# Copyright 2019 1QBit
#
# 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.
import numpy as np
[docs]def compute_integrals_fragment(mol, myhf):
"""
Compute the electronic integrals and store them in a data-structure that can be used
by MicrosoftQSharp backend
"""
from pyscf import gto, scf, fci, ao2mo
n_orbitals = len(myhf.mo_energy)
# One electron integrals: compute with PySCF, then thresholds and prepare for Microsoft data-structure
one_electron_compressed = myhf.mo_coeff.T @ myhf.get_hcore() @ myhf.mo_coeff
t1 = one_electron_compressed.reshape(n_orbitals, n_orbitals).astype(float)
t1_thresh = np.around(t1, decimals=6)
t1_bb = [([int(j+1), int(i+1)], t1_thresh[i, j])
for i in range(t1_thresh.shape[0]) for j in range(i, t1_thresh.shape[1])
if t1_thresh[i, j] != 0.]
# Two electron integrals: compute with PySCF, then thresholds and prepare for Microsoft data-structure
# The following occasionally returned a PySCF bug. It was replaced by the snippet below
#two_electron_compressed = ao2mo.kernel(mol, myhf.mo_coeff)
#t2 = ao2mo.restore(1, two_electron_compressed, n_orbitals)
twoint=myhf._eri
eri= ao2mo.restore(8,twoint,n_orbitals)
eri= ao2mo.incore.full(eri,myhf.mo_coeff)
t2 = ao2mo.restore(1,eri,n_orbitals)
# Store entries for non-zero integrals only if they are not a permutation
# of an existing entry
def is_two_body_permutation(coords1, coords2):
""" Test if coords are two-electorn permutations in mulliken convention """
return (
coords1 == [coords2[i] for i in [0, 1, 2, 3]] or
coords1 == [coords2[i] for i in [2, 3, 0, 1]] or
coords1 == [coords2[i] for i in [1, 0, 3, 2]] or
coords1 == [coords2[i] for i in [3, 2, 1, 0]] or
coords1 == [coords2[i] for i in [1, 0, 2, 3]] or
coords1 == [coords2[i] for i in [3, 2, 0, 1]] or
coords1 == [coords2[i] for i in [0, 1, 3, 2]] or
coords1 == [coords2[i] for i in [2, 3, 1, 0]])
t2_thresh = np.around(t2, decimals=6)
values, indices = [], []
for (coords, value) in np.ndenumerate(t2_thresh):
if value == 0.: continue
else :
coords = list(coords)
new_integral = True
for coords_ref in indices:
if is_two_body_permutation(coords_ref, coords):
new_integral = False
if new_integral:
values.append(value)
indices.append(coords)
# Convert two-electron integrals to Broombridge format
t2_bb = [[int(coord+1) for coord in coords] for coords in indices]
t2_bb = [(t2_bb[i], values[i]) for i in range(len(t2_bb))]
return t1_bb, t2_bb