copyConnect - connects a group to an IN_, OUT_, or TARGET_COPY group


    copyConnect <source-group> <copy-group> <field>
        [-reset <reset-on-example> | -initOutput <init-output>]


When a group is given the type IN_COPY, OUT_COPY, or TARGET_COPY, it will copy its inputs, outputs, or targets from the units of another, source, group. However, the values needn't be copied from the same field in the units of the source group. For example, inputs to the copy group needn't be copied from the source group's inputs. You could copy the inputs from the outputs or targets or externalInputs of the source group.

Once a group has been given an IN_COPY, OUT_COPY, or TARGET_COPY type, copyConnect must be called to tell it which is its source group and which field of the source group's units the values are to be copied from.

The source and copy groups must have the same number of units.

Valid source group fields are inputs, externalInputs, outputs, targets, inputDerivs, and outputDerivs.

Copying from outputs to outputs is similar to what would happen if you used an ELMAN type rather than OUT_COPY and called elmanConnect, rather than copyConnect. However, these differ in a few important ways. Error is backpropagated across an Elman connection, but not across a copy connection. The Elman connection adds the source values to the outputs, but the copy connection sets the outputs to the source values. Typically, the context group precedes the source group in the group ordering in an Elman connection. But in a copy connection, the copy group will typically follow the source group.

If the copy group has more than one IN_COPY, OUT_COPY, or TARGET_COPY type specified, the copyConnect command applies to the first one that doesn't yet have a source group. Not that you'd ever actually want more than one.


To make group "foo" copy its outputs from the inputs of group "bar" and copy its targets from the outputs of group "baz", do:

    lens> addGroup foo 10 OUT_COPY TARGET_COPY
    lens> copyConnect bar foo inputs
    lens> copyConnect baz foo outputs


addGroup, groupType, elmanConnect

Last modified: Mon Dec 11 12:03:48 EST 2000