Source code for qibo.backends.hamming_weight

"""Module defining the Hamming-weight-preserving backend."""

import inspect
from functools import cache

import qibo.backends._hamming_weight_operations as module
from qibo.config import raise_error


def HammingWeightBackend(platform=None):
    """Dynamically create a HammingWeightBackend class based on the selected backend."""

    from qibo.backends import construct_backend  # pylint: disable=C415

    if platform is None:
        from qibo.backends import (  # pylint: disable=C0415
            _check_backend,
            _get_engine_name,
        )

        platform = _get_engine_name(_check_backend(platform))

    backend = None  # needed for pylint
    if platform == "numpy":
        backend = construct_backend("numpy", platform=platform)
    elif platform in ("numba", "cupy", "cuquantum"):
        backend = construct_backend("qibojit", platform=platform)
    elif platform in ("tensorflow", "pytorch"):  # pragma: no cover
        backend = construct_backend("qiboml", platform=platform)
    else:  # pragma: no cover
        raise_error(
            NotImplementedError,
            f"Backend `{platform}` is not supported for "
            + "Hamming-weight-preserving circuit simulation.",
        )

    methods = {
        name: func for name, func in inspect.getmembers(module, inspect.isfunction)
    }

    for method_name in ["_get_cached_strings", "_get_lexicographical_order"]:
        if method_name in methods:
            methods[method_name] = cache(methods[method_name])

    HWBackend = type(
        "HammingWeightBackend", (backend.__class__,), methods
    )  # pylint: disable=E0606

    hw_backend = HWBackend()
    hw_backend.name = "hamming_weight"
    hw_backend.platform = platform

    hw_backend.calculate_full_probabilities = backend.calculate_probabilities

    hw_backend._dict_cached_strings_one = {}
    hw_backend._dict_cached_strings_two = {}

    hw_backend._dict_indexes = None

    hw_backend._transition_cache = {}
    hw_backend._local_index_cache = {}
    hw_backend._flat_cache = {}

    return hw_backend