How to let cmake find CUDA

Question

I am trying to build this project, which has CUDA as a dependency. But the cmake script cannot find the CUDA installation on the system:

cls ~/workspace/gpucluster/cluster/build $ cmake ..
-- The C compiler identification is GNU 4.7.1
-- The CXX compiler identification is GNU 4.7.1
-- Check for working C compiler: /usr/bin/gcc
-- Check for working C compiler: /usr/bin/gcc -- works
-- Detecting C compiler ABI info
-- Detecting C compiler ABI info - done
-- Check for working CXX compiler: /usr/bin/c++
-- Check for working CXX compiler: /usr/bin/c++ -- works
-- Detecting CXX compiler ABI info
-- Detecting CXX compiler ABI info - done
CMake Error at /usr/share/cmake/Modules/FindCUDA.cmake:488 (message):
  Specify CUDA_TOOLKIT_ROOT_DIR
Call Stack (most recent call first):
  CMakeLists.txt:20 (find_package)

-- Configuring incomplete, errors occurred!

I've tried adding it as an environment variable to .bashrc, to no effect:

export CUDA_TOOLKIT_ROOT_DIR=/usr/local/cuda-5.5

How do I Specify CUDA_TOOLKIT_ROOT_DIR correctly?

Answer 1

FindCMake.cmake looks for /usr/local/cuda. In your case, that directory might not be there. Just create a symbolic link of that name to your actual CUDA installation directory:

$ sudo ln -s /usr/local/cuda-5.5 /usr/local/cuda

Your CMake should be able to generate the Makefile for your project now.

Answer 2

Since CMake 3.8, FindCUDA is deprecated and the proper way of using CUDA in CMake projects is enabling it via project() or enable_language()

https://cmake.org/cmake/help/v3.8/release/3.8.html#cuda

Answer 3

Maybe cuda was installed from sources (and nvcc is not in the path). Then the script can not set CUDA_TOOLKIT_ROOT_DIR because of 'nvcc' missing. For me it worked fine after a 'sudo apt install nvidia-cuda-toolkit'.

Answer 4

cmake mentioned CUDA_TOOLKIT_ROOT_DIR as cmake variable, not environment one. That's why it does not work when you put it into .bashrc. If you look into FindCUDA.cmake it clearly says that:

The script will prompt the user to specify CUDA_TOOLKIT_ROOT_DIR if the prefix cannot be determined by the location of nvcc in the system path and REQUIRED is specified to find_package(). To use a different installed version of the toolkit set the environment variable CUDA_BIN_PATH before running cmake (e.g. CUDA_BIN_PATH=/usr/local/cuda1.0 instead of the default /usr/local/cuda) or set CUDA_TOOLKIT_ROOT_DIR after configuring. If you change the value of CUDA_TOOLKIT_ROOT_DIR, various components that depend on the path will be relocated.

So put CUDA_BIN_PATH into .bashrc or specify CUDA_TOOLKIT_ROOT_DIR to cmake:

cmake -D CUDA_TOOLKIT_ROOT_DIR=/usr/local/cuda-5.5 ..

Answer 5

In terminal, type nano ~/.bashrc. Then add the following lines to the file:

export PATH=$PATH:/usr/local/cuda/bin
export LD_LIBRARY_PATH=$LD_LIBRARY_PATH:/usr/local/cuda/lib:/usr/local/lib
export CPLUS_INCLUDE_PATH=/usr/local/cuda/include

Save the file, then type source ~/.bashrc in terminal.

You may validate if CUDA path has been setup by typing nvcc --version in terminal.