def clone(output,
replace=None,
strict=True,
share_inputs=True,
copy_inputs=DEPRECATED_ARG):
"""
Function that allows replacing subgraphs of a computational graph.
It returns a copy of the initial subgraph with the corresponding
substitutions.
Parameters
----------
output : Theano Variables (or Theano expressions)
Theano expression that represents the computational graph.
replace : dict
Dictionary describing which subgraphs should be replaced by what.
share_inputs : bool
If True, use the same inputs (and shared variables) as the original
graph. If False, clone them. Note that cloned shared variables still
use the same underlying storage, so they will always have the same
value.
copy_inputs
Deprecated, use share_inputs.
"""
if copy_inputs is not DEPRECATED_ARG:
warnings.warn('In `clone()` function, the argument `copy_inputs` has been deprecated and renamed into `share_inputs`')
assert share_inputs # since we used `copy_inputs` we should have default value for `share_inputs`
share_inputs = copy_inputs
if isinstance(replace, dict):
items = list(replace.items())
elif isinstance(replace, (list, tuple)):
items = replace
elif replace is None:
items = []
else:
raise ValueError(("replace is neither a dictionary, list, "
"tuple or None ! The value provided is %s,"
"of type %s")%(str(replace), str(type(replace))))
tmp_replace = [(x, x.type()) for x, y in items]
new_replace = [(x, y) for ((_, x), (_, y)) in zip(tmp_replace,
items)]
_, _outs, _ = rebuild_collect_shared(output,
[],
tmp_replace,
[],
strict,
share_inputs)
# TODO Explain why we call it twice ?!
_, outs, _ = rebuild_collect_shared(_outs,
[],
new_replace,
[],
strict,
share_inputs)
return outs
def clone(output,
replace=None,
strict=True,
share_inputs=True,
copy_inputs=DEPRECATED_ARG):
"""
Function that allows replacing subgraphs of a computational
graph. It returns a copy of the initial subgraph with the corresponding
substitutions.
:type output: Theano Variables (or Theano expressions)
:param outputs: Theano expression that represents the computational
graph
:type replace: dict
:param replace: dictionary describing which subgraphs should be
replaced by what
:type share_inputs: bool
:param share_inputs: If True, use the same inputs (and shared variables)
as the original graph. If False, clone them. Note that cloned
shared variables still use the same underlying storage, so they
will always have the same value.
:param copy_inputs: deprecated, use share_inputs.
"""
if copy_inputs is not DEPRECATED_ARG:
warnings.warn('In `clone()` function, the argument `copy_inputs` has been deprecated and renamed into `share_inputs`')
assert share_inputs # since we used `copy_inputs` we should have default value for `share_inputs`
share_inputs = copy_inputs
if isinstance(replace, dict):
items = replace.items()
elif isinstance(replace, (list, tuple)):
items = replace
elif replace is None:
items = []
else:
raise ValueError(("replace is neither a dictionary, list, "
"tuple or None ! The value provided is %s,"
"of type %s")%(str(replace), str(type(replace))))
tmp_replace = [(x, x.type()) for x, y in items]
new_replace = [(x, y) for ((_, x), (_, y)) in zip(tmp_replace,
items)]
_, _outs, _ = rebuild_collect_shared(output,
[],
tmp_replace,
[],
strict,
share_inputs)
# TODO Explain why we call it twice ?!
_, outs, _ = rebuild_collect_shared(_outs,
[],
new_replace,
[],
strict,
share_inputs)
return outs
def clone(output,
replace=None,
strict=True,
copy_inputs=True):
"""
Function that allows replacing subgraphs of a computational
graph. It returns a copy of the initial subgraph with the corresponding
substitutions.
:type output: Theano Variables (or Theano expressions)
:param outputs: Theano expression that represents the computational
graph
:type replace: dict
:param replace: dictionary describing which subgraphs should be
replaced by what
:type copy_inputs: bool
:param copy_inputs: If True, use the same inputs (and shared variables)
as the original graph. If False, clone them. Note that cloned
shared variables still use the same underlying storage, so they
will always have the same value.
"""
if isinstance(replace, dict):
items = replace.items()
elif isinstance(replace, (list, tuple)):
items = replace
elif replace is None:
items = []
else:
raise ValueError(("replace is neither a dictionary, list, "
"tuple or None ! The value provided is %s,"
"of type %s")%(str(replace), str(type(replace))))
tmp_replace = [(x, x.type()) for x, y in items]
new_replace = [(x, y) for ((_, x), (_, y)) in zip(tmp_replace,
items)]
_, _outs, _ = rebuild_collect_shared(output,
[],
tmp_replace,
[],
strict,
copy_inputs)
_, outs, _ = rebuild_collect_shared(_outs,
[],
new_replace,
[],
strict,
copy_inputs)
return outs
def clone(output, replace=None, strict=True, share_inputs=True):
"""
Function that allows replacing subgraphs of a computational
graph. It returns a copy of the initial subgraph with the corresponding
substitutions.
:type output: Theano Variables (or Theano expressions)
:param outputs: Theano expression that represents the computational
graph
:type replace: dict
:param replace: dictionary describing which subgraphs should be
replaced by what
:type share_inputs: bool
:param share_inputs: If True, use the same inputs (and shared variables)
as the original graph. If False, clone them. Note that cloned
shared variables still use the same underlying storage, so they
will always have the same value.
"""
inps, outs, other_stuff = rebuild_collect_shared(output,
[],
replace,
[],
strict,
share_inputs)
return outs
def clone(output,
replace=None,
strict=True,
copy_inputs=True):
"""
Function that allows replacing subgraphs of a computational
graph. It returns a copy of the initial subgraph with the corresponding
substitutions.
:type output: Theano Variables (or Theano expressions)
:param outputs: Theano expression that represents the computational
graph
:type replace: dict
:param replace: dictionary describing which subgraphs should be
replaced by what
"""
inps, outs, other_stuff = rebuild_collect_shared(output,
[],
replace,
[],
strict,
copy_inputs
)
return outs
def clone(output, replace=None, strict=True, share_inputs=True, copy_inputs=DEPRECATED_ARG):
"""
Function that allows replacing subgraphs of a computational
graph. It returns a copy of the initial subgraph with the corresponding
substitutions.
