Wing Ning Li

On path selection in combinational logic circuits

In order to ascertain correct operation of digital logic circuits it is necessary to verify correct functional operation as well as correct operation at desired clock rates. To ascertain correct operation at desired clock rates signal propagation delays along a set of selected paths are verified to fall within allowed limits by applying appropriate stimuli. Earlier it was suggested that an appropriate set of paths to test would be the one that includes at least one path, with maximum modeled delay, for each circuit lead or gate input. In this paper, algorithms to select such sets of paths with minimum cardinality are given.

Strongly NP-hard discrete gate sizing problems

The discrete gate sizing problem has been studied by several researchers recently. Some complexity results have been obtained, and a number of heuristic algorithms have been proposed. For circuit networks that are restricted to the set of trees, or series-parallel graphs, pseudo-polynomial time algorithms to obtain the exact solution have also been proposed, through none can be extended to arbitrary DAGs (directed acyclic graphs). We prove that the problem is strongly NP-hard. Our results implies that for arbitrary DAGs there is no pseudo-polynomial time algorithm to obtain the exact solution unless P=NP. Our result also provides insight into the difficulties of the problem, and may lead to better heuristics.<<ETX>>

Long and short covering edges in combination logic circuits

The polynomial time algorithm obtained earlier by the authors is extended to find a minimal cardinality path set that long covers each lead or gate input of a digital logic circuit. It is shown how to find, in polynomial time, a minimal cardinality set MinMaxSP for a given combinational logic circuit. Combinational circuit verification is used to verify the sequential circuit delays. >

The complexity of segmented channel routing

The segmented channel routing problem arises in the wiring and the physical design automation for Field Programmable Gate Arrays (FPGAs), a new type of electrically programmable VLSI. It may also be applicable to configurable multiprocessors. This new routing problem poses interesting algorithmic problems. In a previous paper by V. P. Roychowdhury et al. (see ibid., vol.12, no. 1, p. 79-95, 1993), the study of the complexity of segmented channel routing was reported. In this paper, we point out that the strong NP-completeness proof of segmented channel routing in that previous paper is incomplete and incorrect. We provide a correct proof which shows that the problem is indeed NP-complete in the strong sense and, therefore, that an exact polynomial time algorithm for the general case of the problem does not exist unless P=NP. Since our construction also holds for the case where connection lengths are bounded by a constant, we then settle an open question raised by Roychowdhury et al. >

On the circuit implementation problem (combinatorial logic circuits)

The authors consider the problem of selecting an implementation of each circuit module from a cell library to satisfy overall delay and area, or delay and power requirements. Two versions of the circuit implementation problem, the basic circuit implementation problem and the general circuit implementation problem, are shown to be NP-hard. A pseudo-polynomial-time algorithm for the basic circuit implementation problem on series-parallel circuits is developed, and heuristics for the basic circuit implementation problem on general circuits are formulated. The run times for the heuristics are tabulated.<<ETX>>

Identification of Consensus Glycosaminoglycan Binding Strings in Proteins

Heparin is a member of the negatively charged glycosaminoglycan family which is present in the extracellular matrix of all eukaryotic cells. Heparin-binding proteins (HBPs) play an important role in various biological processes like cell signaling, development, and angiogenesis. Interestingly, despite their wide array of functions, very little knowledge exists on the precise structural determinants that govern the specificity of the heparin-protein interaction(s). In this context, a critical survey of the presence of heparin-binding amino acid sequence(s) is a pre-requisite for the development of therapeutic principles against heparin protein-mediated diseases. Many proteins have been shown in vivo to bind to heparin. Based on previous structural studies on heparin-binding proteins (HBPs), nineteen consensus heparin-binding motifs have been identified. The length of these strings varies between five and eight amino acids. These heparin-binding motifs were found to contain a pattern of basic natural amino acids (B= lysine/arginine/histidine) spread between the remaining 17 natural amino acids (X). In the present study, a novel search algorithm has been developed to identify the frequency of occurrence of heparin-binding motifs in 200 proteins which have been experimentally identified to have a strong heparin-binding affinity. The list includes the 23 fibroblast growth factors that bind strongly to heparin, whose sequences were obtained from the UniProt Knowledgebase. Results reveal that the HBPs contain multiple putative heparin-binding motifs. Motifs such as, XBXBX, XBXXBX, and XBXXXBX are most preferred in the heparin-binding proteins. Lysine and arginine are the most preferred basic amino acids (B) in the HBPs. Interestingly, hydrophobic amino acids methionine and isoleucine rarely occur in the heparin-binding motifs. In our opinion, results of our study will enable the design of novel heparin-binding peptides and peptoids which can potentially inhibit heparin mediated pathogenesis. In addition, the algorithm developed in this study can also be of significant use to identify new heparin-binding proteins that have still not been annotated in the human genome databank.

Towards a Domain-Specific Modeling Language for Customer Data Integration Workflow

This paper describes the workflow specification problem, how workflows are specified today, requirements for improved workflow specification, and begins to sketch a new domain-specific modeling language (DSML) approach for specifying intent that can be used to constructively generate a complete workflow meeting a collection of intent requirements. This is an interim report on work in progress.

Data Processing Workflow Automation in Grid Architecture

Because of the poor performance and the expensive license cost, traditional relational database management systems are no longer good choices for processing huge amount of data. Grid computing is replacing the place of RDBMS in data processing. Traditionally a workflow is generated by data experts, which is time consuming, labor intensive and error prone. More over, it becomes the bottleneck of the overall performance of data processing in the grid architecture. This paper proposes a multi-layer workflow automation strategy that can automatically generate a workflow from a business language. A prototype has been implemented and a simulation has been designed

Feedforward backpropagation artificial neural networks on reconfigurable meshes

Abstract The artificial neural networks (ANNs) have been used successfully in applications such as pattern recognition, image processing, automation and control. Majority of todays applications use backpropagate feedforward ANN. In this paper, two methods of P pattern L layer ANN learning on n × n RMESH have been presented. One required memory space of O(nL) but conceptually is simpler to develop and the other uses pipelined approach which reduces the memory requirement to O(L). Both of these algorithms take O(PL) time and are optimal for RMESH architecture.

An efficient algorithm for computing a minimum node cutset from a vertex-disjoint path set for timing optimization

Finding a minimum node cutsef in a delay network is a very itnportanl operarion in Ihe litnitig oplimizarion pime Of (3 number of synfhesis systems. The simplest version of this problem can be described as: Given a network (directed acyclic graph), N = (V, E), with two dislinct vertices s and I (s and L are not connecled by any edge), find a ntinitnwn cardinalily subset of V, V’, such that any path from s lo t uses at 1en~I one member of V’. V’ ti called a tttinimutn node cutset. In this paper, an efficient algorithm for finding a tninitnwn node cutset from a vertex-disjoint path set is proposed. The time complexiry of the algorithm is bounded by 0 (n + e ).