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Physical Sciences and Mathematics

Selected Works

Hava Siegelmann

Selected Works

1999

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Computational Complexity For Continuous Time Dynamics, Hava Siegelmann, Asa Ben-Hur, Shmuel Fishman Aug 1999

Computational Complexity For Continuous Time Dynamics, Hava Siegelmann, Asa Ben-Hur, Shmuel Fishman

Hava Siegelmann

Dissipative flows model a large variety of physical systems. In this Letter the evolution of such systems is interpreted as a process of computation; the attractor of the dynamics represents the output. A framework for an algorithmic analysis of dissipative flows is presented, enabling the comparison of the performance of discrete and continuous time analog computation models. A simple algorithm for finding the maximum of n numbers is analyzed, and shown to be highly efficient. The notion of tractable (polynomial) computation in the Turing model is conjectured to correspond to computation with tractable (analytically solvable) dynamical systems having polynomial complexity.


Discontinuities In Recurrent Neural Networks, R. Gavaldà, Hava Siegelmann Mar 1999

Discontinuities In Recurrent Neural Networks, R. Gavaldà, Hava Siegelmann

Hava Siegelmann

This article studies the computational power of various discontinuous real computational models that are based on the classical analog recurrent neural network (ARNN). This ARNN consists of finite number of neurons; each neuron computes a polynomial net function and a sigmoid-like continuous activation function. We introduce arithmetic networks as ARNN augmented with a few simple discontinuous (e.g., threshold or zero test) neurons. We argue that even with weights restricted to polynomial time computable reals, arithmetic networks are able to compute arbitrarily complex recursive functions. We identify many types of neural networks that are at least as powerful as arithmetic nets, …