Showing papers by "AT&T Labs published in 1989"

Efficient distributed event-driven simulations of multiple-loop networks

Abstract: Simulating asynchronous multiple-loop networks is commonly considered a difficult task for parallel programming. Two examples of asynchronous multiple-loop networks are presented in this article: a stylized queuing system and an Ising model. In both cases, the network is an n × n grid on a torus and includes at least an order of n2 feedback loops. A new distributed simulation algorithm is demonstrated on these two examples. The algorithm combines three elements: (1) the bounded lag restriction; (2) minimum propagation delays; and (3) the so-called opaque periods. We prove that if N processing elements (PEs) execute the algorithm in parallel and the simulated system exhibits sufficient density of events, then, on average, processing one event would require O(log N) instructions of one PE. Experiments on a shared memory MIMD bus computer (Sequent's Balance) and on a SIMD computer (Connection Machine) show speed-ups greater than 16 on 25 PEs of a Balance and greater than1900 on 214 PEs of a Connection Machine.

The new KornShell command and programming language

Abstract: From the Publisher: This is a Second Edition of the bestselling guide to the KornShell command and programming language by the original inventors of the language. It provides a specification for the KornShell language, tutorial material for those new to ksh (the program that implements the KornShell language), and a comprehensive reference for all ksh users. Covers major new additions to the KornShell language ksh93 (including command completion and a key binding mechanism); provides tutorials for both of the functions of ksh (as an interactive command language, and as a programming language); contains numerous examples illustrating the features of ksh; and features a Quick Reference summary of the KornShell language with page references to the book. For both new users with little shell experience, and for experienced computer users who are familiar with ksh and/or other shells. ISBN of 1st Edition: 01351697202.

Incorporating syntax into the level-building algorithm on a tree-structured parallel computer

Abstract: The authors investigate the parallel computation of large-vocabulary speech recognition on a tree-structured parallel processor. Having seriously established results on parallel level-building with continuously variable hidden Markov models they extend this work to the case in which the spoken sentences are constrained by a finite state grammar. The two key ideas are: (1) a pipelined sorting function on the processor array that efficiently transmits a sorted list of the best scores from all processors to the host; and (2) a level-based pruning technique in which paths through the dynamic programming network are pruned only at the ends of words. These ideas are evaluated on the BT-100 processor, a binary-tree parallel processor. A performance model is presented that estimates execution time as a function of algorithm parameters. Real-time speech recognition has been achieved for a data-entry task with a 70-word vocabulary and average branching factor of 23, and for an airline reservation task with a vocabulary of 132 words. The performance model predicts real-time execution of the 991-word DARPA Resource Management Task on a 127-processor machine. >

Radiation-enhanced diffusion of implanted impurities in amorphous Si

Abstract: We have investigated radiation-enhanced diffusion of impurities implanted in amorphous Si. Results will be reported for Cu, Ag, Au, As, In, Sb, Fe and Pt bombarded with 2.5 MeV Ar in the temperature range 77–770 K. At low temperatures an athermal diffusive process, probably due to ballistic mixing, is observed. At intermediate temperatures, for Cu, Ag and Au, the diffusion is noticeably enhanced over the usual thermal values and the process is thermally activated with activation energies in the range 0.25–0.4 eV. At higher temperatures pure thermal diffusion dominates. For the other impurities no radiation enhancement of the diffusion has been observed.