/**
 * Copyright (c) Facebook, Inc. and its affiliates.
 *
 * This source code is licensed under the MIT license found in the
 * LICENSE file in the root directory of this source tree.
 */


#include "DeviceUtils.h"
#include "DeviceDefs.cuh"
#include "../../FaissAssert.h"
#include <mutex>
#include <unordered_map>

namespace faiss { namespace gpu {

int getCurrentDevice() {
  int dev = -1;
  CUDA_VERIFY(cudaGetDevice(&dev));
  FAISS_ASSERT(dev != -1);

  return dev;
}

void setCurrentDevice(int device) {
  CUDA_VERIFY(cudaSetDevice(device));
}

int getNumDevices() {
  int numDev = -1;
  cudaError_t err = cudaGetDeviceCount(&numDev);
  if (cudaErrorNoDevice == err) {
    numDev = 0;
  } else {
    CUDA_VERIFY(err);
  }
  FAISS_ASSERT(numDev != -1);

  return numDev;
}

void synchronizeAllDevices() {
  for (int i = 0; i < getNumDevices(); ++i) {
    DeviceScope scope(i);

    CUDA_VERIFY(cudaDeviceSynchronize());
  }
}

const cudaDeviceProp& getDeviceProperties(int device) {
  static std::mutex mutex;
  static std::unordered_map<int, cudaDeviceProp> properties;

  std::lock_guard<std::mutex> guard(mutex);

  auto it = properties.find(device);
  if (it == properties.end()) {
    cudaDeviceProp prop;
    CUDA_VERIFY(cudaGetDeviceProperties(&prop, device));

    properties[device] = prop;
    it = properties.find(device);
  }

  return it->second;
}

const cudaDeviceProp& getCurrentDeviceProperties() {
  return getDeviceProperties(getCurrentDevice());
}

int getMaxThreads(int device) {
  return getDeviceProperties(device).maxThreadsPerBlock;
}

int getMaxThreadsCurrentDevice() {
  return getMaxThreads(getCurrentDevice());
}

size_t getMaxSharedMemPerBlock(int device) {
  return getDeviceProperties(device).sharedMemPerBlock;
}

size_t getMaxSharedMemPerBlockCurrentDevice() {
  return getMaxSharedMemPerBlock(getCurrentDevice());
}

int getDeviceForAddress(const void* p) {
  if (!p) {
    return -1;
  }

  cudaPointerAttributes att;
  cudaError_t err = cudaPointerGetAttributes(&att, p);
  FAISS_ASSERT(err == cudaSuccess ||
         err == cudaErrorInvalidValue);

  if (err == cudaErrorInvalidValue) {
    // Make sure the current thread error status has been reset
    err = cudaGetLastError();
    FAISS_ASSERT(err == cudaErrorInvalidValue);
    return -1;
  } else if (att.memoryType == cudaMemoryTypeHost) {
    return -1;
  } else {
    return att.device;
  }
}

bool getFullUnifiedMemSupport(int device) {
  const auto& prop = getDeviceProperties(device);
  return (prop.major >= 6);
}

bool getFullUnifiedMemSupportCurrentDevice() {
  return getFullUnifiedMemSupport(getCurrentDevice());
}

int getMaxKSelection() {
  // Don't use the device at the moment, just base this based on the CUDA SDK
  // that we were compiled with
  return GPU_MAX_SELECTION_K;
}

DeviceScope::DeviceScope(int device) {
  prevDevice_ = getCurrentDevice();

  if (prevDevice_ != device) {
    setCurrentDevice(device);
  } else {
    prevDevice_ = -1;
  }
}

DeviceScope::~DeviceScope() {
  if (prevDevice_ != -1) {
    setCurrentDevice(prevDevice_);
  }
}

CublasHandleScope::CublasHandleScope() {
  auto blasStatus = cublasCreate(&blasHandle_);
  FAISS_ASSERT(blasStatus == CUBLAS_STATUS_SUCCESS);
}

CublasHandleScope::~CublasHandleScope() {
  auto blasStatus = cublasDestroy(blasHandle_);
  FAISS_ASSERT(blasStatus == CUBLAS_STATUS_SUCCESS);
}

CudaEvent::CudaEvent(cudaStream_t stream)
    : event_(0) {
  CUDA_VERIFY(cudaEventCreateWithFlags(&event_, cudaEventDisableTiming));
  CUDA_VERIFY(cudaEventRecord(event_, stream));
}

CudaEvent::CudaEvent(CudaEvent&& event) noexcept
    : event_(std::move(event.event_)) {
  event.event_ = 0;
}

CudaEvent::~CudaEvent() {
  if (event_) {
    CUDA_VERIFY(cudaEventDestroy(event_));
  }
}

CudaEvent&
CudaEvent::operator=(CudaEvent&& event) noexcept {
  event_ = std::move(event.event_);
  event.event_ = 0;

  return *this;
}

void
CudaEvent::streamWaitOnEvent(cudaStream_t stream) {
  CUDA_VERIFY(cudaStreamWaitEvent(stream, event_, 0));
}

void
CudaEvent::cpuWaitOnEvent() {
  CUDA_VERIFY(cudaEventSynchronize(event_));
}

} } // namespace
