Cloning

Clonable

A base class allowing inheriting classes define how they should be cloned.

Any class inheriting from Clonable gains these behaviors: (i) A new method named .clone() becomes available; (ii) __deepcopy__ and __copy__ work as aliases for .clone(); (iii) A new method, _get_cloned_state(self, *, memo: dict) is now defined and needs to be implemented by the inheriting class.

The method _get_cloned_state(...) expects a dictionary named memo, which maps from the ids of already cloned objects to their clones. If _get_cloned_state(...) is to use deep_clone(...) or deepcopy(...) within itself, this memo dictionary can be passed to these functions. The return value of _get_cloned_state(...) is a dictionary, which will be used as the __dict__ of the newly made clone.

Source code in evotorch/tools/cloning.py

class Clonable:
    """
    A base class allowing inheriting classes define how they should be cloned.

    Any class inheriting from Clonable gains these behaviors:
    (i) A new method named `.clone()` becomes available;
    (ii) `__deepcopy__` and `__copy__` work as aliases for `.clone()`;
    (iii) A new method, `_get_cloned_state(self, *, memo: dict)` is now
    defined and needs to be implemented by the inheriting class.

    The method `_get_cloned_state(...)` expects a dictionary named `memo`,
    which maps from the ids of already cloned objects to their clones.
    If `_get_cloned_state(...)` is to use `deep_clone(...)` or `deepcopy(...)`
    within itself, this `memo` dictionary can be passed to these functions.
    The return value of `_get_cloned_state(...)` is a dictionary, which will
    be used as the `__dict__` of the newly made clone.
    """

    def _get_cloned_state(self, *, memo: dict) -> dict:
        raise NotImplementedError

    def clone(self, *, memo: Optional[dict] = None) -> "Clonable":
        """
        Get a clone of this object.

        Args:
            memo: Optionally a dictionary which maps from the ids of the
                already cloned objects to their clones. In most scenarios,
                when this method is called from outside, this can be left
                as None.
        Returns:
            The clone of the object.
        """
        if memo is None:
            memo = {}

        self_id = id(self)
        if self_id in memo:
            return memo[self_id]

        new_object = object.__new__(type(self))
        memo[id(self)] = new_object

        new_object.__dict__.update(self._get_cloned_state(memo=memo))
        return new_object

    def __copy__(self) -> "Clonable":
        return self.clone()

    def __deepcopy__(self, memo: Optional[dict]):
        if memo is None:
            memo = {}
        return self.clone(memo=memo)

clone(self, *, memo=None)

Get a clone of this object.

Parameters:

Name	Type	Description	Default
memo	Optional[dict]	Optionally a dictionary which maps from the ids of the already cloned objects to their clones. In most scenarios, when this method is called from outside, this can be left as None.	None

Returns:

Type	Description
Clonable	The clone of the object.

Source code in evotorch/tools/cloning.py

def clone(self, *, memo: Optional[dict] = None) -> "Clonable":
    """
    Get a clone of this object.

    Args:
        memo: Optionally a dictionary which maps from the ids of the
            already cloned objects to their clones. In most scenarios,
            when this method is called from outside, this can be left
            as None.
    Returns:
        The clone of the object.
    """
    if memo is None:
        memo = {}

    self_id = id(self)
    if self_id in memo:
        return memo[self_id]

    new_object = object.__new__(type(self))
    memo[id(self)] = new_object

    new_object.__dict__.update(self._get_cloned_state(memo=memo))
    return new_object

ReadOnlyClonable (Clonable)

Clonability base class for read-only and/or immutable objects.

This is a base class specialized for the immutable containers of EvoTorch. These immutable containers have two behaviors for cloning: one where the read-only attribute is preserved and one where a mutable clone is created.

Upon being copied or deep-copied (using the standard Python functions), the newly made clones are also read-only. However, when copied using the clone(...) method, the newly made clone is mutable by default (unless the clone(...) method was used with preserve_read_only=True). This default behavior of the clone(...) method was inspired by the copy() method of numpy arrays (the inspiration being that the .copy() of a read-only numpy array will not be read-only anymore).

