Source code for zfit.util.cache

"""Module for caching.


The basic concept of caching in Zfit builds on a "cacher", that caches a certain value and that
is dependent of "cache_dependents". By implementing `ZfitCachable`, an object will be able to play both
roles. And most importantly, it has a `_cache` dict, that contains all the cache.

Basic principle
===============

A "cacher" adds any dependents that it may comes across with `add_cache_dependents`. For example,
for a loss this would be all pdfs and data. Since :py:class:`~zfit.Space` is immutable, there is no need to add this
as a dependent. This leads to the "cache_dependent" to register the "cacher" and to remember it.

In case, any "cache_dependent" changes in a way the cache of itself (and any "cacher") is invalid,
which is done in the simplest case by decorating a method with `@invalidates_cache`, the "cache_dependent":

 * clears it's own cache with `reset_cache_self` and
 * "clears" any "cacher"s cache with `reset_cache(reseter=self)`, telling the "cacher" that it should
   reset the cache. This is also where more fine-grained control (depending on which "cache_dependent"
   calls `reset_cache`) can be brought into play.

Example with a pdf that caches the normalization:

.. code:: python

    class Parameter(Cachable):
        def load(new_value):  # does not require to build a new graph
            # do something

        @invalidates_cache
        def change_limits(new_limits):  # requires to build a new graph (as an example)
            # do something

    # create param1, param2 from `Parameter`

    class MyPDF(Cachable):
        def __init__(self, param1, param2):
            self.add_cache_dependents([param1, param2])

        def cached_func(...):
            if self._cache.get('my_name') is None:
                result = ...  # calculations here
                self._cache['my_name']
            else:
                result = self._cache['my_name']
            return result


"""

#  Copyright (c) 2020 zfit

import functools
import weakref
from abc import abstractmethod
from typing import Iterable, Union, Mapping

import numpy as np
import tensorflow as tf

from . import ztyping
from .container import convert_to_container
from ..core.interfaces import ZfitData, ZfitParameter, ZfitSpace


