#!/usr/bin/env python
# Copyright 2014-2019 The PySCF Developers. All Rights Reserved.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
#
# Author: Qiming Sun <osirpt.sun@gmail.com>
#
'''
Different FCI solvers are implemented to support different type of symmetry.
Symmetry
File Point group Spin singlet Real hermitian* Alpha/beta degeneracy
direct_spin0_symm Yes Yes Yes Yes
direct_spin1_symm Yes No Yes Yes
direct_spin0 No Yes Yes Yes
direct_spin1 No No Yes Yes
direct_uhf No No Yes No
direct_nosym No No No** Yes
* Real hermitian Hamiltonian implies (ij|kl) = (ji|kl) = (ij|lk) = (ji|lk)
** Hamiltonian is real but not hermitian, (ij|kl) != (ji|kl) ...
'''
import sys
import ctypes
import numpy
from pyscf import lib
from pyscf import ao2mo
from pyscf.lib import logger
from pyscf import symm
from pyscf.scf.hf_symm import map_degeneracy
from pyscf.fci import cistring
from pyscf.fci import direct_spin0
from pyscf.fci import direct_spin1
from pyscf.fci import direct_spin1_symm
from pyscf.fci import addons
from pyscf import __config__
libfci = direct_spin1.libfci
[docs]
def contract_2e(eri, fcivec, norb, nelec, link_index=None, orbsym=None, wfnsym=0):
link_index = direct_spin1._unpack(norb, nelec, link_index)
if isinstance(link_index, numpy.ndarray):
# For backward compatibility
link_index = (link_index, link_index)
return direct_spin1_symm.contract_2e(eri, fcivec, norb, nelec, link_index,
orbsym, wfnsym)
energy = direct_spin1_symm.energy
kernel = direct_spin1_symm.kernel
make_rdm1 = direct_spin0.make_rdm1
make_rdm1s = direct_spin0.make_rdm1s
make_rdm12 = direct_spin0.make_rdm12
trans_rdm1s = direct_spin0.trans_rdm1s
trans_rdm1 = direct_spin0.trans_rdm1
trans_rdm12 = direct_spin0.trans_rdm12
[docs]
def get_init_guess(norb, nelec, nroots, hdiag, orbsym, wfnsym=0):
neleca, nelecb = direct_spin1._unpack_nelec(nelec)
assert (neleca == nelecb)
strsa = cistring.gen_strings4orblist(range(norb), neleca)
na = len(strsa)
airreps = direct_spin1_symm._gen_strs_irrep(strsa, orbsym)
sym_allowed = (airreps[:,None] ^ airreps) == wfnsym
idx = numpy.arange(na)
sym_allowed[idx[:,None] < idx] = False
idx_a, idx_b = numpy.where(sym_allowed)
hdiag = hdiag.reshape(na,na)[idx_a,idx_b]
if hdiag.size <= nroots:
hdiag_indices = numpy.arange(hdiag.size)
else:
hdiag_indices = numpy.argpartition(hdiag, nroots-1)[:nroots]
ci0 = []
for k in hdiag_indices:
addra, addrb = idx_a[k], idx_b[k]
x = numpy.zeros((na, na))
if addra == addrb:
x[addra,addrb] = 1
else:
x[addra,addrb] = x[addrb,addra] = numpy.sqrt(.5)
ci0.append(x.ravel().view(direct_spin1.FCIvector))
if len(ci0) == 0:
raise lib.exceptions.WfnSymmetryError(
f'Initial guess for symmetry {wfnsym} not found')
return ci0
[docs]
def get_init_guess_cyl_sym(norb, nelec, nroots, hdiag, orbsym, wfnsym=0):
neleca, nelecb = direct_spin1._unpack_nelec(nelec)
na = cistring.num_strings(norb, neleca)
ci0_guess = direct_spin1_symm.get_init_guess_cyl_sym(
norb, nelec, nroots, hdiag, orbsym, wfnsym)
ci0 = []
for x in ci0_guess:
x = x.reshape(na, na)
x = x + x.T
norm = numpy.linalg.norm(x)
if norm < 1e-3:
continue
x *= 1./norm
ci0.append(x.ravel().view(direct_spin1.FCIvector))
if len(ci0) == 0:
raise lib.exceptions.WfnSymmetryError(
f'Initial guess for symmetry {wfnsym} not found')
return ci0
[docs]
class FCISolver(direct_spin0.FCISolver):
_keys = {'wfnsym', 'sym_allowed_idx'}
davidson_only = getattr(__config__, 'fci_direct_spin1_symm_FCI_davidson_only', True)
pspace_size = getattr(__config__, 'fci_direct_spin1_symm_FCI_pspace_size', 400)
def __init__(self, mol=None, **kwargs):
# wfnsym will be guessed based on initial guess if it is None
self.wfnsym = None
self.sym_allowed_idx = None
direct_spin0.FCISolver.__init__(self, mol, **kwargs)
absorb_h1e = direct_spin1.FCISolver.absorb_h1e
dump_flags = direct_spin1_symm.FCISolver.dump_flags
make_hdiag = direct_spin1_symm.FCISolver.make_hdiag
pspace = direct_spin1_symm.FCISolver.pspace
contract_1e = direct_spin1_symm.FCISolver.contract_1e
contract_ss = direct_spin1_symm.FCISolver.contract_ss
guess_wfnsym = direct_spin1_symm.guess_wfnsym
kernel = direct_spin1_symm.FCISolver.kernel
[docs]
def contract_2e(self, eri, fcivec, norb, nelec, link_index=None,
orbsym=None, wfnsym=None, **kwargs):
if orbsym is None: orbsym = self.orbsym
if wfnsym is None: wfnsym = self.wfnsym
wfnsym = direct_spin1_symm._id_wfnsym(self, norb, nelec, orbsym, wfnsym)
nelec = direct_spin1._unpack_nelec(nelec, self.spin)
civec = contract_2e(eri, fcivec, norb, nelec, link_index, orbsym, wfnsym)
na = cistring.num_strings(norb, nelec[0])
if civec.size != na**2:
s_idx = numpy.hstack(self.sym_allowed_idx)
x, y = divmod(s_idx, na)
ci1 = numpy.empty(na**2)
ci1[y*na+x] = civec
civec += ci1[s_idx]
civec *= .5
else:
civec = lib.transpose_sum(civec.reshape(na,na), inplace=True)
civec *= .5
return civec
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def get_init_guess(self, norb, nelec, nroots, hdiag, orbsym=None, wfnsym=None):
if orbsym is None: orbsym = self.orbsym
if wfnsym is None:
wfnsym = direct_spin1_symm._id_wfnsym(
self, norb, nelec, orbsym, self.wfnsym)
s_idx = numpy.hstack(self.sym_allowed_idx)
if getattr(self.mol, 'groupname', None) in ('Dooh', 'Coov'):
ci0 = get_init_guess_cyl_sym(
norb, nelec, nroots, hdiag, orbsym, wfnsym)
else:
nelec = direct_spin1._unpack_nelec(nelec, self.spin)
na = cistring.num_strings(norb, nelec[0])
if hdiag.size != na * na:
hdiag, hdiag0 = numpy.empty(na*na), hdiag
hdiag[:] = 1e9
hdiag[numpy.hstack(self.sym_allowed_idx)] = hdiag0
ci0 = get_init_guess(norb, nelec, nroots, hdiag.ravel(),
orbsym, wfnsym)
return [x[s_idx] for x in ci0]
FCI = FCISolver
