Minoru Asogawa

A connectionist production system which can perform both modus ponens and modus tollens simultaneously

Modus ponens is used in forward inference and backward inference, where the truth of the conclusion is inferred from the truth of the premise. In modus tollens, the falseness of the premise is inferred from the falseness of the conclusion. Although modus ponens is used in general connectionist production systems, modus tollens is rarely used, except in Quinlan’s proposed INFERNO system and in the system proposed by Thornber. A connectionist production system called ConnPS that can perform both modus ponens and modus tollens simultaneously is described. Compared to the INFERNO system, one of the advantages of ConnPS is its supervised learning ability. The rules and examples given as external knowledge are often erroneous and incomplete. In ConnPS, these rules can be refined by using the supervised learning. Both positive and negative examples are presented to ConnPS, onto which the external rules and observations are mapped. Moreover, ConnPS’s implementations of implications, conjunctions, disjunctions and negation are intuitively consistent with Boolean logic.

Parallel tertiary structure search on the Cenju-S parallel machine

The author parallelized a tertiary structure search algorithm on a distributed memory parallel computer, Cenju-S, utilizing a standard message passing interface (MPI) parallel library. For parallelization scheme, a master-workers model is used. The author analyzed the total performance by utilizing a M/M/1 queueing model and Jacksons model, and clearly explained the actual turn around times. Tertiary structure search is a computationally intensive task. When test sequences are distributed to all processors, a single key sequence can be tested independently. Thus high parallelization results are anticipated. Since database is allocated on a master processor, worker processors should acquire test sequences from the master processor. Sometimes a worker should wait until other workers obtain test sequences from the master processor. By this waiting, the total performance will saturate when the number of processors proceeds certain level.