Source code for tad_mctc.batch.mask.pairs

# This file is part of tad-mctc.
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# SPDX-Identifier: Apache-2.0
# Copyright (C) 2024 Grimme Group
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# 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
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#     http://www.apache.org/licenses/LICENSE-2.0
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# Unless required by applicable law or agreed to in writing, software
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"""
Batch Utility: Masks
====================

Functions for creating masks that discern between padding and actual values.
"""

from __future__ import annotations

import torch

from ...typing import Tensor
from .atoms import real_atoms

__all__ = ["real_pairs"]


# scripting or tracing does not improve performance


def real_pairs(numbers: Tensor, mask_diagonal: bool = True) -> Tensor:
    """
    Create a mask for pairs of atoms from atomic numbers, discerning padding
    and actual atoms. Padding value is zero.

    Parameters
    ----------
    numbers : Tensor
        Atomic numbers for all atoms.
    mask_diagonal : bool, optional
        Flag for also masking the diagonal, i.e., all pairs with the same
        indices. Defaults to `True`, i.e., writing False to the diagonal.

    Returns
    -------
    Tensor
        Mask for atom pairs that discerns padding and real atoms.
    """
    if mask_diagonal is True:
        return real_pairs_maskdiag(numbers)
    return real_pairs_no_maskdiag(numbers)



def real_pairs_maskdiag(numbers: Tensor) -> Tensor:
    """
    Create a mask for pairs of atoms from atomic numbers, discerning padding
    and actual atoms. Padding value is zero.

    Parameters
    ----------
    numbers : Tensor
        Atomic numbers for all atoms.

    Returns
    -------
    Tensor
        Mask for atom pairs that discerns padding and real atoms.
    """
    real = real_atoms(numbers)
    mask = real.unsqueeze(-2) * real.unsqueeze(-1)
    mask *= ~torch.diag_embed(torch.ones_like(real))
    return mask


def real_pairs_no_maskdiag(numbers: Tensor) -> Tensor:
    """
    Create a mask for pairs of atoms from atomic numbers, discerning padding
    and actual atoms. Padding value is zero.

    Parameters
    ----------
    numbers : Tensor
        Atomic numbers for all atoms.

    Returns
    -------
    Tensor
        Mask for atom pairs that discerns padding and real atoms.
    """
    real = real_atoms(numbers)
    return real.unsqueeze(-2) * real.unsqueeze(-1)