import sys

from ase.build import molecule
from ase.optimize import BFGS
from ase.calculators.espresso import Espresso
from ase.calculators.socketio import SocketIOCalculator

atoms = molecule('H2O', vacuum=3.0)
atoms.rattle(stdev=0.1)

# Environment-dependent parameters (please configure before running):
pseudopotentials = {'H': 'H.pbe-rrkjus.UPF',
                    'O': 'O.pbe-rrkjus.UPF'}
pseudo_dir = '.'

# In this example we use a UNIX socket.  See other examples for INET socket.
# UNIX sockets are faster then INET sockets, but cannot run over a network.
# UNIX sockets are files.  The actual path will become /tmp/ipi_ase_espresso.
unixsocket = 'ase_espresso'

# Configure pw.x command for UNIX or INET.
#
# UNIX: --ipi {unixsocket}:UNIX
# INET: --ipi {host}:{port}
#
# See also QE documentation, e.g.:
#
#    https://www.quantum-espresso.org/Doc/pw_user_guide/node13.html
#
command = ('pw.x < PREFIX.pwi --ipi {unixsocket}:UNIX > PREFIX.pwo'
           .format(unixsocket=unixsocket))

espresso = Espresso(command=command,
                    ecutwfc=30.0,
                    pseudopotentials=pseudopotentials,
                    pseudo_dir=pseudo_dir)

opt = BFGS(atoms, trajectory='opt.traj',
           logfile='opt.log')

with SocketIOCalculator(espresso, log=sys.stdout,
                        unixsocket=unixsocket) as calc:
    atoms.calc = calc
    opt.run(fmax=0.05)

# Note: QE does not generally quit cleanly - expect nonzero exit codes.