feat(datasets) Add inner class constrained partitioner

datasets/flwr_datasets/partitioner/inner_class_constrained.py

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+# # Copyright 2024 Flower Labs GmbH. All Rights Reserved.
+# #
+# # 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
+# #
+# #     http://www.apache.org/licenses/LICENSE-2.0
+# #
+# # Unless required by applicable law or agreed to in writing, software
+# # distributed under the License is distributed on an "AS IS" BASIS,
+# # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# # See the License for the specific language governing permissions and
+# # limitations under the License.
+# # ==============================================================================
+# """InnerClassConstrained partitioner class."""
+import warnings
+from typing import Dict, List, Optional, Union
+
+import numpy as np
+
+import datasets
+from datasets import Dataset
+
+from flwr_datasets.common.typing import NDArrayFloat, NDArrayInt
+from flwr_datasets.partitioner import Partitioner
+from flwr_datasets.partitioner.inner_probability_partitioner import \
+    InnerProbabilityPartitioner
+
+
+class InnerClassConstrainedPartitioner(Partitioner):
+
+    def __init__(self, partition_by: str, num_classes_per_partition: int,
+                 partition_sizes: Optional[Union[NDArrayInt, List[int]]]):
+        super().__init__()
+        self._partition_by = partition_by
+        self._num_classes_per_partition = num_classes_per_partition
+        self._partition_sizes = partition_sizes
+        self._inner_prob_partitioner: Optional[InnerProbabilityPartitioner] = None
+        self._inner_prob_setup = False
+
+    def load_partition(self, partition_id: int) -> Dataset:
+        # create the partition sizes
+        self._setup_inner_prob_if_needed()
+        return self._inner_prob_partitioner.load_partition(partition_id=partition_id)
+
+    def _setup_inner_prob_if_needed(self):
+        if not self._inner_prob_setup:
+            num_unique_labels = self.dataset.unique(self._partition_by)
+
+            # todo: some sanity checks
+            per_partition_per_label_prob = 1.0 / self._num_classes_per_partition
+            prob_per_partition = ([
+                                     per_partition_per_label_prob] *
+                                  self._num_classes_per_partition + [
+                                     0.0] * (
+                                             len(num_unique_labels) -
+                                             self._num_classes_per_partition))
+
+            num_partitions = len(self._partition_sizes)
+            probs = []
+            for i in range(num_partitions):
+                prob = prob_per_partition.copy()
+                np.random.shuffle(prob)
+                probs.append(prob)
+            self._inner_prob_partitioner = InnerProbabilityPartitioner(
+                self._partition_by, probabilities=np.array(probs),
+                partition_sizes=self._partition_sizes)
+            self._inner_prob_partitioner.dataset = self.dataset
+            self._inner_prob_setup = True
+
+    @property
+    def num_partitions(self) -> int:
+        return self._inner_prob_partitioner.num_partitions