def to_dense(self):
self.tpmpo.IdL[0] = 0
self.tpmpo.IdR[-1] = 0 #How is this my job?
ed = ExactDiag.from_H_mpo(self.tpmpo)
ed.build_full_H_from_mpo()
nda = ed.full_H.to_ndarray()
if nda.shape[-1] == 1:
nda = nda[:, :, 0]
return nda
def test_ED():
# just quickly check that it runs without errors for a small system
xxz_pars = dict(L=4, Jxx=1., Jz=1., hz=0.0, bc_MPS='finite')
M = XXZChain(xxz_pars)
ED = ExactDiag(M)
ED.build_full_H_from_mpo()
H, ED.full_H = ED.full_H, None
ED.build_full_H_from_bonds()
H2 = ED.full_H
assert (npc.norm(H - H2, np.inf) < 1.e-14)
ED.full_diagonalization()
E, psi = ED.groundstate()
print("select charge_sector =", psi.qtotal)
assert np.all(psi.qtotal == [0])
E_sec2, psi_sec2 = ED.groundstate([2])
assert np.all(psi_sec2.qtotal == [2])
ED2 = ExactDiag(M, psi.qtotal)
ED2.build_full_H_from_mpo()
ED2.full_diagonalization()
E2, psi2 = ED2.groundstate()
full_psi2 = psi.zeros_like()
full_psi2[ED2._mask] = psi2
ov = npc.inner(psi, full_psi2, 'range', do_conj=True)
print("overlab <psi | psi2> = 1. -", 1. - ov)
assert (abs(abs(ov) - 1.) < 1.e-15)
# starting from a random guess in the correct charge sector,
# check if we can also do lanczos.
np.random.seed(12345)
psi3 = npc.Array.from_func(np.random.random,
psi2.legs,
qtotal=psi2.qtotal,
shape_kw='size')
E0, psi3, N = lanczos(ED2, psi3)
print("Lanczos E0 =", E0)
ov = npc.inner(psi3, psi2, 'range', do_conj=True)
print("overlab <psi2 | psi3> = 1. -", 1. - ov)
assert (abs(abs(ov) - 1.) < 1.e-15)
ED3 = ExactDiag.from_H_mpo(M.H_MPO)
ED3.build_full_H_from_mpo()
assert npc.norm(ED3.full_H - H, np.inf) < 1.e-14