:type output: Theano Variables (or Theano expressions)
:param outputs: Theano expression that represents the computational
graph
:type replace: dict
:param replace: dictionary describing which subgraphs should be
replaced by what
:type share_inputs: bool
:param share_inputs: If True, use the same inputs (and shared variables)
as the original graph. If False, clone them. Note that cloned
shared variables still use the same underlying storage, so they
will always have the same value.
"""
if copy_inputs is not DEPRECATED_ARG:
warnings.warn('In `clone()` function, the argument `copy_inputs` has been deprecated and renamed into `share_inputs`')
assert share_inputs # since we used `copy_inputs` we should have default value for `share_inputs`
share_inputs = copy_inputs
inps, outs, other_stuff = rebuild_collect_shared(output,
[],
replace,
[],
strict,
share_inputs)
return outs
def clone_optimized_graph(f):
maker_ins = [x for x in f.maker.env.inputs
if not isinstance(x, theano.tensor.sharedvar.SharedVariable)]
inps, outs, _ = rebuild_collect_shared(f.maker.env.outputs,
maker_ins,
copy_inputs_over=False)
ins = [x for x in inps
if not isinstance(x, theano.tensor.sharedvar.SharedVariable)]
return (ins, outs)
def clone(output, replace=None, strict=True, copy_inputs=True):
"""
Function that allows replacing subgraphs of a computational
graph. It returns a copy of the initial subgraph with the corresponding
substitutions.
:type output: Theano Variables (or Theano expressions)
:param outputs: Theano expression that represents the computational
graph
:type replace: dict
:param replace: dictionary describing which subgraphs should be
replaced by what
:type copy_inputs: bool
:param copy_inputs: If True, use the same inputs (and shared variables)
as the original graph. If False, clone them. Note that cloned
shared variables still use the same underlying storage, so they
will always have the same value.
"""
if isinstance(replace, dict):
items = replace.items()
elif isinstance(replace, (list, tuple)):
items = replace
elif replace is None:
items = []
else:
raise ValueError(("replace is neither a dictionary, list, "
"tuple or None ! The value provided is %s,"
"of type %s") % (str(replace), str(type(replace))))
tmp_replace = [(x, x.type()) for x, y in items]
new_replace = [(x, y) for ((_, x), (_, y)) in zip(tmp_replace, items)]
_, _outs, _ = rebuild_collect_shared(output, [], tmp_replace, [], strict,
copy_inputs)
_, outs, _ = rebuild_collect_shared(_outs, [], new_replace, [], strict,
copy_inputs)
return outs
def clone_optimized_graph(f):
maker_ins = [
x for x in f.maker.env.inputs
if not isinstance(x, theano.tensor.sharedvar.SharedVariable)
]
inps, outs, _ = rebuild_collect_shared(f.maker.env.outputs,
maker_ins,
copy_inputs_over=False)
ins = [
x for x in inps
if not isinstance(x, theano.tensor.sharedvar.SharedVariable)
]
return (ins, outs)
def clone(output, replace=None, strict=True, copy_inputs=True):
"""
Function that allows replacing subgraphs of a computational
graph. It returns a copy of the initial subgraph with the corresponding
substitutions.
:type output: Theano Variables (or Theano expressions)
:param outputs: Theano expression that represents the computational
graph
:type replace: dict
:param replace: dictionary describing which subgraphs should be
replaced by what
"""
inps, outs, other_stuff = rebuild_collect_shared(output, [], replace, [],
strict, copy_inputs)
return outs
def clone(output, replace=None, strict=True, share_inputs=True):
"""
Function that allows replacing subgraphs of a computational graph.
It returns a copy of the initial subgraph with the corresponding
substitutions.
Parameters
----------
output : Theano Variables (or Theano expressions)
Theano expression that represents the computational graph.
replace: dict
Dictionary describing which subgraphs should be replaced by what.
share_inputs : bool
If True, use the same inputs (and shared variables) as the original
graph. If False, clone them. Note that cloned shared variables still
use the same underlying storage, so they will always have the same
value.
"""
inps, outs, other_stuff = rebuild_collect_shared(output, [], replace, [],
strict, share_inputs)
return outs
def scan(fn,
sequences=None,
outputs_info=None,
non_sequences=None,
n_steps=None,
truncate_gradient=-1,
go_backwards=False,
mode=None,
name=None,
options=None,
profile=False):
"""
This function constructs and applies a Scan op to the provided
arguments.
:param fn:
``fn`` is a function that describes the operations involved in one
step of ``scan``. ``fn`` should construct variables describing the
output of one iteration step. It should expect as input theano
variables representing all the slices of the input sequences
and previous values of the outputs, as well as all other arguments
given to scan as ``non_sequences``. The order in which scan passes
these variables to ``fn`` is the following :
* all time slices of the first sequence
* all time slices of the second sequence
* ...
* all time slices of the last sequence
* all past slices of the first output
* all past slices of the second otuput
* ...
* all past slices of the last output
* all other arguments (the list given as `non_sequences` to
scan)
The order of the sequences is the same as the one in the list
`sequences` given to scan. The order of the outputs is the same
as the order of ``output_info``. For any sequence or output the
order of the time slices is the same as the one in which they have
been given as taps. For example if one writes the following :
.. code-block:: python
scan(fn, sequences = [ dict(input= Sequence1, taps = [-3,2,-1])
, Sequence2
, dict(input = Sequence3, taps = 3) ]
, outputs_info = [ dict(initial = Output1, taps = [-3,-5])
, dict(initial = Output2, taps = None)
, Output3 ]
, non_sequences = [ Argument1, Argument 2])
``fn`` should expect the following arguments in this given order:
#. ``Sequence1[t-3]``
#. ``Sequence1[t+2]``
#. ``Sequence1[t-1]``
#. ``Sequence2[t]``
#. ``Sequence3[t+3]``
#. ``Output1[t-3]``
#. ``Output1[t-5]``
#. ``Output3[t-1]``
#. ``Argument1``
#. ``Argument2``
The list of ``non_sequences`` can also contain shared variables
used in the function, though ``scan`` is able to figure those
out on its own so they can be skipped. For the clarity of the
code we recommand though to provide them to scan. To some extend
``scan`` can also figure out other ``non sequences`` (not shared)
even if not passed to scan (but used by `fn`). A simple example of
this would be :
.. code-block:: python
import theano.tensor as TT
W = TT.matrix()
W_2 = W**2
def f(x):
return TT.dot(x,W_2)
The function is expected to return two things. One is a list of
outputs ordered in the same order as ``outputs_info``, with the
difference that there should be only one output variable per
output initial state (even if no tap value is used). Secondly
`fn` should return an update dictionary (that tells how to
update any shared variable after each iteration step). The
dictionary can optionally be given as a list of tuples. There is
no constraint on the order of these two list, ``fn`` can return
either ``(outputs_list, update_dictionary)`` or
``(update_dictionary, outputs_list)`` or just one of the two (in
case the other is empty).
