Caffe2 doesn't seem to see cuDNN?
I am trying to install SpConv (spatially sparse convolution library), however when running python3 setup.py bdist_wheel, I get an error which seems to be related to Caffe2 not being able to see cuDNN, as I infer from this message: 

CMake Error at /home/ivan/.local/lib/python3.6/site-packages/torch/share/cmake/Caffe2/Caffe2Config.cmake:96 (message):
  Your installed Caffe2 version uses cuDNN but I cannot find the cuDNN
  libraries.  Please set the proper cuDNN prefixes and / or install cuDNN.


I have tried reinstalling cuDNN but no luck. Can I manually point Caffe2 to cuDNN? This is because usually cuda is located in /usr/local/cuda/, however I have it in /usr/lib/cuda.

Full output below:

running bdist_wheel
running build
running build_py
running build_ext
Release
|||||CMAKE ARGS||||| ['-DCMAKE_PREFIX_PATH=/home/ivan/.local/lib/python3.6/site-packages/torch', '-DPYBIND11_PYTHON_VERSION=3.6', '-DSPCONV_BuildTests=OFF', '-DCMAKE_CUDA_FLAGS="--expt-relaxed-constexpr" -D__CUDA_NO_HALF_OPERATORS__ -D__CUDA_NO_HALF_CONVERSIONS__ -D__CUDA_NO_HALF2_OPERATORS__', '-DCMAKE_LIBRARY_OUTPUT_DIRECTORY=/mnt/home/ivan/second.pytorch/second/spconv/build/lib.linux-x86_64-3.6/spconv', '-DCMAKE_BUILD_TYPE=Release']
-- Caffe2: CUDA detected: 9.1
-- Caffe2: CUDA nvcc is: /usr/bin/nvcc
-- Caffe2: CUDA toolkit directory: /usr
-- Caffe2: Header version is: 9.1
-- Could NOT find CUDNN (missing: CUDNN_INCLUDE_DIR) 
CMake Warning at /home/ivan/.local/lib/python3.6/site-packages/torch/share/cmake/Caffe2/public/cuda.cmake:131 (message):
  Caffe2: Cannot find cuDNN library.  Turning the option off
Call Stack (most recent call first):
  /home/ivan/.local/lib/python3.6/site-packages/torch/share/cmake/Caffe2/Caffe2Config.cmake:88 (include)
  /home/ivan/.local/lib/python3.6/site-packages/torch/share/cmake/Torch/TorchConfig.cmake:40 (find_package)
  CMakeLists.txt:20 (find_package)


-- Autodetected CUDA architecture(s):  6.1
-- Added CUDA NVCC flags for: -gencode;arch=compute_61,code=sm_61
CMake Error at /home/ivan/.local/lib/python3.6/site-packages/torch/share/cmake/Caffe2/Caffe2Config.cmake:96 (message):
  Your installed Caffe2 version uses cuDNN but I cannot find the cuDNN
  libraries.  Please set the proper cuDNN prefixes and / or install cuDNN.
Call Stack (most recent call first):
  /home/ivan/.local/lib/python3.6/site-packages/torch/share/cmake/Torch/TorchConfig.cmake:40 (find_package)
  CMakeLists.txt:20 (find_package)


-- Configuring incomplete, errors occurred!
See also "/mnt/home/ivan/second.pytorch/second/spconv/build/temp.linux-x86_64-3.6/CMakeFiles/CMakeOutput.log".
See also "/mnt/home/ivan/second.pytorch/second/spconv/build/temp.linux-x86_64-3.6/CMakeFiles/CMakeError.log".
Traceback (most recent call last):
  File "setup.py", line 99, in &lt;module&gt;
    zip_safe=False,
  File "/home/ivan/.local/lib/python3.6/site-packages/setuptools/__init__.py", line 145, in setup
    return distutils.core.setup(**attrs)
  File "/usr/lib/python3.6/distutils/core.py", line 148, in setup
    dist.run_commands()
  File "/usr/lib/python3.6/distutils/dist.py", line 955, in run_commands
    self.run_command(cmd)
  File "/usr/lib/python3.6/distutils/dist.py", line 974, in run_command
    cmd_obj.run()
  File "/usr/lib/python3/dist-packages/wheel/bdist_wheel.py", line 204, in run
    self.run_command('build')
  File "/usr/lib/python3.6/distutils/cmd.py", line 313, in run_command
    self.distribution.run_command(command)
  File "/usr/lib/python3.6/distutils/dist.py", line 974, in run_command
    cmd_obj.run()
  File "/usr/lib/python3.6/distutils/command/build.py", line 135, in run
    self.run_command(cmd_name)
  File "/usr/lib/python3.6/distutils/cmd.py", line 313, in run_command
    self.distribution.run_command(command)
  File "/usr/lib/python3.6/distutils/dist.py", line 974, in run_command
    cmd_obj.run()
  File "setup.py", line 40, in run
    self.build_extension(ext)
  File "setup.py", line 82, in build_extension
    subprocess.check_call(['cmake', ext.sourcedir] + cmake_args, cwd=self.build_temp, env=env)
  File "/usr/lib/python3.6/subprocess.py", line 311, in check_call
    raise CalledProcessError(retcode, cmd)
subprocess.CalledProcessError: Command '['cmake', '/mnt/home/ivan/second.pytorch/second/spconv', '-DCMAKE_PREFIX_PATH=/home/ivan/.local/lib/python3.6/site-packages/torch', '-DPYBIND11_PYTHON_VERSION=3.6', '-DSPCONV_BuildTests=OFF', '-DCMAKE_CUDA_FLAGS="--expt-relaxed-constexpr" -D__CUDA_NO_HALF_OPERATORS__ -D__CUDA_NO_HALF_CONVERSIONS__ -D__CUDA_NO_HALF2_OPERATORS__', '-DCMAKE_LIBRARY_OUTPUT_DIRECTORY=/mnt/home/ivan/second.pytorch/second/spconv/build/lib.linux-x86_64-3.6/spconv', '-DCMAKE_BUILD_TYPE=Release']' returned non-zero exit status 1.


System: Ubuntu 18.04, CUDA 9.1, cuDNN 7.6.3

Found the problem. I needed to set CUDNN_INCLUDE_DIR to /usr/lib/cuda/include (i.e. where the cudnn.h file is located).

Lesson learnt: take time to understand the error, missing: CUDNN_INCLUDE_DIR was key. 
