Internal change

pathwaysutils/elastic/manager.py

@@ -82,6 +82,18 @@ def __init__(
       max_elastic_down_event_count: int | None = None,
       max_reshard_retry_count: int | None = None,
   ) -> None:
+    """Initializes the manager.
+
+    Args:
+      devices: The devices to use. If None, jax.devices() is used.
+      reshard_check_period: The number of steps between reshard checks after a
+        slice down event has occurred.
+      snapshot_period: The number of steps between snapshots.
+      max_elastic_down_event_count: The maximum number of elastic down events.
+        If None, there is no limit.
+      max_reshard_retry_count: The maximum number of consequetive reshard
+        retries. If None, there is no limit.
+    """
     if devices is None:
       devices = jax.devices()
     self.devices = devices

pathwaysutils/elastic/simulated_manager.py

@@ -0,0 +1,99 @@
+# Copyright 2025 Google LLC
+#
+# 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
+#
+#      https://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.
+"""A simulated manager for elastic training.
+
+This module provides a simulated manager for elastic training. It can be used
+to test elastic training without needing to actually trigger elastic events.
+Instead, the user can control which slices are available at what times by
+calling `update_good_slice_indices`.
+"""
+
+import logging
+from typing import Sequence
+
+import jax
+from pathwaysutils.debug import timing
+from pathwaysutils.elastic import manager
+
+
+_logger = logging.getLogger(__name__)
+
+
+class SimulatedManager(manager.Manager):
+  """An elastic manager with settable slice availability.
+
+  This class can be used to modify which slices are marked as available by
+  overloading the `get_slice_availability` function.
+  """
+
+  _simulated_good_slice_indices: set[int]
+
+  def __init__(
+      self,
+      devices: Sequence[jax.Device],
+      reshard_check_period: int = 1,
+      snapshot_period: int = 1,
+      max_elastic_down_event_count: int | None = None,
+      max_reshard_retry_count: int | None = None,
+  ) -> None:
+    """Initializes the simulated manager.
+
+    Args:
+      devices: The devices to use. If None, jax.devices() is used.
+      reshard_check_period: The number of steps between reshard checks after a
+        slice down event has occurred.
+      snapshot_period: The number of steps between snapshots.
+      max_elastic_down_event_count: The maximum number of elastic down events.
+        If None, there is no limit.
+      max_reshard_retry_count: The maximum number of consequetive reshard
+        retries. If None, there is no limit.
+    """
+    self._simulated_good_slice_indices = set(d.slice_index for d in devices)
+
+    super().__init__(
+        devices,
+        snapshot_period,
+        reshard_check_period,
+        max_elastic_down_event_count,
+        max_reshard_retry_count,
+    )
+
+  def update_good_slice_indices(self, good_slice_indices: set[int]) -> None:
+    """Sets the good slice indices.
+
+    Subsequent calls to `get_slice_availability` will return these indices.
+
+    Args:
+      good_slice_indices: The simulated good slice indices.
+    """
+    self._simulated_good_slice_indices = good_slice_indices
+    _logger.debug(
+        "Updated: simumlated_good_slice_indices=%s",
+        self._simulated_good_slice_indices,
+    )
+
+  @timing.timeit
+  def get_slice_availability(self) -> set[int]:
+    """Returns the set of good slice indices.
+
+    Returns:
+      The set of good slice indices from the last call to
+      update_good_slice_indices. Returns an empty set if
+      update_good_slice_indices has not been called.
+    """
+    good_slice_indices = self._simulated_good_slice_indices
+
+    _logger.debug("good_slice_indices=%s", good_slice_indices)
+
+    return good_slice_indices