/* Copyright 2017 The TensorFlow Authors. 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.
==============================================================================*/

#include "tensorflow/compiler/xla/service/generic_transfer_manager.h"

#include <string>
#include <utility>
#include <vector>

#include "tensorflow/compiler/xla/literal_util.h"
#include "tensorflow/compiler/xla/shape_util.h"
#include "tensorflow/compiler/xla/status_macros.h"
#include "tensorflow/compiler/xla/statusor.h"
#include "tensorflow/compiler/xla/types.h"
#include "tensorflow/compiler/xla/util.h"
#include "tensorflow/compiler/xla/xla_data.pb.h"
#include "tensorflow/core/lib/core/errors.h"
#include "tensorflow/core/platform/logging.h"
#include "tensorflow/core/platform/stream_executor_no_cuda.h"

namespace se = ::perftools::gputools;

namespace xla {

GenericTransferManager::GenericTransferManager(se::Platform::Id platform_id)
    : platform_id_(platform_id) {
  // We currently only support kHostPlatformId for CPU and kCudaPlatformId for
  // GPU. Before supporting other platforms, we need to test this transfer
  // manager on them.
  CHECK(platform_id_ == se::host::kHostPlatformId ||
        platform_id_ == se::cuda::kCudaPlatformId);
}

se::Platform::Id GenericTransferManager::PlatformId() const {
  if (platform_id_ == se::cuda::kCudaPlatformId ||
      platform_id_ == se::host::kHostPlatformId) {
    return platform_id_;
  }
  CHECK(false) << "GenericTransferManager::platform_id_ is invalid";
}

Status GenericTransferManager::TransferLiteralFromDevice(
    se::StreamExecutor* executor, const se::DeviceMemoryBase& source,
    const Shape& device_shape, const Shape& literal_shape, Literal* literal) {
  VLOG(2) << "transferring literal shape from device: "
          << ShapeUtil::HumanString(literal_shape)
          << "; device location: " << source.opaque();
  TF_RET_CHECK(ShapeUtil::Compatible(device_shape, literal_shape));

  // Tuples are a special case and contain one or more shapes inside of them to
  // an arbitrary nesting depth.
  if (device_shape.element_type() == TUPLE) {
    *literal->mutable_shape() = literal_shape;
    TF_ASSIGN_OR_RETURN(
        std::vector<se::DeviceMemoryBase> element_buffers,
        ShallowCopyTupleFromDevice(executor, source, device_shape));
    TF_RET_CHECK(element_buffers.size() ==
                 ShapeUtil::TupleElementCount(device_shape));
    for (int64 i = 0; i < element_buffers.size(); ++i) {
      const Shape& element_device_shape = device_shape.tuple_shapes(i);
      const Shape& element_literal_shape = literal_shape.tuple_shapes(i);
      Literal* element_literal = literal->add_tuple_literals();
      // Recursively call TransferFromDevice to copy over the data in the
      // element array.
      TF_RETURN_IF_ERROR(TransferLiteralFromDevice(
          executor, element_buffers[i], /*device_shape=*/element_device_shape,
          /*literal_shape=*/element_literal_shape, element_literal));
    }
    return Status::OK();
  }

  *literal->mutable_shape() = device_shape;
  literal->Reserve(ShapeUtil::ElementsIn(device_shape));
  TF_RETURN_IF_ERROR(TransferBufferFromDevice(
      executor, source, /*size=*/ShapeUtil::ByteSizeOf(device_shape),
      /*destination=*/literal->MutableInternalData()));
  if (!ShapeUtil::Equal(literal_shape, device_shape)) {
    literal->Swap(literal->Relayout(literal_shape.layout()).get());
  }
  TF_RET_CHECK(ShapeUtil::Equal(literal_shape, literal->shape()));
  return Status::OK();
}

