Steps to link LIBNNP and PIMD:

(1) Get LIBNNP library of LIBNNP
    Copy src and Makefile to directory PIMDDIR/lib/libnnp.

(2) Go to directory PIMDDIR/lib/libnnp
    Edit Makefile
    Change "SRCDIR = src" to "SRCDIR = src_modified".

(3) Execute the patch file "apply_patch.sh"
    This should create "src_modified" that links to PIMD.

(4) Compile LIBNNP by "make parallel"
    This should create a file "lib/libnnp/libnnp.a".

(5) Go to directory PIMDDIR/compile
    Edit makefile
    Turn on the flag "-Dlibnnp" to link with libnnp.a.

(6) Compile PIMD as usual.

(7) Use pimd.mpi.x.

