The framework stacks multiple layers together when estimating a data set of properties.
Each layer will in turn attempt to evaluate the properties being estimated using the specific approach the layer represents, such as by running a set of simulations. If the layer is unable to estimate a given property, for example if a layer does not yet support a given property, or if the layer has insufficient data to reprocesses, the property will be passed to the next layer for it to try and evaluate.
In practice, this allows the framework to attempt to estimate a data set using the most rapid calculation layer first, before moving to successively slower yet more robust layers, and thus enabling as efficient as possible property estimation.
A calculation layer is defined by two objects - a
CalculationLayer object which implements the main layer
logic, and a
CalculationLayerSchema which defines those settings and options exposed required by the layer.
CalculationLayerSchema will be provided to the for each type of property that the layer is being asked to
estimate. The base
CalculationLayerSchema currently only exposes options for optionally defining either the
relative or absolute uncertainty that the layer should attempt to estimate the associated property type to within,
however custom schemas can be defined per layer.
The structure of a
CalculationLayer is relatively simple and permissive:
@calculation_layer() class MyCalculationLayer(CalculationLayer): @classmethod def required_schema_type(cls): return CalculationLayerSchema @classmethod def _schedule_calculation( cls, calculation_backend, storage_backend, layer_directory, batch ): ...
The first thing to note is the
calculation_layer() decorator which is being applied to the class. This registers
the calculation layer with the frameworks plug-in system, allowing it to be used in future calculations.
The only other requirements is that the class implement a
required_schema_type class method, which returns the
CalculationLayerSchema that is associated with this layer, and a
_schedule_calculation() is responsible for performing the actual property calculations.
The form of the
_schedule_calculation() function is very flexible:
@classmethod def _schedule_calculation( cls, calculation_backend, storage_backend, layer_directory, batch ): futures =  for queued_property in batch.queued_properties: futures.append( calculation_backend.submit_task( cls.process_property, queued_property, cls.__name__ ) ) return futures
It takes as arguments:
a CalculationBackend which is used to asynchronously distribute any calculations across the available compute resources.
a StorageBackend which may be used to store / cache any data generated by the calculations.
the path to the directory within which all of the calculation working files should be stored.
and must return a list of
Future objects (which either must be or implement the same API as the asyncio
Future object). The easiest way to generate the futures
is to perform any calculations using the
calculation_backend which will automatically return the
results of any functions as such.
The future objects returned by
_schedule_calculation() must return a
CalculationLayerResult object, which
the estimated property if the calculation was successful (or
a list of any exceptions (of type
EvaluatorException) which were raised during the calculation.
a list of any data to be stored by the storage backend.
As a minimal example of a method which returns one such object:
@classmethod def process_property(cls, physical_property, **_): """Return a result as if the property had been successfully estimated. """ # TODO: Do some calculations # Set the property provenance physical_property.source = CalculationSource(fidelity=cls.__name__) # Return the results object. results = CalculationLayerResult() results.physical_property = physical_property return results
Default schemas for each pair of a calculation layer and a type of physical property may be registered using the
# Register the default schema to use for density measurements being estimated # by the direct simulation calculation layer. register_calculation_schema( property_class=Density, layer_class=SimulationLayer, schema=Density.default_simulation_schema )
A list of the registered schemas is provided by the
registered_calculation_schemas module attribute.