tff.aggregators.MeanFactory

Aggregation factory for weighted mean.

Inherits From: WeightedAggregationFactory

tff.aggregators.MeanFactory(
    value_sum_factory: Optional[tff.aggregators.UnweightedAggregationFactory] = None,
    weight_sum_factory: Optional[tff.aggregators.UnweightedAggregationFactory] = None,
    no_nan_division: bool = False
)

Used in the notebooks

Used in the tutorials

The created tff.templates.AggregationProcess computes the weighted mean of values placed at CLIENTS, and outputs the mean placed at SERVER.

The input arguments of the next attribute of the process returned by create are <state, value, weight>, where weight is a scalar broadcasted to the structure of value, and the weighted mean refers to the expression sum(value * weight) / sum(weight).

The implementation is parameterized by two inner aggregation factories responsible for the summations above, with the following high-level steps.

  • Multiplication of value and weight at CLIENTS.
  • Delegation to inner value_sum_factory and weight_sum_factory to realize the sum of weighted values and weights.
  • Division of summed weighted values and summed weights at SERVER.

Note that the the division at SERVER can protect against division by 0, as specified by no_nan_division constructor argument.

The state is the composed state of the aggregation processes created by the two inner aggregation factories. The same holds for measurements.

value_sum_factory An optional tff.aggregators.UnweightedAggregationFactory responsible for summation of weighted values. If not specified, tff.aggregators.SumFactory is used.
weight_sum_factory An optional tff.aggregators.UnweightedAggregationFactory responsible for summation of weights. If not specified, tff.aggregators.SumFactory is used.
no_nan_division A bool. If True, the computed mean is 0 if sum of weights is equal to 0.

TypeError If provided value_sum_factory or weight_sum_factory is not an instance of tff.aggregators.UnweightedAggregationFactory.

Methods

create

View source

create(
    value_type: factory.ValueType, weight_type: factory.ValueType
) -> tff.templates.AggregationProcess

Creates a tff.aggregators.AggregationProcess with weights.

The provided value_type and weight_type are non-federated tff.Types. That is, neither is a tff.FederatedType.

The returned tff.aggregators.AggregationProcess will be created for aggregation of pairs of values matching value_type and weight_type placed at tff.CLIENTS. That is, its next method will expect type <S@SERVER, {value_type}@CLIENTS, {weight_type}@CLIENTS>, where S is the unplaced return type of its initialize method.

Args
value_type A non-federated tff.Type.
weight_type A non-federated tff.Type.

Returns
A tff.templates.AggregationProcess.