Subclasses of evotorch.immutable.ImmutableContainer inherit from ReadOnlyClonable.

Source code in evotorch/tools/cloning.py

class ReadOnlyClonable(Clonable):
    """
    Clonability base class for read-only and/or immutable objects.

    This is a base class specialized for the immutable containers of EvoTorch.
    These immutable containers have two behaviors for cloning:
    one where the read-only attribute is preserved and one where a mutable
    clone is created.

    Upon being copied or deep-copied (using the standard Python functions),
    the newly made clones are also read-only. However, when copied using the
    `clone(...)` method, the newly made clone is mutable by default
    (unless the `clone(...)` method was used with `preserve_read_only=True`).
    This default behavior of the `clone(...)` method was inspired by the
    `copy()` method of numpy arrays (the inspiration being that the `.copy()`
    of a read-only numpy array will not be read-only anymore).

    Subclasses of `evotorch.immutable.ImmutableContainer` inherit from
    `ReadOnlyClonable`.
    """

    def _get_mutable_clone(self, *, memo: dict) -> Any:
        raise NotImplementedError

    def clone(self, *, memo: Optional[dict] = None, preserve_read_only: bool = False) -> Any:
        """
        Get a clone of this read-only object.

        Args:
            memo: Optionally a dictionary which maps from the ids of the
                already cloned objects to their clones. In most scenarios,
                when this method is called from outside, this can be left
                as None.
            preserve_read_only: Whether or not to preserve the read-only
                behavior in the clone.
        Returns:
            The clone of the object.
        """
        if memo is None:
            memo = {}
        if preserve_read_only:
            return super().clone(memo=memo)
        else:
            return self._get_mutable_clone(memo=memo)

    def __copy__(self) -> Any:
        return self.clone(preserve_read_only=True)

    def __deepcopy__(self, memo: Optional[dict]) -> Any:
        if memo is None:
            memo = {}
        return self.clone(memo=memo, preserve_read_only=True)

clone(self, *, memo=None, preserve_read_only=False)

Get a clone of this read-only object.

Parameters:

Name	Type	Description	Default
memo	Optional[dict]	Optionally a dictionary which maps from the ids of the already cloned objects to their clones. In most scenarios, when this method is called from outside, this can be left as None.	None
preserve_read_only	bool	Whether or not to preserve the read-only behavior in the clone.	False

Returns:

Type	Description
Any	The clone of the object.

Source code in evotorch/tools/cloning.py

def clone(self, *, memo: Optional[dict] = None, preserve_read_only: bool = False) -> Any:
    """
    Get a clone of this read-only object.

    Args:
        memo: Optionally a dictionary which maps from the ids of the
            already cloned objects to their clones. In most scenarios,
            when this method is called from outside, this can be left
            as None.
        preserve_read_only: Whether or not to preserve the read-only
            behavior in the clone.
    Returns:
        The clone of the object.
    """
    if memo is None:
        memo = {}
    if preserve_read_only:
        return super().clone(memo=memo)
    else:
        return self._get_mutable_clone(memo=memo)

Serializable (Clonable)

Base class allowing the inheriting classes become Clonable and picklable.

Any class inheriting from Serializable becomes Clonable (since Serializable is a subclass of Clonable) and therefore is expected to define its own _get_cloned_state(...) (see the documentation of the class Clonable for details).

A Serializable class gains a behavior for its __getstate__. In this already defined and implemented __getstate__ method, the resulting dictionary of _get_cloned_state(...) is used as the state dictionary. Therefore, for Serializable objects, the behavior defined in their _get_cloned_state(...) methods affect how they are pickled.