To use ``scan`` as a while loop, the user needs to change the
function ``fn`` such that also a stopping condition is returned.
To do so, he/she needs to wrap the condition in an ``until`` class.
The condition should be returned as a third element, for example:
.. code-block:: python
...
return [y1_t, y2_t], {x:x+1}, theano.scan_module.until(x < 50)
Note that a number of steps (considered in here as the maximum
number of steps ) is still required even though a condition is
passed (and it is used to allocate memory if needed). = {}):
:param sequences:
``sequences`` is the list of Theano variables or dictionaries
describing the sequences ``scan`` has to iterate over. If a
sequence is given as wrapped in a dictionary, then a set of optional
information can be provided about the sequence. The dictionary
should have the following keys:
* ``input`` (*mandatory*) -- Theano variable representing the
sequence.
* ``taps`` -- Temporal taps of the sequence required by ``fn``.
They are provided as a list of integers, where a value ``k``
impiles that at iteration step ``t`` scan will pass to ``fn``
the slice ``t+k``. Default value is ``[0]``
Any Theano variable in the list ``sequences`` is automatically
wrapped into a dictionary where ``taps`` is set to ``[0]``
:param outputs_info:
``outputs_info`` is the list of Theano variables or dictionaries
describing the initial state of the outputs computed
recurrently. When this initial states are given as dictionary
optional information can be provided about the output corresponding
to these initial states. The dictionary should have the following
keys:
* ``initial`` -- Theano variable that represents the initial
state of a given output. In case the output is not computed
recursively (think of a map) and does not require a initial
state this field can be skiped. Given that only the previous
time step of the output is used by ``fn`` the initial state
should have the same shape as the output. If multiple time
taps are used, the initial state should have one extra
dimension that should cover all the possible taps. For example
if we use ``-5``, ``-2`` and ``-1`` as past taps, at step 0,
``fn`` will require (by an abuse of notation) ``output[-5]``,
``output[-2]`` and ``output[-1]``. This will be given by
the initial state, which in this case should have the shape
(5,)+output.shape. If this variable containing the initial
state is called ``init_y`` then ``init_y[0]`` *corresponds to*
``output[-5]``. ``init_y[1]`` *correponds to* ``output[-4]``,
``init_y[2]`` corresponds to ``output[-3]``, ``init_y[3]``
coresponds to ``output[-2]``, ``init_y[4]`` corresponds to
``output[-1]``. While this order might seem strange, it comes
natural from splitting an array at a given point. Assume that
we have a array ``x``, and we choose ``k`` to be time step
``0``. Then our initial state would be ``x[:k]``, while the
output will be ``x[k:]``. Looking at this split, elements in
``x[:k]`` are ordered exactly like those in ``init_y``.
* ``taps`` -- Temporal taps of the output that will be pass to
``fn``. They are provided as a list of *negative* integers,
where a value ``k`` implies that at iteration step ``t`` scan
will pass to ``fn`` the slice ``t+k``.
``scan`` will follow this logic if partial information is given:
* If an output is not wrapped in a dictionary, ``scan`` will wrap
it in one assuming that you use only the last step of the output
(i.e. it makes your tap value list equal to [-1]).
* If you wrap an output in a dictionary and you do not provide any
taps but you provide an initial state it will assume that you are
using only a tap value of -1.
* If you wrap an output in a dictionary but you do not provide any
initial state, it assumes that you are not using any form of
taps.
* If you provide a ``None`` instead of a variable or a empty
dictionary ``scan`` assumes that you will not use any taps for
this output (like for example in case of a map)
If ``outputs_info`` is an empty list or None, ``scan`` assumes
that no tap is used for any of the outputs. If information is
provided just for a subset of the outputs an exception is
raised (because there is no convention on how scan should map
the provided information to the outputs of ``fn``)
:param non_sequences:
``non_sequences`` is the list of arguments that are passed to
``fn`` at each steps. One can opt to exclude variable
used in ``fn`` from this list as long as they are part of the
computational graph, though for clarity we encourage not to do so.
:param n_steps:
``n_steps`` is the number of steps to iterate given as an int
or Theano scalar. If any of the input sequences do not have
enough elements, scan will raise an error. If the *value is 0* the
outputs will have *0 rows*. If the value is negative, ``scan``
will run backwards in time. If the ``go_backwards`` flag is already
set and also ``n_steps`` is negative, ``scan`` will run forward
in time. If n stpes is not provided, ``scan`` will figure
out the amount of steps it should run given its input sequences.
:param truncate_gradient:
``truncate_gradient`` is the number of steps to use in truncated
BPTT. If you compute gradients through a scan op, they are
computed using backpropagation through time. By providing a
different value then -1, you choose to use truncated BPTT instead
of classical BPTT, where you go for only ``truncate_gradient``
number of steps back in time.
:param go_backwards:
``go_backwards`` is a flag indicating if ``scan`` should go
backwards through the sequences. If you think of each sequence
as indexed by time, making this flag True would mean that
``scan`` goes back in time, namely that for any sequence it
starts from the end and goes towards 0.
:param name:
When profiling ``scan``, it is crucial to provide a name for any
instance of ``scan``. The profiler will produce an overall
profile of your code as well as profiles for the computation of
one step of each instance of ``scan``. The ``name`` of the instance
appears in those profiles and can greatly help to disambiguate
information.
