Publications (12)4.98 Total impact

Conference Paper: Minimization of the Number of Edges in an EVMDD by Variable Grouping for Fast Analysis of MultiState Systems
[Show abstract] [Hide abstract]
ABSTRACT: This paper proposes an algorithm to minimize the number of edges in an edgevalued multivalued decision diagram (EVMDD) for fast analysis of multistate systems. We minimize the number of edges by grouping multivalued variables into largervalued variables. By grouping multivalued variables, we can also reduce the number of nodes. However, minimization of the number of nodes by grouping variables is not always effective for fast analysis of multistate systems. On the other hand, minimization of the number of edges is effective. Experimental results show that the proposed algorithm for minimizing the number of edges reduces the number of edges by up to 15% and the number of nodes by up to 47%. This results in a speedup of the analysis of multistate systems by about three times.MultipleValued Logic (ISMVL), 2013 IEEE 43rd International Symposium on; 05/2013 
Conference Paper: Hardware Index to Permutation Converter
[Show abstract] [Hide abstract]
ABSTRACT: We demonstrate a circuit that generates a permutation in response to an index. Since there are n! nelement permutations, the index ranges from 0 to n!  1. Such a circuit is needed in the hardware implementation of uniquepermutation hash functions to specify how parallel machines interact through a shared memory. Such a circuit is also needed in cryptographic applications. The circuit is based on the factorial number system. Here, each nonnegative integer is uniquely represented as sn1(n  1)! + sn2(n  2)! +. . . + s11!, where 1 ≤ si ≤ i. That is, the permutation is produced by generating the digits si in the factorial number system representation of the index. The circuit is combinational and is easily pipelined to produce one permutation per clock period. We give experimental results that show the efficiency of our designs. For example. we show that the rate of production of permutations on the SRC6 reconfigurable computer is 1,820 times faster than a program on a conventional microprocessor in the case of 10element permutations. We also show an efficient reconfigurable computer implementation that produces random permutations using the Knuth shuffle algorithm. This is useful in Monte Carlo simulations. For both circuits, the complexity is O(n2), and the delay is O(n).Parallel and Distributed Processing Symposium Workshops & PhD Forum (IPDPSW), 2012 IEEE 26th International; 01/2012 
Conference Paper: Numeric Function Generators Using Piecewise Arithmetic Expressions
[Show abstract] [Hide abstract]
ABSTRACT: This paper proposes new architectures for numeric function generators (NFGs) using piecewise arithmetic expressions. The proposed architectures are programmable, and they realize a wide range of numeric functions. To design an NFG for a given function, we partition the domain of the function into uniform segments, and transform a subfunction in each segment into an arithmetic spectrum. From this arithmetic spectrum, we derive an arithmetic expression, and realize the arithmetic expression with hardware. Since the arithmetic spectrum has many zero coefficients and repeated coefficients, by storing only distinct nonzero coefficients in a table, we can significantly reduce the table size needed to store arithmetic coefficients. Experimental results show that the table size can be reduced to only a small percent of the table size needed to store all the arithmetic coefficients. We also propose techniques to reduce table size further and to improve performance.MultipleValued Logic (ISMVL), 2011 41st IEEE International Symposium on; 06/2011 
Article: Numeric Function Generators
[Show abstract] [Hide abstract]
ABSTRACT: We show the architecture and design of a numeric function generator that realizes, at high speed, arithmetic functions, like log x, sin x, 1 x , etc.. This approach is general; different circuits are not needed for different functions. Further, composite functions, like log (sin ( 1 x )) can be realized as easily as individual functions. A tutorial description of the method is presented, followed by descriptions of the design considerations that must be made. For example, we discuss how circuit complexity increases as the desired approximation error decreases. Also, we discuss enhancements of the basic numeric function generator approach, including higher order polynomial approximations, floating point, and multivariable implementations.  [Show abstract] [Hide abstract]
ABSTRACT: The traditional problem in binary decision diagrams (BDDs) has been to minimize the number of nodes since this reduces the memory needed to store the BDD. Recently, a new problem has emerged: minimizing the average path length (APL). APL is a measure of the time needed to evaluate the function by applying a sequence of variable values. It is of special significance when BDDs are used in simulation and design verification. A main result of this paper is that the APL for benchmark functions is typically much smaller than for random functions. That is, for the set of all functions, we show that the average APL is close to the maximum path length, whereas benchmark functions show a remarkably small APL. Surprisingly, however, typical functions do not achieve the absolute maximum APL. We show that the parity functions are unique in having that distinction. We show that the APL of a BDD can vary considerably with variable ordering. We derive the APL for various functions, including the AND, OR, threshold, Achilles' heel, and certain arithmetic functions. We show that the unate cascade functions uniquely achieve the absolute minimum APL.IEEE Transactions on Computers 10/2005; 54(9):1041 1053. DOI:10.1109/TC.2005.137 · 1.66 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: The availability of large, inexpensive memory has made it possible to realize numerical functions, such as the reciprocal, square root, and trigonometric functions, using a lookup table. This is much faster than by software. However, a naive lookup method requires unreasonably large memory. In this paper, we show the use of a lookup table (LUT) cascade to realize a piecewise linear approximation to the given function. Our approach yields memory of reasonable size and significant accuracy.  [Show abstract] [Hide abstract]
