A coding view
The sender and receiver use the SBN as a model for
communicating the data.
The sender must stochastically pick a hidden
configuration for each data vector (using random bits
from another message).
The “bits-back” is the entropy of the distribution
across hidden configurations.
Using the chosen configuration, the cost is the energy of
that configuration.
The energy of a complete configuration is just the
cost of sending that configuration
This is the sum over all units of the cost of sending
the state of a unit given the state of its parents (which
has already been sent).