Hi, I am not able to install the GROMACS 2021 version on my Linux machine based on ubuntu distribution. If someone guides me then its would be help full. Here is the screenshot of my machine, installed Cuda cores on NVIDIA GPU.
The error I see in the screenshot is already telling you the problem, that is
-DGMX_GPU=ON
is not correct, you have to pick one of the options as stated in the error, i.e. OFF, CUDA, OpenCL or SYCL.
Clean the build directory and start again and select -DGMX_GPU=CUDA (given that you have cuda installed) in your cmake command.
Moreover, I am not sure those commands for gcc and g++ will work properly. If the proper gcc/g++ versions are already sourced (try gcc --version and g++ --version on your terminal) then you do not need to specify anything, otherwise you will have to point out the whole path (e.g. -DMAKE_C_COMPILER=/usr/bin/gcc).
Why are you setting to OFF the FFTW library? Is it already installed in your machine?
And why are you setting to off the download of the regression test? I see that you are pointing it towards a local directory, which is fine, but from the names it seems that you are installing a 2021 version and pointing to a 2020 regression test, which is not.
I answered something similar time ago, give it a read, maybe it will help you