:param mode:
It is recommended to leave this argument to None, especially
when profiling ``scan`` (otherwise the results are not going to
be accurate). If you prefer the computations of one step of
``scan`` to be done differently then the entire function, you
can use this parameter to describe how the computations in this
loop are done (see ``theano.function`` for details about
possible values and their meaning).
:param profile:
Flag or string. If true, or different from the empty string, a
profile object will be created and attached to the inner graph of
scan. In case ``profile`` is True, the profile object will have the
name of the scan instance, otherwise it will have the passed string.
Profile object collect (and print) information only when running the
inner graph with the new cvm linker ( with default modes,
other linkers this argument is useless)
:rtype: tuple
:return: tuple of the form (outputs, updates); ``outputs`` is either a
Theano variable or a list of Theano variables representing the
outputs of ``scan`` (in the same order as in
``outputs_info``). ``updates`` is a subclass of dictionary
specifying the
update rules for all shared variables used in scan
This dictionary should be passed to ``theano.function`` when
you compile your function. The change compared to a normal
dictionary is that we validate that keys are SharedVariable
and addition of those dictionary are validated to be consistent.
"""
# Note : see the internal documentation of the scan op for naming
# conventions and all other details
if options is None:
options = {}
rvals = scan_utils.canonical_arguments(sequences,
outputs_info,
non_sequences,
go_backwards,
n_steps)
inputs, states_and_outputs_info, parameters, T = rvals
# If we provided a known number of steps ( before compilation)
# and if that number is 1 or -1, then we can skip the Scan Op,
# and just apply the inner function once
# To do that we check here to see the nature of n_steps
T_value = None
if isinstance(n_steps, (float, int)):
T_value = int(n_steps)
else:
try:
T_value = opt.get_constant_value(n_steps)
except (TypeError, AttributeError):
T_value = None
if T_value in (1, -1):
return one_step_scan(fn,
inputs,
states_and_outputs_info,
parameters,
truncate_gradient)
# 1. Variable representing the current time step
t = scalar_shared(numpy.int64(0), name='t')
# 2. Allocate memory for the states of scan.
mintaps = []
lengths = []
for pos, arg_info in enumerate(states_and_outputs_info):
if arg_info.get('taps', None) == [-1]:
mintaps.append(1)
lengths.append(scalar_shared(numpy.int64(0),
name='l%d' % pos))
arg_info['initial'] = scan_utils.expand(tensor.unbroadcast(
tensor.shape_padleft(arg_info['initial']), 0), T)
elif arg_info.get('taps', None):
if numpy.any(numpy.array(arg_info.get('taps', [])) > 0):
# Make sure we do not have requests for future values of a
# sequence we can not provide such values
raise ValueError('Can not use future taps of outputs',
arg_info)
mintap = abs(numpy.min(arg_info['taps']))
lengths.append(scalar_shared(numpy.int64(0),
name='l%d' % pos))
mintaps.append(mintap)
arg_info['initial'] = scan_utils.expand(
arg_info['initial'][:mintap], T)
else:
mintaps.append(0)
lengths.append(scalar_shared(numpy.int64(0),
name='l%d' % pos))
# 3. Generate arguments for the function passed to scan. This will
# function will return the outputs that need to be computed at every
# timesteps
inputs_slices = [input[t] for input in inputs]
states_slices = []
for n, state in enumerate(states_and_outputs_info):
# Check if it is actually a state and not an output
if mintaps[n] != 0:
for k in state['taps']:
states_slices.append(
state['initial'][(t + mintaps[n] + k) % lengths[n]])
# 4. Construct outputs that are to be computed by the inner
# function of scan
args = inputs_slices + states_slices + parameters
cond, states_and_outputs, updates = \
scan_utils.get_updates_and_outputs(fn(*args))
# User is allowed to provide no information if it only behaves like a
# map
if (len(states_and_outputs) != len(states_and_outputs_info) and
len(states_and_outputs_info) == 0):
mintaps = [0] * len(states_and_outputs)
# 5. Construct the scan op
# 5.1 Construct list of shared variables with updates (those that
# can be treated as states (i.e. of TensorType) and those that can not
# (like Random States)
if cond is not None:
_cond = [cond]
else:
_cond = []
rvals = rebuild_collect_shared(
states_and_outputs + _cond,
updates=updates,
rebuild_strict=True,
copy_inputs_over=True,
no_default_updates=False)
# extracting the arguments
input_variables, cloned_outputs, other_rval = rvals
clone_d, update_d, update_expr, shared_inputs = other_rval
additional_input_states = []
additional_output_states = []
additional_lengths = []
additional_mintaps = []
original_numeric_shared_variables = []
non_numeric_input_states = []
non_numeric_output_states = []
original_non_numeric_shared_variables = []
pos = len(lengths)
for sv in shared_inputs:
if sv in update_d:
if isinstance(sv, (TensorVariable, TensorSharedVariable)):
# We can treat it as a sit sot
nw_state = scan_utils.expand(
tensor.unbroadcast(tensor.shape_padleft(sv), 0), T)
additional_lengths.append(scalar_shared(numpy.int64(0),
name='l%d' % pos))
pos = pos + 1
additional_mintaps.append(1)
additional_input_states.append(nw_state)
additional_output_states.append(
scan_utils.clone(tensor.set_subtensor(
nw_state[(t + 1) % additional_lengths[-1]],
update_d[sv])))
original_numeric_shared_variables.append(sv)
else:
non_numeric_input_states.append(sv)
non_numeric_output_states.append(update_d[sv])
original_non_numeric_shared_variables.append(sv)
# Replace shared variables in the update
_additional_output_states = []
replace = {}
for sv, buf in zip(original_numeric_shared_variables,
additional_input_states):
replace[sv] = buf[t]
for out in additional_output_states:
_additional_output_states.append(
scan_utils.clone(out, replace=replace))
additional_output_states = _additional_output_states
# 5.2 Collect inputs/outputs of the inner function
inputs = []
outputs = []
for n, mintap in enumerate(mintaps):
if mintap != 0:
input_state = states_and_outputs_info[n]['initial']
inputs.append(input_state)
outputs.append(
tensor.set_subtensor(
input_state[(t + mintap) % lengths[n]],
states_and_outputs[n]))
else:
