def sequence_map(self, fn, arg):
"""Implements `sequence_map` as defined in `api/intrinsics.py`."""
fn = value_impl.to_value(fn, None, self._context_stack)
py_typecheck.check_type(fn.type_signature, computation_types.FunctionType)
arg = value_impl.to_value(arg, None, self._context_stack)
if isinstance(arg.type_signature, computation_types.SequenceType):
fn = value_impl.ValueImpl.get_comp(fn)
arg = value_impl.ValueImpl.get_comp(arg)
return value_impl.ValueImpl(
building_block_factory.create_sequence_map(fn, arg),
self._context_stack)
elif isinstance(arg.type_signature, computation_types.FederatedType):
parameter_type = computation_types.SequenceType(
fn.type_signature.parameter)
result_type = computation_types.SequenceType(fn.type_signature.result)
intrinsic_type = computation_types.FunctionType(
(fn.type_signature, parameter_type), result_type)
intrinsic = building_blocks.Intrinsic(intrinsic_defs.SEQUENCE_MAP.uri,
intrinsic_type)
intrinsic_impl = value_impl.ValueImpl(intrinsic, self._context_stack)
local_fn = value_utils.get_curried(intrinsic_impl)(fn)
if arg.type_signature.placement in [
placements.SERVER, placements.CLIENTS
]:
return self.federated_map(local_fn, arg)
else:
raise TypeError('Unsupported placement {}.'.format(
arg.type_signature.placement))
else:
raise TypeError(
'Cannot apply `tff.sequence_map()` to a value of type {}.'.format(
arg.type_signature))
def sequence_map(fn, arg):
"""Maps a TFF sequence `value` pointwise using a given function `fn`.
This function supports two modes of usage:
* When applied to a non-federated sequence, it maps individual elements of
the sequence pointwise. If the supplied `fn` is of type `T->U` and
the sequence `arg` is of type `T*` (a sequence of `T`-typed elements),
the result is a sequence of type `U*` (a sequence of `U`-typed elements),
with each element of the input sequence individually mapped by `fn`.
In this mode of usage, `sequence_map` behaves like a compuatation with type
signature `<T->U,T*> -> U*`.
* When applied to a federated sequence, `sequence_map` behaves as if it were
individually applied to each member constituent. In this mode of usage, one
can think of `sequence_map` as a specialized variant of `federated_map` that
is designed to work with sequences and allows one to
specify a `fn` that operates at the level of individual elements.
Indeed, under the hood, when `sequence_map` is invoked on a federated type,
it injects `federated_map`, thus
emitting expressions like
`federated_map(a -> sequence_map(fn, x), arg)`.
Args:
fn: A mapping function to apply pointwise to elements of `arg`.
arg: A value of a TFF type that is either a sequence, or a federated
sequence.
Returns:
A sequence with the result of applying `fn` pointwise to each
element of `arg`, or if `arg` was federated, a federated sequence
with the result of invoking `sequence_map` on member sequences locally
and independently at each location.
Raises:
TypeError: If the arguments are not of the appropriate types.
"""
fn = value_impl.to_value(fn, None)
py_typecheck.check_type(fn.type_signature, computation_types.FunctionType)
arg = value_impl.to_value(arg, None)
if arg.type_signature.is_sequence():
comp = building_block_factory.create_sequence_map(fn.comp, arg.comp)
comp = _bind_comp_as_reference(comp)
return value_impl.Value(comp)
elif arg.type_signature.is_federated():
parameter_type = computation_types.SequenceType(
fn.type_signature.parameter)
result_type = computation_types.SequenceType(fn.type_signature.result)
intrinsic_type = computation_types.FunctionType(
(fn.type_signature, parameter_type), result_type)
intrinsic = building_blocks.Intrinsic(intrinsic_defs.SEQUENCE_MAP.uri,
intrinsic_type)
intrinsic_impl = value_impl.Value(intrinsic)
local_fn = value_utils.get_curried(intrinsic_impl)(fn)
return federated_map(local_fn, arg)
else:
raise TypeError(
'Cannot apply `tff.sequence_map()` to a value of type {}.'.format(
arg.type_signature))
def create_whimsy_called_sequence_map(parameter_name, parameter_type=tf.int32):
r"""Returns a whimsy called sequence map.
Call
/ \
sequence_map data
Args:
parameter_name: The name of the parameter.
parameter_type: The type of the parameter.
"""
fn = create_identity_function(parameter_name, parameter_type)
arg_type = computation_types.SequenceType(parameter_type)
arg = building_blocks.Data('data', arg_type)
return building_block_factory.create_sequence_map(fn, arg)
