Fig 1. An example of a compressed trellis for a three-state model with states labeled +, − and =.

Within each block, only self-transitions are allowed. Relevant variables such as the forward or backward variables are computed for each block instead of for each individual observation. Our evaluation demonstrates that for compressible input, i.e., input with large average block sizes, the compressed computation has a neglible impact on accuracy while accelerating computations greatly, in particular for models with many states.