Source code for hiphive.core.tensors

"""
Module containing tensor related functions
"""

import numpy as np


_paths = dict()


[docs] def rotation_tensor_as_matrix(R, order): einsum_input = [] for i in range(order): einsum_input.append(R) einsum_input.append([i, order + i]) R_tensor = np.einsum(*einsum_input) R_matrix = R_tensor.reshape((3**order, 3**order)) return R_matrix
[docs] def rotate_tensor_precalc(T, R): order = len(T.shape) return np.dot(T.ravel(), R).reshape((3,) * order)
[docs] def rotate_tensor(T, R, path=None): """Equivalent to T_abc... = T_ijk... R_ia R_jb R_kc ... """ order = len(T.shape) if order not in _paths: path = ['einsum_path', (0, 1)] for i in range(order - 1, 0, -1): path.append((0, i)) _paths[order] = path einsum_input = [T, list(range(order))] for i in range(order): einsum_input.append(R) einsum_input.append([i, order + i]) return np.einsum(*einsum_input, optimize=_paths[order])
[docs] def rotation_to_cart_coord(R, cell): """Return the rotation matrix in cart coord given a cell metric """ return np.dot(np.dot(cell.T, R), np.linalg.inv(cell.T))