Package topo :: Package base :: Module projection :: Class ProjectionSheet

Class ProjectionSheet

                       object --+            
                                |            
param.parameterized.Parameterized --+        
                                    |        
            simulation.EventProcessor --+    
                                        |    
                           object --+   |    
                                    |   |    
    sheetcoords.SheetCoordinateSystem --+    
                                        |    
                              sheet.Sheet --+
                                            |
                                           ProjectionSheet

Known Subclasses:

cf.CFSheet

A Sheet whose activity is computed using Projections from other sheets.

A standard ProjectionSheet expects its input to be generated from other Sheets. Upon receiving an input event, the ProjectionSheet interprets the event data to be (a copy of) an activity matrix from another sheet. The ProjectionSheet provides a copy of this matrix to each Projection from that input Sheet, asking each one to compute their own activity in response. The same occurs for any other pending input events.

After all events have been processed for a given time, the ProjectionSheet computes its own activity matrix using its activate() method, which by default sums all its Projections' activity matrices and passes the result through a user-specified output_fn() before sending it out on the default output port. The activate() method can be overridden to sum some of the projections, multiply that by the sum of other projections, etc., to model modulatory or other more complicated types of connections.

The output_fn is a function s(A) that takes an activity matrix A and produces an identically shaped output matrix. The default is the identity function.

Nested Classes

[hide private]

Inherited from param.parameterized.Parameterized: __metaclass__

Instance Methods

[hide private]

__init__(self, **params)
x.__init__(...) initializes x; see x.__class__.__doc__ for signature

source code

_dest_connect(self, conn)
See EventProcessor's _dest_connect(); raises an error if conn is not a Projection.

source code

_grouped_in_projections(self, ptype)
Return a dictionary of lists of incoming Projections, grouped by type.

source code

_port_match(self, key, portlist)
Returns True if the given key matches any port on the given list.

source code

activate(self)
Collect activity from each projection, combine it to calculate the activity for this sheet, and send the result out.

source code

input_event(self, conn, data)
Accept input from some sheet.

source code

learn(self)
By default, call the learn() and apply_learn_output_fn() methods on every Projection to this Sheet.

source code

override_plasticity_state(self, new_plasticity_state)
Temporarily override plasticity state of medium and long term internal state.

source code

present_input(self, input_activity, conn)
Provide the given input_activity to each in_projection that has a dest_port equal to the specified port, asking each one to compute its activity.

source code

process_current_time(self)
Called by the simulation after all the events are processed for the current time but before time advances.

source code

projections(self, name=None)
Return either a named input p, or a dictionary {projection_name, projection} of all the in_connections for this ProjectionSheet.

source code

restore_plasticity_state(self)
Restores plasticity of medium and long term internal state after a override_plasticity_state call.

source code

Inherited from sheet.Sheet: activity_len, release_sheet_view, row_col_sheetcoords, sheet_cols, sheet_offset, sheet_rows, state_pop, state_push

Inherited from sheet.Sheet (private): _get_density

Inherited from simulation.EventProcessor: script_repr, send_output, start

Inherited from simulation.EventProcessor (private): _src_connect

Inherited from param.parameterized.Parameterized: __getstate__, __repr__, __setstate__, __str__, debug, defaults, force_new_dynamic_value, get_param_values, get_value_generator, inspect_value, message, print_param_values, set_dynamic_time_fn, verbose, warning

Inherited from param.parameterized.Parameterized (private): _check_params, _instantiate_param, _set_name, _setup_params

Inherited from sheetcoords.SheetCoordinateSystem: closest_cell_center, matrix2sheet, matrixidx2sheet, sheet2matrix, sheet2matrixidx, sheetcoordinates_of_matrixidx

Inherited from object: __delattr__, __getattribute__, __hash__, __new__, __reduce__, __reduce_ex__, __setattr__

Class Methods

[hide private]

Inherited from param.parameterized.Parameterized: params, print_param_defaults

Class Variables

[hide private]

apply_output_fn = param.Boolean(default= True, doc= "Whether t...
Whether to apply the output_fn after computing an Activity matrix.

dest_ports = ['Activity']
list() -> new list list(sequence) -> new list initialized from sequence's items

divisive_constant = param.Number(default= 1.0, doc= ...
Constant value added to projection activity before combining divisively.

mask = param.Parameter(default= SheetMask(), instantiate= True...
SheetMask object for computing which units need to be computed further.

multiplicative_constant = param.Number(default= 0.0, doc= ...
Constant value added to projection activity before combining multiplicatively.

output_fn = param.ClassSelector(OutputFn, default= IdentityOF(...
Output function to apply (if apply_output_fn is true) to this Sheet's activity.

src_ports = ['Activity']
list() -> new list list(sequence) -> new list initialized from sequence's items

Inherited from sheet.Sheet: layout_location, nominal_bounds, nominal_density, plastic, precedence

Inherited from param.parameterized.Parameterized: name, print_level

Properties

[hide private]

Inherited from sheet.Sheet: density

Inherited from sheetcoords.SheetCoordinateSystem: shape, xdensity, ydensity

Inherited from object: __class__

Method Details

[hide private]

init(self, **params)
(Constructor)

source code

x.__init__(...) initializes x; see x.__class__.__doc__ for signature

Overrides: object.__init__: (inherited documentation)

_dest_connect(self, conn)

source code

See EventProcessor's _dest_connect(); raises an error if conn is not a Projection. Subclasses of ProjectionSheet that know how to handle other types of Connections should override this method.

