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Update docstrings in CreationCC wfn. #17

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Update docstrings in CreationCC wfn. #17

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115 changes: 95 additions & 20 deletions fanpy/wfn/creation_cc.py
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Original file line number Diff line number Diff line change
@@ -1,13 +1,70 @@
"""Creation Coupled-Cluster wavefunction."""
import numpy as np
from itertools import combinations

from fanpy.wfn.base import BaseWavefunction
from fanpy.tools import math_tools, slater
from fanpy.tools import slater


class CreationCC(BaseWavefunction):
r"""Creation Coupled-Cluster wavefunction.

The creation CC wavefunction is given by

.. math::
|\Psi \rangle = \exp(\sum_{ij}c_{ij}a^{\dagger}_i a^{\dagger}_j) | 0 \rangle

where :math: | 0 \rangle is the vacuum state, :math: a^{\dagger}_i is the creation operator
for the i-th spin orbital, and :math: c_{ij} are the parameters of the wavefunction.

Attributes
----------
nelec : int
Number of electrons.
nspin : int
Number of spin orbitals.
memory : {float, int, str, None}
Memory available for the wavefunction.
dict_orbpair_ind : dict of 2-tuple of int: int
Dictionary that maps orbital pairs to column indices.
dict_ind_orbpair : dict of int: 2-tuple of int
Dictionary that maps column indices to orbital pairs.
params : np.ndarray
Parameters of the wavefunction.
permutations : list of list of 2-tuple of int
Permutations of the orbital pairs.
signs : list of int
Signs of the permutations.

Methods
-------
__init__(nelec, nspin, memory=None, orbpairs=None, params=None)
Initialize the wavefunction.
assign_nelec(nelec)
Assign the number of electrons.
assign_params(params=None, add_noise=False)
Assign the parameters of the wavefunction.
assign_orbpairs(orbpairs=None)
Assign the orbital pairs used to construct the wavefunction.
get_col_ind(orbpair)
Get the column index that corresponds to the given orbital pair.
get_permutations()
Get the permutations of the given indices.
get_sign(indices)
Get the sign of the permutation of the given indices.
_olp(sd)
Calculate overlap with Slater determinant.
_olp_deriv(sd)
Calculate the derivative of the overlap.
get_overlap(sd, deriv=None) : {float, np.ndarray}
Return the (derivative) overlap of the wavefunction with a Slater determinant.
calculate_product(occ_indices, permutation, sign)
Calculate the product of the parameters of the given permutation.
"""

def __init__(self, nelec, nspin, memory=None, orbpairs=None, params=None):
""" Initialize the wavefunction
""" Initialize the wavefunction.

Parameters
----------
nelec : int
Expand All @@ -30,7 +87,7 @@ def __init__(self, nelec, nspin, memory=None, orbpairs=None, params=None):
self.assign_params(params=params)
self.permutations, self.signs = self.get_permutations()

def assign_nelec(self, nelec: int):
def assign_nelec(self, nelec):
"""Assign the number of electrons.

Parameters
Expand All @@ -55,6 +112,7 @@ def assign_nelec(self, nelec: int):

def assign_params(self, params=None, add_noise=False):
"""Assign the parameters of the creation cc wfn.

Parameters
----------
params : {np.ndarray, None}
Expand All @@ -80,7 +138,7 @@ def assign_params(self, params=None, add_noise=False):
super().assign_params(params=params, add_noise=add_noise)

def assign_orbpairs(self, orbpairs=None):
"""Assign the orbital pairs.
"""Assign the orbital pairs used to construct the creation CC wavefunction.

Parameters
----------
Expand Down Expand Up @@ -132,7 +190,7 @@ def assign_orbpairs(self, orbpairs=None):
self.dict_orbpair_ind = dict_orbpair_ind
self.dict_ind_orbpair = {i: orbpair for orbpair, i in dict_orbpair_ind.items()}

def get_col_ind(self, orbpair: tuple[int]):
def get_col_ind(self, orbpair):
"""Get the column index that corresponds to the given orbital pair.

Parameters
Expand Down Expand Up @@ -161,19 +219,16 @@ def get_col_ind(self, orbpair: tuple[int]):
)

def get_permutations(self):
"""Get the permutations of the given indices.

Parameters
----------
indices : list of int
Indices of the orbitals.
""" Calculate the permutations of indices 0 to nelec.

Returns
-------
perms : list of list of int
Permutations of the given indices.

Permutations of the indices (0 to nelec).
signs : list of int
Signs of the permutations.
"""

indices = np.arange(self.nelec, dtype=int)
perm_list = list(combinations(indices, r=2))

Expand All @@ -188,7 +243,7 @@ def get_permutations(self):
signs.append(self.get_sign(element))
return perms, signs

def get_sign(self, indices: list[int]):
def get_sign(self, indices):
"""Get the sign of the permutation of the given indices.

Parameters
Expand All @@ -210,7 +265,7 @@ def get_sign(self, indices: list[int]):
sign *= -1
return sign

def _olp(self, sd: int):
def _olp(self, sd):
""" Calculate overlap with Slater determinant.

Parameters
Expand All @@ -230,12 +285,29 @@ def _olp(self, sd: int):
return olp

def calculate_product(self, occ_indices, permutation, sign):
"""Calculate the product of the parameters of the given permutation.

Parameters
----------
occ_indices : list of int
Occupation indices of the Slater determinant.
permutation : list of 2-tuple of int
Permutation of the orbital pairs.
sign : int
Sign of the permutation.

Returns
-------
prod : float
Product of the parameters of the given permutation
"""

col_inds = list(map(self.get_col_ind, occ_indices.take(permutation)))
prod = sign*np.prod(self.params[col_inds])
return prod

def _olp_deriv(self, sd: int):
""" Calculate the derivative of the overlap
def _olp_deriv(self, sd):
""" Calculate the derivative of the overlap with a Slater determinant.

Parameters
----------
Expand All @@ -261,9 +333,11 @@ def _olp_deriv(self, sd: int):
return output


def get_overlap(self, sd: int, deriv=None):
"""Return the overlap of the wavefunction with a Slater determinant.
Inlcude math later.
def get_overlap(self, sd, deriv=None):
r"""Return the (derivative) overlap of the wavefunction with a Slater determinant.

.. math::
| \Psi \rangle = \sum_{\textbf{m} \in S} \sum_{\{i_1 j_1, ..., i_{n_m} j_{n_m} \} = \textbf{m}} sgn (\sigma(\{i_1 j_1, ..., i_{n_m} j_{n_m} \}))\prod_{k}^{n_m} c_{i_k j_k} | \textbf{m} \rangle

Parameters
----------
Expand All @@ -278,6 +352,7 @@ def get_overlap(self, sd: int, deriv=None):
overlap : {float, np.ndarray}
Overlap (or derivative of the overlap) of the wavefunction with the given Slater
determinant.

"""

if deriv is None:
Expand Down