def spin1_lanczos(D, nsite, Jz=1.0, k=1, target_block=None, periodic=False):
"""test for directly construct and solve the ground state energy."""
model = Spin1Model2(J=1, Jz=Jz, D=D, nsite=nsite, periodic=periodic)
hgen = RGHGen(
spaceconfig=model.spaceconfig, H=model.H_serial, evolutor_type="null" if target_block is None else "normal"
)
if target_block is None:
H = get_H(hgen=hgen)
Emin, Evec = _eigsh(H, k=k)
elif isinstance(target_block, (tuple, list)):
assert k == 1
H0, bm2 = get_H_bm(hgen=hgen, bstr="M")
EL, VL = [], []
for tb in target_block:
H = bm2.lextract_block(H0, (tb, tb))
Ei, Vi = _eigsh(H, k=1)
EL.append(Ei)
VL.append(Vi)
# print H-H.T.conj()
# pdb.set_trace()
Emin = concatenate(EL)
Evec = None # concatenate(VL,axis=1)
else:
H, bm2 = get_H_bm(hgen=hgen, bstr="M")
H = bm2.lextract_block(H, (target_block, target_block))
Emin, Evec = _eigsh(H, k=k)
print "The Ground State Energy is %s" % Emin
return Emin, Evec
def get_mps(K,Jp,J1=1.,J2=0.2412,nsite=30,which='finite',data_file=None):
'''
Run finite-DMFT/lanczos for two impurity Kondo model to get the Ground state energy.
Parameters:
:J1/J2/K/Jp: float, the parameters defining the model.
:nsite: integer, the number of sites, must be even.
:which: 'finite'/'lanczos', select the method to solve the chain, 'finite dmrg' or 'lanczos'.
'''
assert(which=='finite' or which=='lanczos')
assert(nsite%2==0)
model=TIKM(J1=J1,J2=J2,K=K,Jp=Jp,nsite=nsite)
hgen=SpinHGen(spaceconfig=model.spaceconfig,evolutor=MaskedEvolutor(hndim=model.spaceconfig.hndim) if which=='finite' else NullEvolutor(hndim=2))
dmrgegn=DMRGEngine(hchain=model.H_serial,hgen=hgen,tol=0)
if which=='lanczos':
H=get_H(H=model.H_serial,hgen=hgen)
EG,EV=eigsh(H,k=1)
mps=state2MPS(EV[:,0])
else:
EG=dmrgegn.run_finite(endpoint=(2,'<-',0),maxN=[10,20],tol=0)[-1]
mps=dmrgegn.get_mps(direction='<-') #right normalized initial state
if data_file is not None:
mps.save(data_file)
return mps
