ray/doc/source/tune/tutorials/tune-stopping.rst
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Stopping and Resuming Tune Trials
=================================
Ray Tune periodically checkpoints the experiment state so that it can be restarted when it fails or stops.
The checkpointing period is dynamically adjusted so that at least 95% of the time is used for handling
training results and scheduling.
If you send a SIGINT signal to the process running ``tune.run()`` (which is
usually what happens when you press Ctrl+C in the console), Ray Tune shuts
down training gracefully and saves a final experiment-level checkpoint.
Ray Tune also accepts the SIGUSR1 signal to interrupt training gracefully. This
should be used when running Ray Tune in a remote process (e.g. via Ray client)
as Ray will filter out SIGINT and SIGTERM signals per default.
How to resume a Tune run?
-------------------------
If you've stopped a run and and want to resume from where you left off,
you can then call ``tune.run()`` with ``resume=True`` like this:
.. code-block:: python
:emphasize-lines: 5
tune.run(
train,
# other configuration
name="my_experiment",
resume=True
)
You will have to pass a ``name`` if you are using ``resume=True`` so that Ray Tune can detect the experiment
folder (which is usually stored at e.g. ``~/ray_results/my_experiment``).
If you forgot to pass a name in the first call, you can still pass the name when you resume the run.
Please note that in this case it is likely that your experiment name has a date suffix, so if you
ran ``tune.run(my_trainable)``, the ``name`` might look like something like this:
``my_trainable_2021-01-29_10-16-44``.
You can see which name you need to pass by taking a look at the results table
of your original tuning run:
.. code-block::
:emphasize-lines: 5
== Status ==
Memory usage on this node: 11.0/16.0 GiB
Using FIFO scheduling algorithm.
Resources requested: 1/16 CPUs, 0/0 GPUs, 0.0/4.69 GiB heap, 0.0/1.61 GiB objects
Result logdir: /Users/ray/ray_results/my_trainable_2021-01-29_10-16-44
Number of trials: 1/1 (1 RUNNING)
Another useful option to know about is ``resume="AUTO"``, which will attempt to resume the experiment if possible,
and otherwise will start a new experiment.
For more details and other options for ``resume``, see the :ref:`Tune run API documentation <tune-run-ref>`.
.. _tune-stopping-ref:
How to stop Tune runs programmatically?
---------------------------------------
We've just covered the case in which you manually interrupt a Tune run.
But you can also control when trials are stopped early by passing the ``stop`` argument to ``tune.run``.
This argument takes, a dictionary, a function, or a :class:`Stopper <ray.tune.stopper.Stopper>` class as an argument.
If a dictionary is passed in, the keys may be any field in the return result of ``tune.report`` in the
Function API or ``step()`` (including the results from ``step`` and auto-filled metrics).
Stopping with a dictionary
~~~~~~~~~~~~~~~~~~~~~~~~~~
In the example below, each trial will be stopped either when it completes ``10`` iterations or when it
reaches a mean accuracy of ``0.98``.
These metrics are assumed to be **increasing**.
.. code-block:: python
# training_iteration is an auto-filled metric by Tune.
tune.run(
my_trainable,
stop={"training_iteration": 10, "mean_accuracy": 0.98}
)
Stopping with a function
~~~~~~~~~~~~~~~~~~~~~~~~
For more flexibility, you can pass in a function instead.
If a function is passed in, it must take ``(trial_id, result)`` as arguments and return a boolean
(``True`` if trial should be stopped and ``False`` otherwise).
.. code-block:: python
def stopper(trial_id, result):
return result["mean_accuracy"] / result["training_iteration"] > 5
tune.run(my_trainable, stop=stopper)
Stopping with a class
~~~~~~~~~~~~~~~~~~~~~
Finally, you can implement the :class:`Stopper <ray.tune.stopper.Stopper>` abstract class for stopping entire experiments. For example, the following example stops all trials after the criteria is fulfilled by any individual trial, and prevents new ones from starting:
.. code-block:: python
from ray.tune import Stopper
class CustomStopper(Stopper):
def __init__(self):
self.should_stop = False
def __call__(self, trial_id, result):
if not self.should_stop and result['foo'] > 10:
self.should_stop = True
return self.should_stop
def stop_all(self):
"""Returns whether to stop trials and prevent new ones from starting."""
return self.should_stop
stopper = CustomStopper()
tune.run(my_trainable, stop=stopper)
Note that in the above example the currently running trials will not stop immediately but will do so
once their current iterations are complete.
Ray Tune comes with a set of out-of-the-box stopper classes. See the :ref:`Stopper <tune-stoppers>` documentation.
Stopping after the first failure
--------------------------------
By default, ``tune.run`` will continue executing until all trials have terminated or errored.
To stop the entire Tune run as soon as **any** trial errors:
.. code-block:: python
tune.run(trainable, fail_fast=True)
This is useful when you are trying to setup a large hyperparameter experiment.