operations.h

// Copyright 2018 Uber Technologies, Inc. All Rights Reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
// =============================================================================

#ifndef HOROVOD_OPERATIONS_H
#define HOROVOD_OPERATIONS_H

#include <functional>

#include "common.h"

namespace horovod {
namespace common {

// Device ID used for CPU.
#define CPU_DEVICE_ID -1

// A callback to call after the MPI communication completes. Since the
// allreduce and allgather ops are asynchronous, this callback is what resumes
// computation after the reduction is completed.
typedef std::function<void(const Status&)> StatusCallback;

// Check that Horovod is initialized.
Status CheckInitialized();

extern "C" {

// C interface to initialize Horovod.
void horovod_init();

// C interface to get index of current Horovod process.
// Returns -1 if Horovod is not initialized.
int horovod_rank();

// C interface to get index of current Horovod process in the node it is on.
// Returns -1 if Horovod is not initialized.
int horovod_local_rank();

// C interface to return number of Horovod processes.
// Returns -1 if Horovod is not initialized.
int horovod_size();

// C interface to return number of Horovod processes in the node it is on.
// Returns -1 if Horovod is not initialized.
int horovod_local_size();

// C interface to return flag indicating whether MPI multi-threading is
// supported. Returns -1 if Horovod is not initialized.
int horovod_mpi_threads_supported();
}

void EnqueueTensorAllreduce(std::shared_ptr<OpContext> context,
                            std::shared_ptr<Tensor> tensor,
                            std::shared_ptr<Tensor> output,
                            std::shared_ptr<ReadyEvent> ready_event,
                            const std::string name, const int device,
                            StatusCallback callback);

void EnqueueTensorAllgather(std::shared_ptr<OpContext> context,
                            std::shared_ptr<Tensor> tensor,
                            std::shared_ptr<ReadyEvent> ready_event,
                            const std::string name, const int device,
                            StatusCallback callback);

void EnqueueTensorBroadcast(std::shared_ptr<OpContext> context,
                            std::shared_ptr<Tensor> tensor,
                            std::shared_ptr<Tensor> output, int root_rank,
                            std::shared_ptr<ReadyEvent> ready_event,
                            const std::string name, const int device,
                            StatusCallback callback);

} // namespace common
} // namespace horovod

#endif // HOROVOD_OPERATIONS_H