5.2. Classification
Classification proceeds as a two-step process. In the first step, a class pruner creates a shortlist of character classes that the unknown might match. Each feature
fetches, from a coarsely quantized 3-dimensional lookup table, a bit-vector of classes that it might match, and
the bit-vectors are summed over all the features. The classes with the highest counts (after correcting for expected number of features) become the short-list for
the next step. Each feature of the unknown looks up a bit vector of prototypes of the given class that it might match, and then the actual similarity between them is computed. Each prototype character class is represented by a logical sum-of-product expression
with each term called a configuration, so the distance calculation process keeps a record of the total similarity evidence of each feature in each configuration, as well as of each prototype. The best combined distance, which is calculated from the summed feature and prototype evidences, is the best over all the stored configurations of the class