Fast Likelihood Classification

A multistage classification is proposed which reduces the processing time substantially. The proposed classification algorithm consists of several stages, and in each stage likelihood values of classes are calculated and compared. In the proposed multistage classification, if a class has a likelihood value less than a threshold, the class is truncated at that stage as an unlikely class, thus reducing the number of classes for which likelihood values are to be calculated at the next stage. Thus a host of classes can be truncated using a small portion of the total features at early stages, resulting in substantial reduction of computing time. Several truncation criteria are developed and the relationship between thresholds and the error caused by the truncation is investigated. Experiments show that the proposed algorithm reduces the processing time by the factor of 3-7, depending on the number of classes and features, while maintaining essentially the same accuracies.