# Python function that implements a loop of short runs
# calls back to LAMMPS via "lmp" instance
# lammps() must be called with ptr=lmpptr for this to work

def loop(N,cut0,thresh,lmpptr):
  print "LOOP ARGS",N,cut0,thresh,lmpptr
  from lammps import lammps
  lmp = lammps(ptr=lmpptr)
  natoms = lmp.get_natoms()
  
  for i in range(N):
    cut = cut0 + i*0.1

    lmp.set_variable("cut",cut)                 # set a variable in LAMMPS
    lmp.command("pair_style lj/cut ${cut}")     # LAMMPS command
    #lmp.command("pair_style lj/cut %d" % cut)  # LAMMPS command option

    lmp.command("pair_coeff * * 1.0 1.0")       # ditto
    lmp.command("run 10")                       # ditto
    pe = lmp.extract_compute("thermo_pe",0,0)   # extract total PE from LAMMPS
    print "PE",pe/natoms,thresh
    if pe/natoms < thresh: return