def plot_from_files(time, mpi_size, dt, input = False):
fig = plt.figure(figsize = (figsize_x, figsize_y))
colors = 'brcykgmk'
for rank in range (mpi_size):
# load particles
id, active, XY = IO.load_grid_of_particles(rank, time, input)
plt.scatter(XY[0,active], XY[1,active], marker = '.', s = 6, label = 'rank = %s' % rank, color = colors[rank])#label = 'rank = %s' % rank)#, linewidth = 1)# s = size
#plt.text(iter(['rank 0', 'rank 1', 'rank 2', 'rank 3']))
#plt.text(1.65, 0.9, 'rank = %s\n$t = %s$' % (rank, time), size = 36)
# print('rank', rank)
# print('x', XY[0,active])
# print('\n')
# print('y', XY[1,active])
plt.xlim(x_min, x_max)
plt.ylim(y_min, y_max)
plt.legend(scatterpoints = 1)
#plt.show()
plt.savefig(os.path.join('plots', 'allranks_particles_time%s_dt%s%s' % (time, dt, file_extension)))
# get initial positions, from file or random or other
# option 1: create from function
#ids, active, XY = IO.create_grid_of_particles(N = 10**2, w = 0.1)
# option 2: load from file
# set all particles initially to rank 0, so the other ranks will load empty arrays
# id_init, active_init, XY_init = IO.create_grid_of_particles(N = 10**2, w = 0.1)
# if rank == 0:
# IO.save_grid_of_particles(id_init, active_init, XY_init, t_0, rank, input = True)
# else:
# IO.save_empty_grid_to_input(t_0, rank)
# then load the particle grid for the given rank
ids, active, XY = IO.load_grid_of_particles(rank, time = 0, input = True)
if rank == 0:
Nparticles = np.sum(active)
# start at initial time
t = t_0
IO.save_grid_of_particles(ids, active, XY, t, rank)
#plot.plot(rank, XY[:,active], t, dt)
# main loop
print('\nstart time = %s' % t)
# Communicating, to avoid bad load balancing at the beginning
print('This is rank %s, communicating before mainloop' % (rank))
ids, XY, active = communication.exchange(comm, mpi_size, rank, ids, XY[0,:], XY[1,:], active)