Classes inheriting from Serializable are evotorch.Problem, evotorch.Solution, evotorch.SolutionBatch, and evotorch.distributions.Distribution. In their _get_cloned_state(...) implementations, these classes use deep_clone(...) on themselves to make sure that their contained PyTorch tensors are copied using the .clone() method, ensuring that those tensors are detached from their old storages during the cloning operation. Thanks to being Serializable, their contained tensors are detached from their old storages both at the moment of copying/cloning AND at the moment of pickling.

Source code in evotorch/tools/cloning.py

class Serializable(Clonable):
    """
    Base class allowing the inheriting classes become Clonable and picklable.

    Any class inheriting from `Serializable` becomes `Clonable` (since
    `Serializable` is a subclass of `Clonable`) and therefore is expected to
    define its own `_get_cloned_state(...)` (see the documentation of the
    class `Clonable` for details).

    A `Serializable` class gains a behavior for its `__getstate__`. In this
    already defined and implemented `__getstate__` method, the resulting
    dictionary of `_get_cloned_state(...)` is used as the state dictionary.
    Therefore, for `Serializable` objects, the behavior defined in their
    `_get_cloned_state(...)` methods affect how they are pickled.

    Classes inheriting from `Serializable` are `evotorch.Problem`,
    `evotorch.Solution`, `evotorch.SolutionBatch`, and
    `evotorch.distributions.Distribution`. In their `_get_cloned_state(...)`
    implementations, these classes use `deep_clone(...)` on themselves to make
    sure that their contained PyTorch tensors are copied using the `.clone()`
    method, ensuring that those tensors are detached from their old storages
    during the cloning operation. Thanks to being `Serializable`, their
    contained tensors are detached from their old storages both at the moment
    of copying/cloning AND at the moment of pickling.
    """

    def __getstate__(self) -> dict:
        memo = {id(self): self}
        return self._get_cloned_state(memo=memo)

deep_clone(x, *, otherwise_deepcopy=False, otherwise_return=False, otherwise_fail=False, memo=None)

A recursive cloning function similar to the standard deepcopy.

The difference between deep_clone(...) and deepcopy(...) is that deep_clone(...), while recursively traversing, will run the .clone() method on the PyTorch tensors it encounters, so that the cloned tensors are forcefully detached from their storages (instead of cloning those storages as well).

At the moment of writing this documentation, the current behavior of PyTorch tensors upon being deep-copied is to clone themselves AND their storages. Therefore, if a PyTorch tensor is a slice of a large tensor (which has a large storage), then the large storage will also be deep-copied, and the newly made clone of the tensor will point to a newly made large storage. One might instead prefer to clone tensors in such a way that the newly made tensor points to a newly made storage that contains just enough data for the tensor (with the unused data being dropped). When such a behavior is desired, one can use this deep_clone(...) function.

Upon encountering a read-only and/or immutable data, this function will NOT modify the read-only behavior. For example, the deep-clone of a ReadOnlyTensor is still a ReadOnlyTensor, and the deep-clone of a read-only numpy array is still a read-only numpy array. Note that this behavior is different than the clone() method of a ReadOnlyTensor and the copy() method of a numpy array. The reason for this protective behavior is that since this is a deep-cloning operation, the encountered tensors and/or arrays might be the components of the root object, and changing their read-only attributes might affect the integrity of this root object.

The deep_clone(...) function needs to know what to do when an object of unrecognized type is encountered. Therefore, the user is expected to set one of these arguments as True (and leave the others as False): otherwise_deepcopy, otherwise_return, otherwise_fail.

Parameters:

Name	Type	Description	Default
x	Any	The object which will be deep-cloned. This object can be a standard Python container (i.e. list, tuple, dict, set), an instance of Problem, Solution, SolutionBatch, ObjectArray, ImmutableContainer, Clonable, and also any other type of object if either the argument otherwise_deepcopy or the argument otherwise_return is set as True.	required
otherwise_deepcopy	bool	Setting this as True means that, when an unrecognized object is encountered, that object will be deep-copied. To handle shared and cyclic-referencing objects, the deep_clone(...) function stores its own memo dictionary. When the control is given to the standard deepcopy(...) function, the memo dictionary of deep_clone(...) will be passed to deepcopy.	False
otherwise_return	bool	Setting this as True means that, when an unrecognized object is encountered, that object itself will be returned (i.e. will be a part of the created clone).	False
otherwise_fail	bool	Setting this as True means that, when an unrecognized object is encountered, a TypeError will be raised.	False
memo	Optional[dict]	Optionally a dictionary. In most scenarios, when this function is called from outside, this is expected to be left as None.	None

Returns:

Type	Description
Any	The newly made clone of the original object.

