def build_initial_state(size, states, filling, mode='random', seed=None):
warnings.warn(
"Deprecated `build_initial_state`: Use `tenpy.networks.mps.InitialStateBuilder` instead.",
category=FutureWarning,
stacklevel=2)
from tenpy.networks import mps
return mps.build_initial_state(size, states, filling, mode, seed)
def random_list(length,upfilling,dnfilling):
"""this function generates random occupations for an initial state
of the requested length
with densities of upfilling, dnfilling for the up and down spins,
respectively
A corresponding product state MPS is returned."""
uplist = build_initial_state(size=length,states=(0,1),filling=(1-upfilling,upfilling))
dnlist = build_initial_state(size=length,states=(0,1),filling=(1-dnfilling,dnfilling))
prod=[]
for i in range(length):
if (uplist[i]==0 and dnlist[i]==0):
prod.append("empty")
elif (uplist[i]==1 and dnlist[i]==0):
prod.append("up")
elif (uplist[i]==0 and dnlist[i]==1):
prod.append("down")
elif (uplist[i]==1 and dnlist[i]==1):
prod.append("full")
return prod
def dmrg_wrapper(model_par,
sim_par,
run_par,
args,
psi=None,
sim_filename=None,
reload_sim=False):
"""Run DMRG ("Walk this way...").
Args:
model_par (dict): Model parameters
args (Namespace): All command line options
psi (MPS, optional): Initial state. If None, random state is iinitialized based on model_par and args.
Returns:
psi (MPS): Ground state
out (dict): DMRG output
num_ini (array): Density profile for the initial state
M (model): model
"""
print("chi's in use:", sim_par['CHI_LIST'])
print("minimum no. of sweeps:", sim_par['MIN_STEPS'])
print('dmrg_wrapper has bc={}'.format(model_par['bc_MPS']))
# Check if there is already a data file from a finished run
try:
with open('fh_dmrg_' + sim_par['identifier'] + '.dat', 'rb') as f:
a = pickle.load(f)
if data['out']['shelve_flag']:
print("Simulation was shelved. Restarting soon.")
else:
print("Finished data file found. Skipping.")
print('Check for {skip:True}')
return None, {
'skip': True
}, None, None, None # Not very clean but haven't found anything better
except IOError:
print("No data file found. Starting new sim.")
pass
if reload_sim:
with open(sim_filename + '.sim', 'rb') as f:
save_sim = pickle.load(f)
sim_par[
'STARTING_ENV_FROM_PSI'] = 0 # Make sure to use old environments.
sim_par['CHI_LIST'] = {
0: max(sim_par['CHI_LIST'].values())
} # Assume saved sim had reached max chi.
sim_par['MIN_STEPS'] = 20
sim_par['LP'] = save_sim['LP']
sim_par['RP'] = save_sim['RP']
psi = save_sim['psi']
M = save_sim['M']
num_ini = save_sim['num_ini']
initial_state = save_sim['initial_state']
else:
M = mod.HofstadterFermions(model_par)
initial_state = build_initial_state(
M.lat.N_sites, (0, 1),
(1 - run_par['filling'], run_par['filling']),
mode='random',
seed=args.seed)
if psi == None:
print("Generating new psi.")
#L = model_par['Lx'] * model_par['Ly']
# upfilling, dnfilling = get_filling(run_par, L)
# prod = random_list(L, upfilling, dnfilling)
psi = MPS.from_product_state(M.lat.mps_sites(),
initial_state,
bc=model_par['bc_MPS'])
else:
print("Using user-specified psi.")
num_ini = psi.expectation_value('N')
print('Initial density profile:', num_ini)
t0 = time.time()
print("Starting DMRG...")
out = dmrg.run(psi, M, sim_par)
print("DMRG took {} seconds.".format(time.time() - t0))
out['time'] = time.time() - t0
# sim = simulation.simulation(psi, M)
# sim.dmrg_par = sim_par
# sim.ground_state()
# out = sim.sim_stats[-1]
# if out['shelve_flag']: # DMRG did not end before time ran out; save sim to disk
# save_sim = {
# 'LP': out['LP'],
# 'RP': out['RP'],
# 'psi': psi,
# 'M': M,
# 'num_ini': num_ini,
# 'initial_state': initial_state,
# 'model_par': model_par,
# 'sim_par': sim_par,
# }
# with open('fh_dmrg_' + identifier + '.sim', 'wb') as f:
# pickle.dump(save_sim, f)
out['skip'] = False
return psi, out, num_ini, M, initial_state