StatusOr<std::vector<se::DeviceMemoryBase>>
GenericTransferManager::ShallowCopyTupleFromDevice(
    se::StreamExecutor* executor, const se::DeviceMemoryBase& source,
    const Shape& shape) {
  TF_RET_CHECK(ShapeUtil::IsTuple(shape));

  // For devices which use the GenericTransferManager, a tuple is stored as an
  // array of pointers to buffers. Copy the contents of the tuple buffer into
  // a vector of void* pointers.
  std::vector<void*> element_pointers(ShapeUtil::TupleElementCount(shape),
                                      nullptr);
  int64 tuple_size =
      ShapeUtil::ByteSizeOf(shape, /*pointer_size=*/sizeof(void*));
  auto copy_status = executor->SynchronousMemcpyD2H(source, tuple_size,
                                                    element_pointers.data());
  if (!copy_status.ok()) {
    return AddStatus(
        Status(static_cast<tensorflow::error::Code>(copy_status.code()),
               copy_status.error_message()),
        "failed transfer of tuple buffer " + ShapeUtil::HumanString(shape));
  }

  // Create a DeviceMemoryBase from each void* pointer.
  std::vector<se::DeviceMemoryBase> destination;
  for (size_t i = 0; i < element_pointers.size(); ++i) {
    if (element_pointers[i] == nullptr &&
        !ShapeUtil::HasZeroElements(shape.tuple_shapes(i))) {
      return FailedPrecondition("tuple contains nullptr at element %lu", i);
    }
    int64 buffer_size = ShapeUtil::ByteSizeOf(shape.tuple_shapes(i),
                                              /*pointer_size=*/sizeof(void*));
    destination.emplace_back(element_pointers[i], buffer_size);
  }
  return std::move(destination);
}

Status GenericTransferManager::TransferLiteralToDevice(
    se::StreamExecutor* executor, const Literal& literal,
    se::DeviceMemoryBase* destination) {
  const Shape& shape = literal.shape();
  VLOG(2) << "transferring literal shape to device: "
          << ShapeUtil::HumanString(shape)
          << "; device location: " << destination->opaque();

  if (ShapeUtil::IsTuple(literal.shape())) {
    std::vector<void*> tuple_elements_on_device;
    for (const Literal& tuple_element : literal.tuple_literals()) {
      se::DeviceMemoryBase allocation = executor->AllocateArray<uint8>(
          GetByteSizeRequirement(tuple_element.shape()));
      TF_RETURN_IF_ERROR(
          TransferLiteralToDevice(executor, tuple_element, &allocation));
      tuple_elements_on_device.push_back(allocation.opaque());
    }
    return TransferBufferToDevice(
        executor, tuple_elements_on_device.size() * sizeof(void*),
        tuple_elements_on_device.data(), destination);
  }

  return TransferBufferToDevice(executor,
                                /*size=*/GetByteSizeRequirement(shape),
                                /*source=*/literal.InternalData(), destination);
}

Status GenericTransferManager::TransferLiteralToInfeed(
    se::StreamExecutor* executor, const Literal& literal) {
  return Unimplemented("Generic transfer to Infeed");
}

Status GenericTransferManager::TransferBufferToInfeed(
    perftools::gputools::StreamExecutor* executor, int64 size,
    const void* source) {
  return Unimplemented("Generic transfer to Infeed");
}

Status GenericTransferManager::TransferLiteralFromOutfeed(
    perftools::gputools::StreamExecutor* executor, const Shape& literal_shape,
    Literal* literal) {
  return Unimplemented(
      "Outfeed is not supported on this platform (b/30467474)");
}

Status GenericTransferManager::ResetDevices(
    tensorflow::gtl::ArraySlice<perftools::gputools::StreamExecutor*>
    /*executors*/) {
  return Unimplemented(
      "Device reset is not yet supported on this platform (b/30481585)");
}

int64 GenericTransferManager::GetByteSizeRequirement(const Shape& shape) {
  return ShapeUtil::ByteSizeOf(shape, /*pointer_size=*/sizeof(void*));
}

}  // namespace xla