mem_buffer = scan_utils.allocate_memory(
T, states_and_outputs_info[n], states_and_outputs[n])
inputs.append(output)
outputs.append(
tensor.set_subtensor(output[t % lengths[n]],
states_and_outputs[n]))
inputs.extend(additional_input_states)
outputs.extend(additional_output_states)
lengths.extend(additional_lengths)
mintaps.extend(additional_mintaps)
inputs.extend(non_numeric_input_states)
outputs.extend(non_numeric_output_states)
all_other_inputs = gof.graph.inputs(outputs)
parameters = [x for x in all_other_inputs
if (x not in inputs and x not in lengths and x is not t
and isinstance(x, gof.Variable) and
not isinstance(x, gof.Constant))]
inputs.extend(parameters)
# 5.3 Construct the the options dictionary
options['name'] = name
options['profile'] = profile
options['mode'] = mode
options['inplace'] = False
options['gpu'] = False
options['truncate_gradient'] = truncate_gradient
options['hash_inner_graph'] = 0
# 5.4 Construct the ScanOp instance
local_op = scan_op.ScanOp(inputs=inputs,
outputs=outputs,
lengths=lengths,
switches=[],
mintaps=mintaps,
index=t,
options=options,
as_repeatUntil=cond)
# Note that we get here all the outputs followed by the update rules to
# the shared variables we had in our scan
# we know that we have (in this given order):
# * len(states_and_outputs) real outputs
# * len(additional_input_states) updates for numeric shared variable
# * len(non_numeric_input_states) updates for non numeric shared
# variables
scan_inputs = [T] + inputs
scan_outputs_update_rules = scan_utils.to_list(local_op(*scan_inputs))
# 5.5 Collect outputs and add permutation object
scan_outputs = []
for pos in xrange(len(states_and_outputs)):
out = scan_utils.ScanPermutation(mintaps[pos])(
scan_outputs_update_rules[pos], t)
scan_outputs.append(out[mintaps[pos]:])
# 5.6 Construct updates dictionary
update_rules = scan_outputs_update_rules[len(states_and_outputs):]
updates = {}
for v, u in izip(original_numeric_shared_variables,
update_rules[:len(additional_input_states)]):
updates[v] = u[-1]
for v, u in izip(original_non_numeric_shared_variables,
update_rules[len(additional_input_states):]):
updates[v] = u
# Step 5.7 We are done and can return everything back to the user
return scan_outputs, updates
def scan(fn,
sequences=None,
outputs_info=None,
non_sequences=None,
n_steps=None,
truncate_gradient=-1,
go_backwards=False,
mode=None,
name=None,
options=None,
profile=False):
"""
This function constructs and applies a Scan op to the provided
arguments.
:param fn:
``fn`` is a function that describes the operations involved in one
step of ``scan``. ``fn`` should construct variables describing the
output of one iteration step. It should expect as input theano
variables representing all the slices of the input sequences
and previous values of the outputs, as well as all other arguments
given to scan as ``non_sequences``. The order in which scan passes
these variables to ``fn`` is the following :
* all time slices of the first sequence
* all time slices of the second sequence
* ...
* all time slices of the last sequence
* all past slices of the first output
* all past slices of the second otuput
* ...
* all past slices of the last output
* all other arguments (the list given as `non_sequences` to
scan)
The order of the sequences is the same as the one in the list
`sequences` given to scan. The order of the outputs is the same
as the order of ``outputs_info``. For any sequence or output the
order of the time slices is the same as the one in which they have
been given as taps. For example if one writes the following :
.. code-block:: python
scan(fn, sequences = [ dict(input= Sequence1, taps = [-3,2,-1])
, Sequence2
, dict(input = Sequence3, taps = 3) ]
, outputs_info = [ dict(initial = Output1, taps = [-3,-5])
, dict(initial = Output2, taps = None)
, Output3 ]
, non_sequences = [ Argument1, Argument 2])
``fn`` should expect the following arguments in this given order:
#. ``Sequence1[t-3]``
#. ``Sequence1[t+2]``
#. ``Sequence1[t-1]``
#. ``Sequence2[t]``
#. ``Sequence3[t+3]``
#. ``Output1[t-3]``
#. ``Output1[t-5]``
#. ``Output3[t-1]``
#. ``Argument1``
#. ``Argument2``
The list of ``non_sequences`` can also contain shared variables
used in the function, though ``scan`` is able to figure those
out on its own so they can be skipped. For the clarity of the
code we recommend though to provide them to scan. To some extend
``scan`` can also figure out other ``non sequences`` (not shared)
even if not passed to scan (but used by `fn`). A simple example of
this would be :
.. code-block:: python
import theano.tensor as TT
W = TT.matrix()
W_2 = W**2
def f(x):
return TT.dot(x,W_2)
The function is expected to return two things. One is a list of
outputs ordered in the same order as ``outputs_info``, with the
difference that there should be only one output variable per
output initial state (even if no tap value is used). Secondly
`fn` should return an update dictionary (that tells how to
update any shared variable after each iteration step). The
dictionary can optionally be given as a list of tuples. There is
no constraint on the order of these two list, ``fn`` can return
either ``(outputs_list, update_dictionary)`` or
``(update_dictionary, outputs_list)`` or just one of the two (in
case the other is empty).
To use ``scan`` as a while loop, the user needs to change the
function ``fn`` such that also a stopping condition is returned.
To do so, he/she needs to wrap the condition in an ``until`` class.
The condition should be returned as a third element, for example:
.. code-block:: python
...
return [y1_t, y2_t], {x:x+1}, theano.scan_module.until(x < 50)
Note that a number of steps (considered in here as the maximum
number of steps ) is still required even though a condition is
passed (and it is used to allocate memory if needed). = {}):
:param sequences:
``sequences`` is the list of Theano variables or dictionaries
describing the sequences ``scan`` has to iterate over. If a
sequence is given as wrapped in a dictionary, then a set of optional
information can be provided about the sequence. The dictionary
should have the following keys:
* ``input`` (*mandatory*) -- Theano variable representing the
sequence.
* ``taps`` -- Temporal taps of the sequence required by ``fn``.
