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scan_views.py
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/
scan_views.py
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"""
This module provides syntax shortcut for the Scan Op.
See scan.py for details on scan.
"""
from __future__ import absolute_import, print_function, division
__docformat__ = 'restructedtext en'
__authors__ = ("Razvan Pascanu "
"Frederic Bastien "
"James Bergstra "
"Pascal Lamblin ")
__copyright__ = "(c) 2010, Universite de Montreal"
__contact__ = "Razvan Pascanu <r.pascanu@gmail>"
import logging
from theano.scan_module import scan
# Logging function for sending warning or info
_logger = logging.getLogger('theano.scan_module.scan_views')
################ Declaration of Views for Scan #######################
# The ``map`` view of Scan Op.
def map(fn,
sequences,
non_sequences=None,
truncate_gradient=-1,
go_backwards=False,
mode=None,
name=None):
"""
Similar behaviour as python's map.
Parameters
----------
fn
The function that ``map`` applies at each iteration step
(see ``scan`` for more info).
sequences
List of sequences over which ``map`` iterates
(see ``scan`` for more info).
non_sequences
List of arguments passed to ``fn``. ``map`` will not iterate over
these arguments (see ``scan`` for more info).
truncate_gradient
See ``scan``.
go_backwards : bool
Decides the direction of iteration. True means that sequences are parsed
from the end towards the beginning, while False is the other way around.
mode
See ``scan``.
name
See ``scan``.
"""
return scan(fn=fn,
sequences=sequences,
outputs_info=[],
non_sequences=non_sequences,
truncate_gradient=truncate_gradient,
go_backwards=go_backwards,
mode=mode,
name=name)
# The ``reduce`` view of Scan Op.
def reduce(fn,
sequences,
outputs_info,
non_sequences=None,
go_backwards=False,
mode=None,
name=None):
"""
Similar behaviour as python's reduce.
Parameters
----------
fn
The function that ``reduce`` applies at each iteration step
(see ``scan`` for more info).
sequences
List of sequences over which ``reduce`` iterates
(see ``scan`` for more info).
outputs_info
List of dictionaries describing the outputs of
reduce (see ``scan`` for more info).
non_sequences
List of arguments passed to ``fn``. ``reduce`` will
not iterate over these arguments (see ``scan`` for
more info).
go_backwards : bool
Decides the direction of iteration. True means that sequences are parsed
from the end towards the beginning, while False is the other way around.
mode
See ``scan``.
name
See ``scan``.
"""
rval = scan(fn=fn,
sequences=sequences,
outputs_info=outputs_info,
non_sequences=non_sequences,
go_backwards=go_backwards,
truncate_gradient=-1,
mode=mode,
name=name)
if isinstance(rval[0], (list, tuple)):
return [x[-1] for x in rval[0]], rval[1]
else:
return rval[0][-1], rval[1]
# The ``foldl`` view of Scan Op.
def foldl(fn,
sequences,
outputs_info,
non_sequences=None,
mode=None,
name=None):
"""
Similar behaviour as haskell's foldl.
Parameters
----------
fn
The function that ``foldl`` applies at each iteration step
(see ``scan`` for more info).
sequences
List of sequences over which ``foldl`` iterates
(see ``scan`` for more info).
outputs_info
List of dictionaries describing the outputs of reduce
(see ``scan`` for more info).
non_sequences
List of arguments passed to `fn`. ``foldl`` will not iterate over
these arguments (see ``scan`` for more info).
mode
See ``scan``.
name
See ``scan``.
"""
return reduce(fn=fn,
sequences=sequences,
outputs_info=outputs_info,
non_sequences=non_sequences,
go_backwards=False,
mode=mode,
name=name)
# The ``foldl`` view of Scan Op.
def foldr(fn,
sequences,
outputs_info,
non_sequences=None,
mode=None,
name=None):
"""
Similar behaviour as haskell' foldr.
Parameters
----------
fn
The function that ``foldr`` applies at each iteration step
(see ``scan`` for more info).
sequences
List of sequences over which ``foldr`` iterates
(see ``scan`` for more info).
outputs_info
List of dictionaries describing the outputs of reduce
(see ``scan`` for more info).
non_sequences
List of arguments passed to `fn`. ``foldr`` will not iterate over these
arguments (see ``scan`` for more info).
mode
See ``scan``.
name
See ``scan``.
"""
return reduce(fn=fn,
sequences=sequences,
outputs_info=outputs_info,
non_sequences=non_sequences,
go_backwards=True,
mode=mode,
name=name)