CuDNN is not available in binary-installed cupy - chainer

Question

I installed Cupy using the binary package cupy-cuda92, but CuDNN is not loaded.
$ pip install cupy-cuda92==5.4.0 chainer==5.4.0
$ python -c 'import chainer; chainer.print_runtime_info()'
/home/xxxxx/.pyenv/versions/3.5.2/lib/python3.5/site-packages/chainer/backends/cuda.py:98: UserWarning: cuDNN is not enabled.
Please reinstall CuPy after you install cudnn
(see https://docs-cupy.chainer.org/en/stable/install.html#install-cudnn).
'cuDNN is not enabled.\n'
Platform: Linux-4.4.0-103-generic-x86_64-with-debian-stretch-sid
Chainer: 5.3.0
NumPy: 1.16.2
CuPy:
CuPy Version : 5.3.0
CUDA Root : /usr/local/cuda
CUDA Build Version : 9020
CUDA Driver Version : 9020
CUDA Runtime Version : 9020
cuDNN Build Version : None
cuDNN Version : None
NCCL Build Version : 2307
NCCL Runtime Version : 2402
iDeep: Not Available
I tried uninstalling & reinstalling chainer and cupy with --no-cache-dir but saw no difference. I also confirmed that CUDA is 9.2.
$ nvcc --version
nvcc: NVIDIA (R) Cuda compiler driver
Copyright (c) 2005-2018 NVIDIA Corporation
Built on Wed_Apr_11_23:16:29_CDT_2018
Cuda compilation tools, release 9.2, V9.2.88

Answer 1

I found the problem and a solution on my own.
First I tried to import cudnn directly.
$ python
Python 3.5.2 (default, Mar 25 2019, 10:54:56)
[GCC 5.4.0 20160609] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import cupy.cuda.cudnn
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
ImportError: /home/xxxxx/.pyenv/versions/3.5.2/lib/python3.5/site-packages/cupy/cuda/cudnn.cpython-35m-x86_64-linux-gnu.so: symbol cudnnGetBatchNormalizationTrainingExReserveSpaceSize, version libcudnn.so.7 not defined in file libcudnn.so.7 with link time reference
thus there is a kind of library version mismatch. I checked my LD_LIBRARY_PATH and found that different versions of CuDNN are installed via cudnnenv. I removed them from LD_LIBRARY_PATH and the problem was gone.
$ python -c 'import chainer; chainer.print_runtime_info()'
Platform: Linux-4.4.0-103-generic-x86_64-with-debian-stretch-sid
Chainer: 5.3.0
NumPy: 1.16.2
CuPy:
CuPy Version : 5.3.0
CUDA Root : /usr/local/cuda
CUDA Build Version : 9020
CUDA Driver Version : 9020
CUDA Runtime Version : 9020
cuDNN Build Version : 7402
cuDNN Version : 7500
NCCL Build Version : 2307
NCCL Runtime Version : 2402
iDeep: Not Available