Overrides: simulation.EventProcessor._dest_connect

_grouped_in_projections(self, ptype)

source code

Return a dictionary of lists of incoming Projections, grouped by type.

Each projection of type <ptype> is grouped according to the name of the port, into a single list within the dictionary.

The entry None will contain those that are not of type <ptype>, while the other entries will contain a list of Projections, each of which has type ptype.

Example: to obtain the lists of projections that should be jointly normalised together, call __grouped_in_projection('JointNormalize').

_port_match(self, key, portlist)

source code

Returns True if the given key matches any port on the given list.

A port is considered a match if the port is == to the key, or if the port is a tuple whose first element is == to the key, or if both the key and the port are tuples whose first elements are ==.

This approach allows connections to be grouped using tuples.

Overrides: simulation.EventProcessor._port_match

activate(self)

source code

Collect activity from each projection, combine it to calculate the activity for this sheet, and send the result out.

Subclasses may override this method to whatever it means to calculate activity in that subclass.

input_event(self, conn, data)

source code

Accept input from some sheet. Call .present_input() to compute the stimulation from that sheet.

Overrides: simulation.EventProcessor.input_event

learn(self)

source code

By default, call the learn() and apply_learn_output_fn() methods on every Projection to this Sheet.

Any other type of learning can be implemented by overriding this method. Called from self.process_current_time() _after_ activity has been propagated.

override_plasticity_state(self, new_plasticity_state)

source code

Temporarily override plasticity state of medium and long term internal state.

This function should be implemented by all subclasses so that when new_plasticity_state=False, it preserves the ability of the ProjectionSheet to compute activity, i.e. to operate over a short time scale, while preventing any lasting changes to the state.

Any process that does not have any lasting state, such as those affecting only the current activity level, should not be affected by this call.

By default, calls override_plasticity_state() on the ProjectionSheet's output_fn and all of its incoming Projections, and also enables the 'plastic' parameter for this ProjectionSheet. The old value of the plastic parameter is saved to an internal stack to be restored by restore_plasticity_state().

Overrides: sheet.Sheet.override_plasticity_state

present_input(self, input_activity, conn)

source code

Provide the given input_activity to each in_projection that has a dest_port equal to the specified port, asking each one to compute its activity.

The sheet's own activity is not calculated until activate() is called.

process_current_time(self)

source code

Called by the simulation after all the events are processed for the current time but before time advances. Allows the event processor to send any events that must be sent before time advances to drive the simulation.

Overrides: simulation.EventProcessor.process_current_time

projections(self, name=None)

source code

Return either a named input p, or a dictionary {projection_name, projection} of all the in_connections for this ProjectionSheet.

A minor convenience function for finding projections by name; the sheet's list of in_connections usually provides simpler access to the Projections.

restore_plasticity_state(self)

source code

Restores plasticity of medium and long term internal state after a override_plasticity_state call.

This function should be implemented by all subclasses to remove the effect of the most recent override_plasticity_state call, i.e. to restore plasticity of any type that was overridden.

Overrides: sheet.Sheet.restore_plasticity_state: (inherited documentation)

Class Variable Details

[hide private]

apply_output_fn

Whether to apply the output_fn after computing an Activity matrix.

Value:

param.Boolean(default= True, doc= "Whether to apply the output_fn after computing 
an Activity matrix.")

divisive_constant

Constant value added to projection activity before combining divisively.

Value:

param.Number(default= 1.0, doc= """
        Constant value added to projection activity before combining divisively.""
")

mask

SheetMask object for computing which units need to be computed further. The object should be an instance of SheetMask, and will compute which neurons will be considered active for the purposes of further processing. The default mask effectively disables all masking, but subclasses can use this mask to implement optimizations, non-rectangular Sheet shapes, lesions, etc.

Value:

param.Parameter(default= SheetMask(), instantiate= True, doc= """
        SheetMask object for computing which units need to be computed further.
        The object should be an instance of SheetMask, and will
        compute which neurons will be considered active for the
        purposes of further processing.  The default mask effectively
        disables all masking, but subclasses can use this mask to
        implement optimizations, non-rectangular Sheet shapes,
        lesions, etc.""")

multiplicative_constant

Constant value added to projection activity before combining multiplicatively.

Value:

param.Number(default= 0.0, doc= """
        Constant value added to projection activity before combining multiplicativ
ely.""")

output_fn

Output function to apply (if apply_output_fn is true) to this Sheet's activity.

Value:

param.ClassSelector(OutputFn, default= IdentityOF(), doc= "Output function to appl
y (if apply_output_fn is true) to this Sheet's activity.")

Class ProjectionSheet

__init__(self, **params) (Constructor)

_dest_connect(self, conn)

_grouped_in_projections(self, ptype)

_port_match(self, key, portlist)

activate(self)

input_event(self, conn, data)

learn(self)

override_plasticity_state(self, new_plasticity_state)

present_input(self, input_activity, conn)

process_current_time(self)

projections(self, name=None)

restore_plasticity_state(self)

apply_output_fn

divisive_constant

mask

multiplicative_constant

output_fn

init(self, **params)
(Constructor)