They are provided as a list of integers, where a value ``k``
impiles that at iteration step ``t`` scan will pass to ``fn``
the slice ``t+k``. Default value is ``[0]``
Any Theano variable in the list ``sequences`` is automatically
wrapped into a dictionary where ``taps`` is set to ``[0]``
:param outputs_info:
``outputs_info`` is the list of Theano variables or dictionaries
describing the initial state of the outputs computed
recurrently. When this initial states are given as dictionary
optional information can be provided about the output corresponding
to these initial states. The dictionary should have the following
keys:
* ``initial`` -- Theano variable that represents the initial
state of a given output. In case the output is not computed
recursively (think of a map) and does not require a initial
state this field can be skiped. Given that only the previous
time step of the output is used by ``fn`` the initial state
should have the same shape as the output. If multiple time
taps are used, the initial state should have one extra
dimension that should cover all the possible taps. For example
if we use ``-5``, ``-2`` and ``-1`` as past taps, at step 0,
``fn`` will require (by an abuse of notation) ``output[-5]``,
``output[-2]`` and ``output[-1]``. This will be given by
the initial state, which in this case should have the shape
(5,)+output.shape. If this variable containing the initial
state is called ``init_y`` then ``init_y[0]`` *corresponds to*
``output[-5]``. ``init_y[1]`` *correponds to* ``output[-4]``,
``init_y[2]`` corresponds to ``output[-3]``, ``init_y[3]``
coresponds to ``output[-2]``, ``init_y[4]`` corresponds to
``output[-1]``. While this order might seem strange, it comes
natural from splitting an array at a given point. Assume that
we have a array ``x``, and we choose ``k`` to be time step
``0``. Then our initial state would be ``x[:k]``, while the
output will be ``x[k:]``. Looking at this split, elements in
``x[:k]`` are ordered exactly like those in ``init_y``.
* ``taps`` -- Temporal taps of the output that will be pass to
``fn``. They are provided as a list of *negative* integers,
where a value ``k`` implies that at iteration step ``t`` scan
will pass to ``fn`` the slice ``t+k``.
``scan`` will follow this logic if partial information is given:
* If an output is not wrapped in a dictionary, ``scan`` will wrap
it in one assuming that you use only the last step of the output
(i.e. it makes your tap value list equal to [-1]).
* If you wrap an output in a dictionary and you do not provide any
taps but you provide an initial state it will assume that you are
using only a tap value of -1.
* If you wrap an output in a dictionary but you do not provide any
initial state, it assumes that you are not using any form of
taps.
* If you provide a ``None`` instead of a variable or a empty
dictionary ``scan`` assumes that you will not use any taps for
this output (like for example in case of a map)
If ``outputs_info`` is an empty list or None, ``scan`` assumes
that no tap is used for any of the outputs. If information is
provided just for a subset of the outputs an exception is
raised (because there is no convention on how scan should map
the provided information to the outputs of ``fn``)
:param non_sequences:
``non_sequences`` is the list of arguments that are passed to
``fn`` at each steps. One can opt to exclude variable
used in ``fn`` from this list as long as they are part of the
computational graph, though for clarity we encourage not to do so.
:param n_steps:
``n_steps`` is the number of steps to iterate given as an int
or Theano scalar. If any of the input sequences do not have
enough elements, scan will raise an error. If the *value is 0* the
outputs will have *0 rows*. If the value is negative, ``scan``
will run backwards in time. If the ``go_backwards`` flag is already
set and also ``n_steps`` is negative, ``scan`` will run forward
in time. If n stpes is not provided, ``scan`` will figure
out the amount of steps it should run given its input sequences.
:param truncate_gradient:
``truncate_gradient`` is the number of steps to use in truncated
BPTT. If you compute gradients through a scan op, they are
computed using backpropagation through time. By providing a
different value then -1, you choose to use truncated BPTT instead
of classical BPTT, where you go for only ``truncate_gradient``
number of steps back in time.
:param go_backwards:
``go_backwards`` is a flag indicating if ``scan`` should go
backwards through the sequences. If you think of each sequence
as indexed by time, making this flag True would mean that
``scan`` goes back in time, namely that for any sequence it
starts from the end and goes towards 0.
:param name:
When profiling ``scan``, it is crucial to provide a name for any
instance of ``scan``. The profiler will produce an overall
profile of your code as well as profiles for the computation of
one step of each instance of ``scan``. The ``name`` of the instance
appears in those profiles and can greatly help to disambiguate
information.
:param mode:
It is recommended to leave this argument to None, especially
when profiling ``scan`` (otherwise the results are not going to
be accurate). If you prefer the computations of one step of
``scan`` to be done differently then the entire function, you
can use this parameter to describe how the computations in this
loop are done (see ``theano.function`` for details about
possible values and their meaning).
:param profile:
Flag or string. If true, or different from the empty string, a
profile object will be created and attached to the inner graph of
scan. In case ``profile`` is True, the profile object will have the
name of the scan instance, otherwise it will have the passed string.
Profile object collect (and print) information only when running the
inner graph with the new cvm linker ( with default modes,
other linkers this argument is useless)
:rtype: tuple
:return: tuple of the form (outputs, updates); ``outputs`` is either a
Theano variable or a list of Theano variables representing the
outputs of ``scan`` (in the same order as in
``outputs_info``). ``updates`` is a subclass of dictionary
specifying the
update rules for all shared variables used in scan
This dictionary should be passed to ``theano.function`` when
you compile your function. The change compared to a normal
dictionary is that we validate that keys are SharedVariable
and addition of those dictionary are validated to be consistent.