[docs]class ZfitCachable:
[docs] @abstractmethod def register_cacher(self, cacher: "ZfitCachable"): raise NotImplementedError
[docs] @abstractmethod def add_cache_dependents(self, cache_dependents, allow_non_cachable): """Add dependents that render the cache invalid if they change. Args: cache_dependents (ZfitCachable): allow_non_cachable (bool): If `True`, allow `cache_dependents` to be non-cachables. If `False`, any `cache_dependents` that is not a `ZfitCachable` will raise an error. Raises: TypeError: if one of the `cache_dependents` is not a `ZfitCachable` _and_ `allow_non_cachable` if `False`. """ pass
[docs] @abstractmethod def reset_cache_self(self): """Clear the cache of self and all dependent cachers.""" pass
[docs] @abstractmethod def reset_cache(self, reseter): pass
[docs]class Cachable(ZfitCachable): graph_caching_methods = [] instances = weakref.WeakSet() def __init__(self, *args, **kwargs): self._cache = {} self._cachers = weakref.WeakKeyDictionary() self.reset_cache_self() self.instances.add(self) super().__init__(*args, **kwargs) def __init_subclass__(cls) -> None: super().__init_subclass__() graph_caching_methods = [] for func_name in dir(cls): if not func_name.startswith("__"): func = getattr(cls, func_name) if callable(func) and hasattr(func, 'zfit_graph_cache_registered'): # assert hasattr(func, "_descriptor_cache"), "TensorFlow internals have changed. Need to update cache" func.zfit_graph_cache_registered = True graph_caching_methods.append(func) cls.graph_caching_methods = graph_caching_methods
[docs] def register_cacher(self, cacher: ztyping.CacherOrCachersType): """Register a `cacher` that caches values produces by this instance; a dependent. Args: cacher (): """ if not isinstance(cacher, ZfitCachable): raise TypeError("`cacher` is not a `ZfitCachable` but {}".format(type(cacher))) if not cacher in self._cachers: self._cachers[cacher] = None # could we have a more useful value?
[docs] def add_cache_dependents(self, cache_dependents: ztyping.CacherOrCachersType, allow_non_cachable: bool = True): """Add dependents that render the cache invalid if they change. Args: cache_dependents (ZfitCachable): allow_non_cachable (bool): If `True`, allow `cache_dependents` to be non-cachables. If `False`, any `cache_dependents` that is not a `ZfitCachable` will raise an error. Raises: TypeError: if one of the `cache_dependents` is not a `ZfitCachable` _and_ `allow_non_cachable` if `False`. """ cache_dependents = convert_to_container(cache_dependents) for cache_dependent in cache_dependents: if isinstance(cache_dependent, ZfitCachable): cache_dependent.register_cacher(self) elif not allow_non_cachable: raise TypeError("cache_dependent {} is not a `ZfitCachable` but {}".format(cache_dependent, type(cache_dependent)))
[docs] def reset_cache_self(self): """Clear the cache of self and all dependent cachers.""" self._clean_cache() self._inform_cachers()
[docs] def reset_cache(self, reseter: 'ZfitCachable'): self.reset_cache_self()
def _clean_cache(self): # for func_holder in self.graph_caching_methods: # func_holder.reset self._cache = {} return def _inform_cachers(self): for cacher in self._cachers: cacher.reset_cache(reseter=self)
[docs]def invalidate_graph(func): @functools.wraps(func) def wrapped_func(*args, **kwargs): self = args[0] if not isinstance(self, ZfitCachable): raise TypeError("Decorator can only be used in a subclass of `ZfitCachable`") self.reset_cache(reseter=self) return func(*args, **kwargs) return wrapped_func
[docs]class FunctionCacheHolder(Cachable): IS_TENSOR = object() def __init__(self, func, wrapped_func, cachables: Union[ZfitCachable, object, Iterable[Union[ZfitCachable, object]]] = None, cachables_mapping=None): """`tf.function` decorated function holder with caching dependencies on inputs. A `tf.function` creates a new graph for every signature that is encountered. It automatically caches them but thereby assumes that Python objects are immutable. Any mutation won't be detected. Therefore, an extra wrapper is needed. The input signature is compared with firstly checking whether the function is the same and then doing an equal comparison of the arguments (maybe too costly?). The `FunctionCacheHolder` holds the - original python function which serves as the hash of the object - wrapped python function, `wrapped_func` - the (keyword-)arguments If any of the keyword arguments changes in a way that the graph cache is invalid, this holder will have `is_valid` set to False and the `wrapped_func` cannot be used anymore, instead a new `tf.function` should be created as a call to the `wrapped_func` with the given arguments will result in an outdated graph. Args: func (function): Python function that serves as a hash of the holder. Notice that equality is different defined. wrapped_func (tf.function wrapped): Wrapped `func` with `tf.function`. The holder signals via `is_valid` whether this function is still valid to be used. cachables: objects that are cached. If they change, the cache is invalidated cachables_mapping (Mapping): keyword arguments to the function. If the values change, the cache is invalidated. """ # cache = {} if cache is None else cache self.delete_from_cache = False self.wrapped_func = wrapped_func # self.parent_cache = cache self.python_func = func self._hash_value = hash(self.python_func) if cachables is None and cachables_mapping is None: raise ValueError("Both `cachables and `cachables_mapping` are None. One needs to be different from None.") if cachables is None: cachables = [] if cachables_mapping is None: cachables_mapping = {} cachables = convert_to_container(cachables, container=list) cachables_values = convert_to_container(cachables_mapping.values(), container=list) cachables_all = cachables + cachables_values self.immutable_representation = self.create_immutable(cachables, cachables_mapping) # self._hash_value = hash(self.immutable_representation) super().__init__() # resets the cache self.add_cache_dependents(cachables_all) self.is_valid = True # needed to make the cache valid again
[docs] def reset_cache_self(self): self.is_valid = False
[docs] def create_immutable(self, args, kwargs): """Create a tuple of the args and kwargs by combining them as args + kwargs.keys() + kwargs.values()` Args: args: list like kwargs: dict-like Returns: tuple """ args = list(args) kwargs = list(kwargs.keys()) + list(kwargs.values()) combined = [] if args != []: combined += args if kwargs != []: combined += args combined_cleaned = [] for obj in combined: if isinstance(obj, ZfitData): obj = (id(obj),) elif isinstance(obj, ZfitParameter): obj = (ZfitParameter, obj.name) elif isinstance(obj, ZfitSpace): obj = (id(obj),) elif tf.is_tensor(obj): obj = self.IS_TENSOR elif isinstance(obj, np.ndarray): obj = (obj,) if sum(obj.shape) < 20 else id(obj) combined_cleaned.append(obj) return tuple(combined_cleaned)
def __hash__(self) -> int: return self._hash_value def __eq__(self, other: object) -> bool: if not isinstance(other, FunctionCacheHolder): return False # return all(obj1 == obj2 for obj1, obj2 in zip(self.immutable_representation, other.immutable_representation)) try: return all(np.equal(self.immutable_representation, other.immutable_representation)) except ValueError: # broadcasting does not work return False except TypeError: # OperatorNotAllowedError inherits from this return False # TODO: activate the below? costly, but runs? # except OperatorNotAllowedInGraphError: # we have to assume they're not the same # return False def __repr__(self) -> str: return f"<FunctionCacheHolder: {self.python_func}, valid={self.is_valid}>"
[docs]def clear_graph_cache(): from zfit.z.zextension import FunctionWrapperRegistry for registry in FunctionWrapperRegistry.registries: for all_meth in registry.function_cache.values(): for wrapped_meth in all_meth: wrapped_meth = wrapped_meth.wrapped_func wrapped_meth._created_variables = None wrapped_meth._stateful_fn = None wrapped_meth._stateless_fn = None wrapped_meth._descriptor_cache.clear() for registry in FunctionWrapperRegistry.registries: registry.reset() for instance in Cachable.instances: instance.reset_cache('global')
# Cachable.graph_caching_methods.clear()