Invalid MEX-file '/scratch2/tmp_xin/ConvNetExp/MatConvNet/matlab/mex/vl_nnbnorm.mexa64': libcudart.s

I am compiling MatConvNet in GPU version. When I test it using vl_testnn, it shows me the following error:

Invalid MEX-file '/scratch2/tmp_xin/ConvNetExp/MatConvNet/matlab/mex/vl_nnbnorm.mexa64': cannot open shared object file: No such file or directory

I searched online, people say LD_LIBRARY_PATH and PATH should be changed. But I am not sure where they are.

Do you know what exactly the problem is for the error?