hydra_pmi_proxy: error while loading shared libraries: libcr.so.0: cannot open shared object file: No such file or directory

if you encounter this error while running mpich
then install this:
$ sudo apt-get install libcr-dev

if you still facing this problem then you might not have configured your LD_LIBRARY_PATH and PATH correctly, then go to ~/.bashrc

you will see this line at the start of your bash:

[ -z "$PS1" ] && return

put you LD_LIBRRAY_PATH and PATH variable exports before this line.