tf.contrib.data.group_by_reducer( key_func, reducer )
A transformation that groups elements and performs a reduction.
This transformation maps element of a dataset to a key using
groups the elements by key. The
reducer is used to process each group; its
init_func is used to initialize state for each group when it is created, the
reduce_func is used to update the state every time an element is mapped to
the matching group, and the
finalize_func is used to map the final state to
an output value.
key_func: A function mapping a nested structure of tensors (having shapes and types defined by
self.output_types) to a scalar
reducer: An instance of
Reducer, which captures the reduction logic using the
Dataset transformation function, which can be passed to