need to know about DeviceType.
    ::Kokkos::deep_copy (recvbuf, sendbuf);
    // This request has already finished.  There's nothing more to do.
    return Impl::emptyCommRequest ();
#endif // HAVE_TPETRACORE_MPI
  }
};

} // namespace Impl

//
// SKIP DOWN TO HERE
//

template<class InputViewType, class OutputViewType>
std::shared_ptr<CommRequest>
iallreduce (const InputViewType& sendbuf,
            const OutputViewType& recvbuf,
            const ::Teuchos::EReductionType op,
            const ::Teuchos::Comm<int>& comm)
{
  static_assert (Kokkos::Impl::is_view<InputViewType>::value,
                 "InputViewType must be a Kokkos::View specialization.");
  static_assert (Kokkos::Impl::is_view<OutputViewType>::value,
                 "OutputViewType must be a Kokkos::View specialization.");
  constexpr int rank = static_cast<int> (OutputViewType::rank);
  static_assert (static_cast<int> (InputViewType::rank) == rank,
                 "InputViewType and OutputViewType must have the same rank.");
  static_assert (rank == 0 || rank == 1,
                 "InputViewType and OutputViewType must both have "
                 "rank 0 or rank 1.");
  typedef typename OutputViewType::non_const_value_type packet_type;
  static_assert (std::is_same<typename OutputViewType::value_type,
                   packet_type>::value,
                 "OutputViewType must be a nonconst Kokkos::View.");
  static_assert (std::is_same<typename InputViewType::non_const_value_type,
                   packet_type>::value,
                 "InputViewType and OutputViewType must be Views "
                 "whose entries have the same type.");
  typedef typename InputViewType::array_layout send_layout_type;
  typedef typename OutputViewType::array_layout recv_layout_type;
  typedef typename InputViewType::device_type send_device_type;
  typedef typename OutputViewType::device_type recv_device_type;

  typedef Impl::Iallreduce<packet_type, send_layout_type, send_device_type,
    recv_layout_type, recv_device_type, rank> impl_type;
  return impl_type::iallreduce (sendbuf, recvbuf, op, comm);
}

} // namespace Details
} // namespace Tpetra

#endif // TPETRA_DETAILS_IALLREDUCE_HPP