if(NOT WITH_GPU)
  return()
endif()

if(WIN32)
  set(CUDNN_ROOT ${CUDA_TOOLKIT_ROOT_DIR})
else()
  set(CUDNN_ROOT
      "/usr"
      CACHE PATH "CUDNN ROOT")
endif()

find_path(
  CUDNN_INCLUDE_DIR cudnn.h
  PATHS ${CUDNN_ROOT} ${CUDNN_ROOT}/include $ENV{CUDNN_ROOT}
        $ENV{CUDNN_ROOT}/include ${CUDA_TOOLKIT_INCLUDE}
  NO_DEFAULT_PATH)

get_filename_component(__libpath_hist ${CUDA_CUDART_LIBRARY} PATH)

set(TARGET_ARCH "x86_64")
if(NOT ${CMAKE_SYSTEM_PROCESSOR})
  set(TARGET_ARCH ${CMAKE_SYSTEM_PROCESSOR})
endif()

list(
  APPEND
  CUDNN_CHECK_LIBRARY_DIRS
  ${CUDNN_ROOT}
  ${CUDNN_ROOT}/lib64
  ${CUDNN_ROOT}/lib
  ${CUDNN_ROOT}/lib/${TARGET_ARCH}-linux-gnu
  ${CUDNN_ROOT}/local/cuda-${CUDA_VERSION}/targets/${TARGET_ARCH}-linux/lib/
  $ENV{CUDNN_ROOT}
  $ENV{CUDNN_ROOT}/lib64
  $ENV{CUDNN_ROOT}/lib
  /usr/lib
  ${CUDA_TOOLKIT_ROOT_DIR}
  ${CUDA_TOOLKIT_ROOT_DIR}/lib/x64)
set(CUDNN_LIB_NAME "")

if(LINUX)
  set(CUDNN_LIB_NAME "libcudnn.so")
endif()

if(WIN32)
  # only support cudnn7
  set(CUDNN_LIB_NAME "cudnn.lib" "cudnn64_7.dll")
endif()

if(APPLE)
  set(CUDNN_LIB_NAME "libcudnn.dylib" "libcudnn.so")
endif()

find_library(
  CUDNN_LIBRARY
  NAMES ${CUDNN_LIB_NAME} # libcudnn_static.a
  PATHS ${CUDNN_CHECK_LIBRARY_DIRS} ${CUDNN_INCLUDE_DIR} ${__libpath_hist}
  NO_DEFAULT_PATH
  DOC "Path to cuDNN library.")

if(CUDNN_INCLUDE_DIR AND CUDNN_LIBRARY)
  set(CUDNN_FOUND ON)
else()
  set(CUDNN_FOUND OFF)
endif()

macro(find_cudnn_version cudnn_header_file)
  file(READ ${cudnn_header_file} CUDNN_VERSION_FILE_CONTENTS)
  get_filename_component(CUDNN_LIB_PATH ${CUDNN_LIBRARY} DIRECTORY)

  string(REGEX MATCH "define CUDNN_VERSION +([0-9]+)" CUDNN_VERSION
               "${CUDNN_VERSION_FILE_CONTENTS}")
  string(REGEX REPLACE "define CUDNN_VERSION +([0-9]+)" "\\1" CUDNN_VERSION
                       "${CUDNN_VERSION}")

  if("${CUDNN_VERSION}" STREQUAL "2000")
    message(STATUS "Current cuDNN version is v2. ")
  else()
    string(REGEX MATCH "define CUDNN_MAJOR +([0-9]+)" CUDNN_MAJOR_VERSION
                 "${CUDNN_VERSION_FILE_CONTENTS}")
    string(REGEX REPLACE "define CUDNN_MAJOR +([0-9]+)" "\\1"
                         CUDNN_MAJOR_VERSION "${CUDNN_MAJOR_VERSION}")
    string(REGEX MATCH "define CUDNN_MINOR +([0-9]+)" CUDNN_MINOR_VERSION
                 "${CUDNN_VERSION_FILE_CONTENTS}")
    string(REGEX REPLACE "define CUDNN_MINOR +([0-9]+)" "\\1"
                         CUDNN_MINOR_VERSION "${CUDNN_MINOR_VERSION}")
    string(REGEX MATCH "define CUDNN_PATCHLEVEL +([0-9]+)"
                 CUDNN_PATCHLEVEL_VERSION "${CUDNN_VERSION_FILE_CONTENTS}")
    string(REGEX REPLACE "define CUDNN_PATCHLEVEL +([0-9]+)" "\\1"
                         CUDNN_PATCHLEVEL_VERSION "${CUDNN_PATCHLEVEL_VERSION}")

    if(NOT CUDNN_MAJOR_VERSION)
      set(CUDNN_VERSION "???")
    else()
      add_definitions("-DCUDNN_MAJOR_VERSION=\"${CUDNN_MAJOR_VERSION}\"")
      math(EXPR CUDNN_VERSION "${CUDNN_MAJOR_VERSION} * 1000 +
                 ${CUDNN_MINOR_VERSION} * 100 + ${CUDNN_PATCHLEVEL_VERSION}")
      message(
        STATUS
          "Current cuDNN header is ${cudnn_header_file} "
          "Current cuDNN version is v${CUDNN_MAJOR_VERSION}.${CUDNN_MINOR_VERSION}.${CUDNN_PATCHLEVEL_VERSION}. "
      )
    endif()
  endif()
endmacro()

if(CUDNN_FOUND)
  find_cudnn_version(${CUDNN_INCLUDE_DIR}/cudnn.h)
  if(NOT CUDNN_MAJOR_VERSION)
    find_cudnn_version(${CUDNN_INCLUDE_DIR}/cudnn_version.h)
  endif()
endif()