Source code for flwr_datasets.partitioner.exponential_partitioner

# Copyright 2023 Flower Labs GmbH. All Rights Reserved.
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"""ExponentialPartitioner class."""


import numpy as np

from flwr_datasets.partitioner.size_partitioner import SizePartitioner


class ExponentialPartitioner(SizePartitioner):
    """Partitioner creates partitions of size that are correlated with exp(id).

    The amount of data each client gets is correlated with the exponent of partition ID.
    For instance, if the IDs range from 1 to M, client with ID 1 gets e units of
    data, client 2 gets e^2 units, and so on, up to client M which gets e^M units.
    The floor operation is applied on each of these numbers, it means floor(2.71...)
    = 2; e^2 ~ 7.39 floor(7.39) = 7. The number is rounded down = the fraction is
    always cut. The remainders of theses unassigned (fraction) samples is added to the
    biggest partition (the one with the biggest partition_id).

    Parameters
    ----------
    num_partitions : int
        The total number of partitions that the data will be divided into.
    """

    def __init__(self, num_partitions: int) -> None:
        super().__init__(num_partitions=num_partitions, partition_id_to_size_fn=np.exp)
        if num_partitions <= 0:
            raise ValueError("The number of partitions must be greater than zero.")