## Prop Sum Fast Retract

The prop sum fast retract propagation is activated either by selecting the Prop Sum Fast Retract item of the network menu or by pressing the corresponding button in the run mode tool bar (see figure 1). If you are using auto propagation, you can specify Hugin to use this propagation method.

The prop sum fast retract propagation method can be used in Bbns containing only discrete chance nodes. It is similar to the sum normal method except that it shows the nodes which have recieved evidence differently. Instead of showing the true probability of the states of the node, the probability of the states are shown as if this node had not recieved evidence. That is, the probability of the node being in each of its states given the evidence entered in all other nodes. To indicate that the node has in fact recieved evidence, the belief bars use the color code for evidence (default: Red).

This propagation method can be used to check if the evidence entered in a node meets the probabilities of the evidence or if there are signs of some kind of conflict (the evidence entered is one of the most unlikely states of the node).

Figure 1: The prop sum fast retract button from the run mode tool bar.

Back