Model¶
A model in Blocks is simply an annotated computation graph. The class
Model
extends blocks.graph.ComputationGraph
:class:,
which is able to handle annotations and roles in general, but is
deliberately made unaware of specific annotations that a Theano graph
created by Blocks typically has, such as bricks and application calls. The
Model
adds this functionality. Using Model
you can do
things like query all the bricks used to build the computation graph,
request “hierarchical names” of the parameters (a hierarchical name is a
pathlike string which in addition to the parameter’s name contains names
of the bricks on the path from a root brick to the brick that owns the
parameters, e.g. /mlp/linear/W
).
For more information, see Model
docstring.

class
blocks.model.
Model
(*args, **kwargs)[source]¶ Bases:
blocks.graph.ComputationGraph
Handles annotations in Blocksbuilt computation graphs.
Use this class to handle your Blockscreated computation graph.
Examples
>>> from theano import tensor >>> from blocks.bricks import MLP, Tanh >>> x = tensor.matrix('x') >>> mlp = MLP([Tanh(), Tanh()], [10, 10, 10]) >>> y = mlp.apply(x) >>> model = Model(y)
With
Model
you can get access to the brick hierarchy. The brick hierarchy is defined bychildren
attributes that every brick has. The bricks that are not children of other bricks are called top bricks. It is often useful to have access to top bricks of a brick hierarchy used to build a computation graph, and here is how you can do it:>>> model.get_top_bricks() [<blocks.bricks.sequences.MLP object at ...]
You can also get “hierarchical” names for the parameters, which encode the position of the owning brick in the brick hierarchy.
>>> model.get_parameter_dict() OrderedDict([('/mlp/linear_1.b', b), ('/mlp/linear_0.b', b), ('/mlp/linear_0.W', W), ('/mlp/linear_1.W', W)])

get_parameter_dict
()[source]¶ Returns parameters with their hierarchical names.
The parameter names are formed from positions of their owner bricks in the bricks hierarchy. The variable names are used for the parameters that do not belong to any brick.
Returns: parameter_dict – A dictionary of (hierarchical name, shared variable) pairs. Return type: dict

get_parameter_values
()[source]¶ Return the values of model parameters.
The same hierarhical names as in
get_parameter_dict()
are used to uniquely identify parameters.Returns: parameter_values – Dictionary of (hierarchical name, ndarray
) pairs.Return type: OrderedDict

get_top_bricks
()[source]¶ Get the bricks that do not have parents.
Returns: bricks Return type: list of Brick

set_parameter_values
(parameter_values)[source]¶ Set the values of model parameters.
The same hierarhical names as in
get_parameter_dict()
are used to uniquely identify parameters.Parameters: parameter_values (OrderedDict) – Dictionary of (hierarchical name, ndarray
) pairs.