Source code in evotorch/tools/cloning.py

def deep_clone(  # noqa: C901
    x: Any,
    *,
    otherwise_deepcopy: bool = False,
    otherwise_return: bool = False,
    otherwise_fail: bool = False,
    memo: Optional[dict] = None,
) -> Any:
    """
    A recursive cloning function similar to the standard `deepcopy`.

    The difference between `deep_clone(...)` and `deepcopy(...)` is that
    `deep_clone(...)`, while recursively traversing, will run the `.clone()`
    method on the PyTorch tensors it encounters, so that the cloned tensors
    are forcefully detached from their storages (instead of cloning those
    storages as well).

    At the moment of writing this documentation, the current behavior of
    PyTorch tensors upon being deep-copied is to clone themselves AND their
    storages. Therefore, if a PyTorch tensor is a slice of a large tensor
    (which has a large storage), then the large storage will also be
    deep-copied, and the newly made clone of the tensor will point to a newly
    made large storage. One might instead prefer to clone tensors in such a
    way that the newly made tensor points to a newly made storage that
    contains just enough data for the tensor (with the unused data being
    dropped). When such a behavior is desired, one can use this
    `deep_clone(...)` function.

    Upon encountering a read-only and/or immutable data, this function will
    NOT modify the read-only behavior. For example, the deep-clone of a
    ReadOnlyTensor is still a ReadOnlyTensor, and the deep-clone of a
    read-only numpy array is still a read-only numpy array. Note that this
    behavior is different than the `clone()` method of a ReadOnlyTensor
    and the `copy()` method of a numpy array. The reason for this
    protective behavior is that since this is a deep-cloning operation,
    the encountered tensors and/or arrays might be the components of the root
    object, and changing their read-only attributes might affect the integrity
    of this root object.

    The `deep_clone(...)` function needs to know what to do when an object
    of unrecognized type is encountered. Therefore, the user is expected to
    set one of these arguments as True (and leave the others as False):
    `otherwise_deepcopy`, `otherwise_return`, `otherwise_fail`.

    Args:
        x: The object which will be deep-cloned. This object can be a standard
            Python container (i.e. list, tuple, dict, set), an instance of
            Problem, Solution, SolutionBatch, ObjectArray, ImmutableContainer,
            Clonable, and also any other type of object if either the argument
            `otherwise_deepcopy` or the argument `otherwise_return` is set as
            True.
        otherwise_deepcopy: Setting this as True means that, when an
            unrecognized object is encountered, that object will be
            deep-copied. To handle shared and cyclic-referencing objects,
            the `deep_clone(...)` function stores its own memo dictionary.
            When the control is given to the standard `deepcopy(...)`
            function, the memo dictionary of `deep_clone(...)` will be passed
            to `deepcopy`.
        otherwise_return: Setting this as True means that, when an
            unrecognized object is encountered, that object itself will be
            returned (i.e. will be a part of the created clone).
        otherwise_fail: Setting this as True means that, when an unrecognized
            object is encountered, a TypeError will be raised.
        memo: Optionally a dictionary. In most scenarios, when this function
            is called from outside, this is expected to be left as None.
    Returns:
        The newly made clone of the original object.
    """
    from .objectarray import ObjectArray
    from .readonlytensor import ReadOnlyTensor

    if memo is None:
        # If a memo dictionary was not given, make a new one now.
        memo = {}

