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from jax_md import space | |
from jax import custom_jvp | |
from jax import lax | |
periodic_displacement = space.periodic_displacement | |
pairwise_displacement = space.pairwise_displacement | |
periodic_shift = space.periodic_shift | |
f32 = np.float32 | |
def inverse(box): | |
if np.isscalar(box) or box.size == 1: | |
return 1 / box | |
elif box.ndim == 1: | |
return 1 / box | |
elif box.ndim == 2: | |
return np.linalg.inv(box) | |
raise ValueError() | |
def get_free_indices(n): | |
return ''.join([chr(ord('a') + i) for i in range(n)]) | |
def base_transform(box, R): | |
if np.isscalar(box) or box.size == 1: | |
return R * box | |
elif box.ndim == 1: | |
indices = get_free_indices(R.ndim - 1) + 'i' | |
return np.einsum(f'i,{indices}->{indices}', box, R) | |
elif box.ndim == 2: | |
free_indices = get_free_indices(R.ndim - 1) | |
left_indices = free_indices + 'j' | |
right_indices = free_indices + 'i' | |
return np.einsum(f'ij,{left_indices}->{right_indices}', box, R) | |
raise ValueError() | |
@custom_jvp | |
def transform_without_tangents(box, R): | |
return base_transform(box, R) | |
@transform_without_tangents.defjvp | |
def transform_without_tangents_jvp(primals, tangents): | |
box, R = primals | |
dbox, dR = tangents | |
return (transform_without_tangents(box, R), | |
dR + transform_without_tangents(dbox, R)) | |
def transform(box, R, fractional_coordinates=True): | |
if not fractional_coordinates: | |
return base_transform(box, R) | |
return transform_without_tangents(box, R) | |
def periodic_general(box, fractional_coordinates=True, wrapped=True): | |
inv_box = inverse(box) | |
def displacement_fn(Ra, Rb, **kwargs): | |
_box, _inv_box = box, inv_box | |
if 'box' in kwargs: | |
_box = kwargs['box'] | |
if not fractional_coordinates: | |
_inv_box = inverse(_box) | |
if 'new_box' in kwargs: | |
_box = kwargs['new_box'] | |
if not fractional_coordinates: | |
Ra = transform(_inv_box, Ra) | |
Rb = transform(_inv_box, Rb) | |
dR = periodic_displacement(f32(1.0), pairwise_displacement(Ra, Rb)) | |
return transform(_box, dR, fractional_coordinates=fractional_coordinates) | |
def u(R, dR): | |
if wrapped: | |
return periodic_shift(f32(1.0), R, dR) | |
return R + dR | |
def shift_fn(R, dR, **kwargs): | |
if not fractional_coordinates and not wrapped: | |
return R + dR | |
_box, _inv_box = box, inv_box | |
if 'box' in kwargs: | |
_box = kwargs['box'] | |
_inv_box = inverse(_box) | |
if 'new_box' in kwargs: | |
_box = kwargs['new_box'] | |
dR = transform(_inv_box, dR, fractional_coordinates=fractional_coordinates) | |
if not fractional_coordinates: | |
R = transform(_inv_box, R) | |
R = u(R, dR) | |
if not fractional_coordinates: | |
R = transform(_box, R) | |
return R | |
return displacement_fn, shift_fn |
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