Change the current decay rate for weighted degree to Decay. The decay rate governs how fast the weighted degree decays -- each time a failure occurs during Gecode's constraint propagation, the constraint that failed will have 1 added to its failure count, while all other constraints' failure count is updated by multiplying its old value by the decay rate. The decay rate is a floating point value between 1 (no decay) and 0 (decay to 0 immediately). The weighted degree for a domain variable is the sum of all the failure counts of the constraints that the variable occurs in.