    # Get the id of the object being cloned.
    x_id = id(x)

    if x_id in memo:
        # If the id of the object being cloned is already in the memo dictionary, then this object was previously
        # cloned. We just return that clone.
        return memo[x_id]

    # Count how many of the arguments `otherwise_deepcopy`, `otherwise_return`, and `otherwise_fail` was set as True.
    # In this context, we call these arguments as fallback behaviors.
    fallback_behaviors = (otherwise_deepcopy, otherwise_return, otherwise_fail)
    enabled_behavior_count = sum(1 for behavior in fallback_behaviors if behavior)

    if enabled_behavior_count == 0:
        # If none of the fallback behaviors was enabled, then we raise an error.
        raise ValueError(
            "The action to take with objects of unrecognized types is not known because"
            " none of these arguments was set as True: `otherwise_deepcopy`, `otherwise_return`, `otherwise_fail`."
            " Please set one of these arguments as True."
        )
    elif enabled_behavior_count == 1:
        # If one of the fallback behaviors was enabled, then we received our expected input. We do nothing here.
        pass
    else:
        # If the number of enabled fallback behaviors is an unexpected value. then we raise an error.
        raise ValueError(
            f"The following arguments were received, which is conflicting: otherwise_deepcopy={otherwise_deepcopy},"
            f" otherwise_return={otherwise_return}, otherwise_fail={otherwise_fail}."
            f" Please set exactly one of these arguments as True and leave the others as False."
        )

    # This inner function specifies how the deep_clone function should call itself.
    def call_self(obj: Any) -> Any:
        return deep_clone(
            obj,
            otherwise_deepcopy=otherwise_deepcopy,
            otherwise_return=otherwise_return,
            otherwise_fail=otherwise_fail,
            memo=memo,
        )

    # Below, we handle the cloning behaviors case by case.
    if (x is None) or (x is NotImplemented) or (x is Ellipsis):
        result = deepcopy(x)
    elif isinstance(x, (Number, str, bytes, bytearray)):
        result = deepcopy(x, memo=memo)
    elif isinstance(x, np.ndarray):
        result = x.copy()
        result.flags["WRITEABLE"] = x.flags["WRITEABLE"]
    elif isinstance(x, (ObjectArray, ReadOnlyClonable)):
        result = x.clone(preserve_read_only=True, memo=memo)
    elif isinstance(x, ReadOnlyTensor):
        result = x.clone(preserve_read_only=True)
    elif isinstance(x, torch.Tensor):
        result = x.clone()
    elif isinstance(x, Clonable):
        result = x.clone(memo=memo)
    elif isinstance(x, (dict, OrderedDict)):
        result = type(x)()
        memo[x_id] = result
        for k, v in x.items():
            result[call_self(k)] = call_self(v)
    elif isinstance(x, list):
        result = type(x)()
        memo[x_id] = result
        for item in x:
            result.append(call_self(item))
    elif isinstance(x, set):
        result = type(x)()
        memo[x_id] = result
        for item in x:
            result.add(call_self(item))
    elif isinstance(x, tuple):
        result = []
        memo[x_id] = result
        for item in x:
            result.append(call_self(item))
        if hasattr(x, "_fields"):
            result = type(x)(*result)
        else:
            result = type(x)(result)
        memo[x_id] = result
    else:
        # If the object is not recognized, we use the fallback behavior.
        if otherwise_deepcopy:
            result = deepcopy(x, memo=memo)
        elif otherwise_return:
            result = x
        elif otherwise_fail:
            raise TypeError(f"Do not know how to clone {repr(x)} (of type {type(x)}).")
        else:
            raise RuntimeError("The function `deep_clone` reached an unexpected state. This might be a bug.")

    if (x_id not in memo) and (result is not x):
        # If the newly made clone is still not in the memo dictionary AND the "clone" is not just a reference to the
        # original object, we make sure that it is in the memo dictionary.
        memo[x_id] = result

    # Finally, the result is returned.
    return result