nf_fwrite2d.f90:(.text+0x82b): undefined reference to `netcdf_mp_nf90_put_var_1d_eightbytereal_'

This error message indicates that the linker is unable to find the definition of the subroutine "netcdf_mp_nf90_put_var_1d_eightbytereal_", which is required by the program nf_fwrite2d.f90.

The most likely cause of this error is that the NetCDF library is not properly installed or linked to the program. To resolve this error, you should check that the NetCDF library is installed and properly linked to the program.

You may need to add the library path and name to the linker command line options. For example, if the NetCDF library is installed in /usr/local/lib, you can add the following option to the linker command line:

-L/usr/local/lib -lnetcdff

This will tell the linker to search for the NetCDF library in /usr/local/lib and link it to the program.