code: protected double getDotProd(int config, FgModel model) {
      	 FeatureVector fv = getFeatures(config);
           return model.dot(fv);
      }
docs: Provide the dot product of the features and model weights for this configuration
  (make sure to exp that value if !logDomain).
  
  Note that this method can be overridden for an efficient product of an ExpFamFactor
  and a hard factor (that rules out some configurations). Just return -infinity
  here before extracting features for configurations that are eliminated by the
  hard factor. If you do this, the corresponding (by config) implementation of
  getFeatures should return an empty vector. This is needed because addExpectedFeatureCounts
  expects to be able to call getFeatures, regardless of whether or not getDotProd has
  ruled it out as having any mass.