"""
# Note : see the internal documentation of the scan op for naming
# conventions and all other details
if options is None:
options = {}
rvals = scan_utils.canonical_arguments(sequences,
outputs_info,
non_sequences,
go_backwards,
n_steps)
inputs, states_and_outputs_info, parameters, T = rvals
# If we provided a known number of steps ( before compilation)
# and if that number is 1 or -1, then we can skip the Scan Op,
# and just apply the inner function once
# To do that we check here to see the nature of n_steps
T_value = None
if isinstance(n_steps, (float, int)):
T_value = int(n_steps)
else:
try:
T_value = opt.get_scalar_constant_value(n_steps)
except (TypeError, AttributeError):
T_value = None
if T_value in (1, -1):
return one_step_scan(fn,
inputs,
states_and_outputs_info,
parameters,
truncate_gradient)
# 1. Variable representing the current time step
t = scalar_shared(numpy.int64(0), name='t')
# 2. Allocate memory for the states of scan.
mintaps = []
lengths = []
for pos, arg_info in enumerate(states_and_outputs_info):
if arg_info.get('taps', None) == [-1]:
mintaps.append(1)
lengths.append(scalar_shared(numpy.int64(0),
name='l%d' % pos))
arg_info['initial'] = scan_utils.expand(tensor.unbroadcast(
tensor.shape_padleft(arg_info['initial']), 0), T)
elif arg_info.get('taps', None):
if numpy.any(numpy.array(arg_info.get('taps', [])) > 0):
# Make sure we do not have requests for future values of a
# sequence we can not provide such values
raise ValueError('Can not use future taps of outputs',
arg_info)
mintap = abs(numpy.min(arg_info['taps']))
lengths.append(scalar_shared(numpy.int64(0),
name='l%d' % pos))
mintaps.append(mintap)
arg_info['initial'] = scan_utils.expand(
arg_info['initial'][:mintap], T)
else:
mintaps.append(0)
lengths.append(scalar_shared(numpy.int64(0),
name='l%d' % pos))
# 3. Generate arguments for the function passed to scan. This will
# function will return the outputs that need to be computed at every
# timesteps
inputs_slices = [input[t] for input in inputs]
states_slices = []
for n, state in enumerate(states_and_outputs_info):
# Check if it is actually a state and not an output
if mintaps[n] != 0:
for k in state['taps']:
states_slices.append(
state['initial'][(t + mintaps[n] + k) % lengths[n]])
# 4. Construct outputs that are to be computed by the inner
# function of scan
args = inputs_slices + states_slices + parameters
cond, states_and_outputs, updates = \
scan_utils.get_updates_and_outputs(fn(*args))
# User is allowed to provide no information if it only behaves like a
# map
if (len(states_and_outputs) != len(states_and_outputs_info) and
len(states_and_outputs_info) == 0):
mintaps = [0] * len(states_and_outputs)
# 5. Construct the scan op
# 5.1 Construct list of shared variables with updates (those that
# can be treated as states (i.e. of TensorType) and those that can not
# (like Random States)
if cond is not None:
_cond = [cond]
else:
_cond = []
rvals = rebuild_collect_shared(
states_and_outputs + _cond,
updates=updates,
rebuild_strict=True,
copy_inputs_over=True,
no_default_updates=False)
# extracting the arguments
input_variables, cloned_outputs, other_rval = rvals
clone_d, update_d, update_expr, shared_inputs = other_rval
additional_input_states = []
additional_output_states = []
additional_lengths = []
additional_mintaps = []
original_numeric_shared_variables = []
non_numeric_input_states = []
non_numeric_output_states = []
original_non_numeric_shared_variables = []
pos = len(lengths)
for sv in shared_inputs:
if sv in update_d:
if isinstance(sv, (TensorVariable, TensorSharedVariable)):
# We can treat it as a sit sot
nw_state = scan_utils.expand(
tensor.unbroadcast(tensor.shape_padleft(sv), 0), T)
additional_lengths.append(scalar_shared(numpy.int64(0),
name='l%d' % pos))
pos = pos + 1
additional_mintaps.append(1)
additional_input_states.append(nw_state)
additional_output_states.append(
scan_utils.clone(tensor.set_subtensor(
nw_state[(t + 1) % additional_lengths[-1]],
update_d[sv])))
original_numeric_shared_variables.append(sv)
else:
non_numeric_input_states.append(sv)
non_numeric_output_states.append(update_d[sv])
original_non_numeric_shared_variables.append(sv)
# Replace shared variables in the update
_additional_output_states = []
replace = {}
for sv, buf in zip(original_numeric_shared_variables,
additional_input_states):
replace[sv] = buf[t]
for out in additional_output_states:
_additional_output_states.append(
scan_utils.clone(out, replace=replace))
additional_output_states = _additional_output_states
# 5.2 Collect inputs/outputs of the inner function
inputs = []
outputs = []
for n, mintap in enumerate(mintaps):
if mintap != 0:
input_state = states_and_outputs_info[n]['initial']
inputs.append(input_state)
outputs.append(
tensor.set_subtensor(
input_state[(t + mintap) % lengths[n]],
states_and_outputs[n]))
else:
mem_buffer = scan_utils.allocate_memory(
T, states_and_outputs_info[n], states_and_outputs[n])
inputs.append(output)
outputs.append(
tensor.set_subtensor(output[t % lengths[n]],
states_and_outputs[n]))
inputs.extend(additional_input_states)
outputs.extend(additional_output_states)
lengths.extend(additional_lengths)
mintaps.extend(additional_mintaps)
inputs.extend(non_numeric_input_states)
outputs.extend(non_numeric_output_states)
all_other_inputs = gof.graph.inputs(outputs)
parameters = [x for x in all_other_inputs
if (x not in inputs and x not in lengths and x is not t
and isinstance(x, gof.Variable) and
not isinstance(x, gof.Constant))]
inputs.extend(parameters)
# 5.3 Construct the the options dictionary
options['name'] = name
options['profile'] = profile
options['mode'] = mode
options['inplace'] = False
options['gpu'] = False
options['truncate_gradient'] = truncate_gradient
options['hash_inner_graph'] = 0
# 5.4 Construct the ScanOp instance
local_op = scan_op.ScanOp(inputs=inputs,
outputs=outputs,
lengths=lengths,
switches=[],
mintaps=mintaps,
index=t,
options=options,
as_repeatUntil=cond)
# Note that we get here all the outputs followed by the update rules to
# the shared variables we had in our scan
# we know that we have (in this given order):
# * len(states_and_outputs) real outputs
# * len(additional_input_states) updates for numeric shared variable
# * len(non_numeric_input_states) updates for non numeric shared
# variables
scan_inputs = [T] + inputs
scan_outputs_update_rules = scan_utils.to_list(local_op(*scan_inputs))
# 5.5 Collect outputs and add permutation object
scan_outputs = []
for pos in xrange(len(states_and_outputs)):
out = scan_utils.ScanPermutation(mintaps[pos])(
scan_outputs_update_rules[pos], t)
scan_outputs.append(out[mintaps[pos]:])
# 5.6 Construct updates dictionary
update_rules = scan_outputs_update_rules[len(states_and_outputs):]
updates = {}
for v, u in izip(original_numeric_shared_variables,
update_rules[:len(additional_input_states)]):
updates[v] = u[-1]
for v, u in izip(original_non_numeric_shared_variables,
update_rules[len(additional_input_states):]):
updates[v] = u
# Step 5.7 We are done and can return everything back to the user
return scan_outputs, updates
def __init__(
self,
inputs,
outputs,
inline=False,
lop_overrides="default",
grad_overrides="default",
rop_overrides="default",
connection_pattern=None,
name=None,
**kwargs,
):
if not isinstance(outputs, list):
raise TypeError("outputs must be list, got %s" % type(outputs))
for i in inputs + outputs:
if not isinstance(i, gof.Variable):
raise TypeError(
"inputs and outputs must be Variable instances", i)
if "updates" in kwargs or "givens" in kwargs:
raise TypeError("updates and givens are not allowed here")