ABSTRACT: This paper focuses on the average path length (APL) of BDD's for switching functions. APL is a metric for the time it takes to evaluate the function by a computer program. We derive the APL for the AND, OR, parity, carryout, comparison, threshold symmetric, and majority functions. We also consider the average of the APL for various classes of functions, including symmetric, threshold symmetric, and unate cascade. For symmetric functions, we show the average APL is close to the maximum path length, n, the number of variables. We show there are exactly two functions, the parity functions, that achieve the upper bound, n, on the APL for BDD's over all functions dependent on n variables. All other functions have an APL strictly less than n. We show that the APL of BDD's over all functions dependent on n variables is bounded below by 2 − 1 2 n−1 . The set of functions that achieves this small value is uniquely the set of unate cascade realizable functions. We also show that the APL for benchmark functions is typically much less than for random functions.  [Show abstract] [Hide abstract]
ABSTRACT: In an irredundant sumofproducts expression (ISOP), each product is a prime implicant (Pl) and no product can be deleted without changing the function. Among the ISOPs for some function f, a worst ISOP (WSOP) is an ISOP with the largest number of Pls and a minimum ISOP (MSOP) is one with the smallest number. We show a class of functions for which the MinatoMorreale ISOP algorithm produces WSOPs. Since the ratio of the size of the WSOP to the size of the MSOP is arbitrarily large when it, the number of variables, is unbounded, the MinatoMorreale algorithm can produce results that are very far from minimum. We present a class of multipleoutput functions whose WSOP size is also much larger than its MSOP size. For a set of benchmark functions, we show the distribution of ISOPs to the number of Pls. Among this set are functions where the MSOPs have almost as many Pls as do the WSOPs. These functions are known to be easy to minimize. Also, there are benchmark functions where the fraction of ISOPs that are MSOPs is small and MSOPs have many fewer Pls than the WSOPs. Such functions are known to be hard to minimize. For one class of functions, we show that the fraction of ISOPs that are MSOPs approaches 0 as n approaches infinity, suggesting that such functions are hard to minimizeIEEE Transactions on Computers 09/2001; 50(9):935948. DOI:10.1109/12.954508 · 1.66 Impact Factor 
Conference Paper: On the minimization of SOPs for bidecomposable functions
[Show abstract] [Hide abstract]
ABSTRACT: A function f is AND bidecomposable if it can be written as f(X <sub>1</sub>,X<sub>2</sub>)=h<sub>1</sub>(X<sub>1</sub>)h<sub>2</sub>(X <sub>2</sub>). In this case, a sumofproducts expression (SOP) for f is obtained from minimum SOPs (MSOP) for h<sub>1</sub> and h<sub>2</sub> by applying the law of distributivity. If the result is an MSOP, then the complexity of minimization is reduced. However, the application of the law of distributivity to MSOPs for h<sub>1</sub> and h<sub>2</sub> does not always produce an MSOP for f. We show an incompletely specified function of n(n1) variables that requires at most n products in an MSOP, while 2<sup>n1</sup> products are required by minimizing the component functions separately. We introduce a new class of logic functions, called orthodox functions, where the application of the law of distributivity to MSOPs for component functions of f always produces an MSOP for f. We show that orthodox functions include all functions with three of fewer variables, all symmetric functions, all unate functions, many benchmark functions, and few random functions with many variablesDesign Automation Conference, 2001. Proceedings of the ASPDAC 2001. Asia and South Pacific; 02/2001 
Article: Average and worst case number of nodes in decision diagrams of symmetric multiplevalued functions
[Show abstract] [Hide abstract]
ABSTRACT: We derive the average and worst case number of nodes in decision diagrams of rvalued symmetric functions of n variables. We show that, for large n, both numbers approach nr/rl. For binary decision diagrams (r=2), we compute the distribution of the number of functions on n variables with a specified number of nodes. Subclasses of symmetric functions appear as features in this distribution. For example, voting functions are noted as having an average of n2/6 nodes, for large n, compared to n2/2, for general binary symmetric functionsIEEE Transactions on Computers 04/1997; 46(4):491494. DOI:10.1109/12.588065 · 1.66 Impact Factor 
Conference Paper: A method to represent multipleoutput switching functions by using multivalued decision diagrams
[Show abstract] [Hide abstract]
ABSTRACT: Multipleoutput switching functions can be simulated by multiplevalued decision diagrams (MDDs) at a significant reduction in computation time. analyze the following approaches to the representation problem: shared multiplevalued decision diagrams (SMDDs), multiterminal multiplevalued decision diagrams (MTMDDs), and shared multiterminal multiplevalued decision diagrams(SMTMDDs). For example, we show that SMDDs fend to be compact, while SMTMDDs tend to be fast. We present an algorithm for grouping input variables and output functions in the MDDsMultipleValued Logic, 1996. Proceedings., 26th International Symposium on; 06/1996  [Show abstract] [Hide abstract]
ABSTRACT: We introduce eigenfunctions of the ReedMuller transform. Eigenfunctions are functions whose canonical sumofproducts expression and PPRM (positive polarity ReedMuller expression) are isomorphic. In the case of symmetric functions, the eigenfunction can be viewed as a function whose reduced truth vector is identical to the reduced ReedMuller spectrum. We show that the number of symmetric (ordinary) eigenfunctions on Òvariables is ¾ Ò·½ ¾ (¾ ¾ Ò½).
Publication Stats
131  Citations  
4.98  Total Impact Points  
Top Journals
Institutions

19972012

Naval Postgraduate School
 Department of Electrical and Computer Engineering
Monterey, California, United States


2001

Kyushu Institute of Technology
 Department of Computer Science
Hukuoka, Fukuoka, Japan