self.is_inline = inline
# To correctly support shared variables the inner fct should
# not see them. Otherwise there is a problem with the gradient.
self.shared_inputs = [
var for var in gof.graph.inputs(outputs)
if isinstance(var, SharedVariable)
]
shared_vars = [var.type() for var in self.shared_inputs]
new = rebuild_collect_shared(
outputs,
inputs=inputs + shared_vars,
replace=dict(zip(self.shared_inputs, shared_vars)),
copy_inputs_over=False,
)
(
local_inputs,
local_outputs,
[clone_d, update_d, update_expr, shared_inputs],
) = new
assert len(local_inputs) == len(inputs) + len(self.shared_inputs)
assert len(local_outputs) == len(outputs)
assert not update_d
assert not update_expr
assert not shared_inputs
self.local_inputs = local_inputs
self.local_outputs = local_outputs
self.inputs = inputs
self.outputs = outputs
self.kwargs = kwargs
self.input_types = [inp.type for inp in inputs]
self.output_types = [out.type for out in outputs]
if lop_overrides != "default":
if grad_overrides != "default":
raise ValueError(
"lop_overrides and grad_overrides are mutually exclusive")
else:
self.set_lop_overrides(lop_overrides)
self._lop_type = "lop"
elif grad_overrides != "default":
self.set_lop_overrides(grad_overrides)
self._lop_type = "grad"
else:
self.set_lop_overrides("default")
self._lop_type = "lop"
self.set_rop_overrides(rop_overrides)
self._connection_pattern = connection_pattern
if name is not None:
assert isinstance(name, str), "name must be None or string object"
self.name = name
def __init__(self, updated_vars, givens=None):
"""
updated_vars: sequence of (dst, expr) pairs
vals_memo: dict Variable -> [value]
"""
# -- unique_outputs is used here to ensure that there is some
# double-buffering going on, because actually dests and outputs can
# include some of the same variables (e.g. swap values)
dests, outputs = zip(*updated_vars)
#unique_outputs = map(deep_copy_op, outputs)
unique_outputs = outputs
# -- partial graph clone to use givens
stuff = rebuild_collect_shared(
unique_outputs,
inputs=list(dests) + [],
replace=givens,
rebuild_strict=True,
copy_inputs_over=True)
_inputs, unique_outputs_w_giv, other_stuff = stuff
clone_equiv1, _update_d, _update_expr, _shared_inputs = other_stuff
all_inputs = theano.gof.graph.inputs(unique_outputs_w_giv + _inputs)
# -- full graph clone to protect original graph
clone_equiv = {} # -- do not need order here
theano.gof.graph.clone_get_equiv(
[],
unique_outputs_w_giv + _inputs,
copy_inputs_and_orphans=True,
memo=clone_equiv)
# -- redirect through the second clone
for orig_var in clone_equiv1:
tmp = clone_equiv1[orig_var]
if tmp in clone_equiv:
clone_equiv[orig_var] = clone_equiv[tmp]
self.cloned_inputs = [clone_equiv[var] for var in all_inputs]
self.cloned_dests = [clone_equiv[var] for var in dests]
self.cloned_outputs = [clone_equiv[var] for var in unique_outputs_w_giv]
fgraph = theano.gof.fg.FunctionGraph(
self.cloned_inputs,
self.cloned_outputs)
# -- load up fgraph with features necessary to maintain correctness:
for node in fgraph.apply_nodes:
if getattr(node.op, 'destroy_map', None):
if not accept_inplace:
raise TypeError("Graph must not contain inplace operations",
node, node.op)
else:
fgraph.attach_feature(theano.gof.DestroyHandler())
break
# We need to protect all immutable inputs from inplace operations.
fgraph.attach_feature(
theano.compile.function_module.Supervisor(invar
for invar in self.cloned_inputs
if not ((invar in self.cloned_dests) or
(hasattr(fgraph, 'destroyers') and
fgraph.destroyers(input)))))
# If named nodes are replaced, keep the name
for feature in theano.compile.function_module.std_fgraph.features:
fgraph.attach_feature(feature())
fgraph.attach_feature(theano.tensor.opt.ShapeFeature())
# -- pre-install the shape information from the Hints created by
# e.g. SharedStorageWorkspace
done = {} # -- no order ok
for node in fgraph.toposort():
if is_hint_node(node):
if node.inputs[0] in done: continue
hints = OrderedDict(node.op.hints)
if 'shape' in hints:
x = node.inputs[0]
assert x.ndim == len(hints['shape'])
if x in done:
assert done[x] == hints['shape']
else:
var_shape = tuple(
map(theano.tensor.as_tensor_variable,
hints['shape']))
fgraph.shape_feature.shape_of[node.inputs[0]] = var_shape
done[x] = hints['shape']
self.updated_vars = updated_vars
self.all_inputs = all_inputs
self.outputs = outputs
self.unique_outputs = unique_outputs
self.clone_equiv = clone_equiv
self.fgraph = fgraph
