Optimal architectures and algorithms for mesh-connected parallelcomputers with separable row/column buses

A two-dimensional mesh of processing elements (PE's) with separable row and column buses (i.e., broadcast mechanisms for rows and columns that can be logically divided into a number of local buses through the use of PE-controlled switches) has been shown to be quite effective for semigroup computation, prefix computation, and a wide class of other computations that do not require excessive communication or data routing. For meshes with separable row/column buses, the authors show how semigroup and prefix computations can be performed with the same asymptotic time complexity without the provision of buses for every row and every column and discuss the VLSI implications of this new architecture     

An Efficient Universal Addition Scheme for All Hybrid-Redundant Representations with Weighted Bit-Set Encoding

Redundant and hybrid-redundant number representations are used extensively to speed up arithmetic operations within general-purpose and special-purpose digital systems, with the latter (containing both redundant and nonredundant digits) offering cost advantages over fully redundant systems. We use weighted bit-set (WBS) encoding as a paradigm for uniform treatment of five previously studied variants of hybrid-redundant systems. We then extend the class of hybrid-redundant numbers to coincide with the entire set of canonical WBS numbers by allowing an arbitrary nonredundant position, heretofore restricted to ordinary bits (posibits), to hold a negatively weighted bit (negabit). This flexibility leads to interesting and useful symmetric variants of hybrid-redundant representations. We provide a high-level circuit design, based solely on binary full-adders, for a constant-time universal hybrid-redundant adder capable of producing a canonical WBS-encoded sum of two canonical WBS (or extended hybrid) numbers. This is made possible by the use of conventional binary full-adders for reducing any collection of three posibits and negabits, where negabits use an inverted encoding. We compare our adder to previous designs, showing advantages in speed, cost, and regularity. Furthermore we explore representationally closed addition schemes, holding the benefit of greater regularity and reusability, and provide high-level representationally closed designs for all the previously studied variants of hybrid redundancy and for the new symmetric variants introduced here. Finally, we present a new functionality for a conventional (4; 2) compressor in combining any collection of five equally weighted negabits and posibits, and show its utility in the design of multipliers for extended hybrid-redundant numbers. Ghassem Jaberipur received BS in electrical engineering and PhD in computer engineering from Sharif University of Technology in 1974 and 2004, respectively, MS in engineering (majoring in computer hardware) from University of California, Los Angeles, in 1976, and MS in computer science from University of Wisconsin, Madison, in 1979. Since 1979, he has been with the Department of Electrical and Computer Engineering, Shahid Beheshti University, in Tehran, Iran, teaching courses in compiler construction, automata theory, design and implementation of programming languages, and computer arithmetic. Behrooz Parhami (PhD, University of California, Los Angeles, 1973) is Professor of Electrical and Computer Engineering at University of California, Santa Barbara. He has research interests in computer arithmetic, parallel processing, and dependable computing. In his previous position with Sharif University of Technology in Tehran, Iran (1974--88), he was also involved in educational planning, curriculum development, standardization efforts, technology transfer, and various editorial responsibilities, including a five-year term as Editor of Computer Report, a Persian-language computing periodical. His technical publications include over 200 papers in peer-reviewed journals and international conferences, a Persian-language textbook, and an English/Persian glossary of computing terms. Among his publications are three textbooks on parallel processing (Plenum, 1999), computer arithmetic (Oxford, 2000), and computer architecture (Oxford, 2005). Dr. Parhami is a Fellow of both the IEEE and the British Computer Society, a member of the Association for Computing Machinery, and a Distinguished Member of the Informatics Society of Iran for which he served as a founding member and President during 1979-84. He also served as Chairman of IEEE Iran Section (1977-86) and received the IEEE Centennial Medal in 1984. Mohammad Ghodsi Mohammad Ghodsi received BS in electrical engineering from Sharif University of Technology (SUT, Tehran, Iran) in 1975, MS in electrical engineering and computer science from University of California at Berkeley in 1978, and PhD in computer science from the Pennsylvania State University in 1989. He has been affiliated with SUT as a faculty member since 1979. Presently, he is a Professor in SUT's Computer Engineering Department. His research interests include design of efficient algorithms, parallel and systolic algorithms, and computational geometry.     

Data-driven control scheme for linear arrays: application to astable insertion sorter

We present a strategy for designing stable insertion sorters based on linear arrays with data-driven control. The novelty of our approach lies in each data item carrying a control tag to specify how it is to be operated upon by a receiving cell and in performing two parallel comparisons within each cell. To assure first-in/first-out handling of equal key values, some data items must be marked to reflect their past histories. Such marking is conveniently carried out by modifying the data item's control tag. It is the combination of the above features that allows us to derive the first single-cycle priority queue that operates in fully pipelined mode, with no broadcasting of data values or control signals. By performing more than two parallel comparisons in each cell, the VLSI implementation cost of our stable sorter can be reduced. We show that highly cost-effective designs can be obtained by selecting an optimal cell size in terms of the number of comparators it contains     

A taxonomy of voting schemes for data fusion and dependable computation

Voting is an important operation in the fusion of data originating from diverse sources and in the realization of ultrareliable systems based on multiple computation channels. Voting involves the derivation of an output data object from a collection of n input data objects, as prescribed by the requirements and constraints of a voting algorithm. The objects voted on can be quite complex in terms of content and, explicitly specified or implicit, structure. Regardless of implementation details (e.g., whether realized in hardware, software, or hybrid schemes) and object space properties, voting algorithms can be classified according to how they view the input and output data objects and how they handle the votes (weights) at input and output. A 16-class (binary 4-cube) categorization results from dichotomizing each of the above voter features. This categorization leads to an abstraction that helps in the study of voting algorithms with regard to the dependability level for the outputs and the speed at which they are obtained; viz, the quality and efficiency of the algorithms. The taxonomy is broad enough to cover, and detailed enough to distinguish among, a wide variety of commonly used voting algorithms in data fusion and dependable computation. It also provides insight into the relationships of various voting schemes and facilitates comparison and fine-tuning of such algorithms.     

Identification of Anti-Severe Acute Respiratory Syndrome-Related Coronavirus 2 (SARS-CoV-2) Oxysterol Derivatives In Vitro

The development of effective antiviral drugs targeting the severe acute respiratory syndrome-related coronavirus 2 (SARS-CoV-2) is urgently needed to combat the coronavirus disease 2019 (COVID-19). We have previously studied the use of semi-synthetic derivatives of oxysterols, oxidized derivatives of cholesterol as drug candidates for the inhibition of cancer, fibrosis, and bone regeneration. In this study, we screened a panel of naturally occurring and semi-synthetic oxysterols for anti-SARS-CoV-2 activity using a cell culture infection assay. We show that the natural oxysterols, 7-ketocholesterol, 22(R)-hydroxycholesterol, 24(S)-hydroxycholesterol, and 27-hydroxycholesterol, substantially inhibited SARS-CoV-2 propagation in cultured cells. Among semi-synthetic oxysterols, Oxy210 and Oxy232 displayed more robust anti-SARS-CoV-2 activities, reducing viral replication more than 90% at 10 μM and 99% at 15 μM, respectively. When orally administered in mice, peak plasma concentrations of Oxy210 fell into a therapeutically relevant range (19 μM), based on the dose-dependent curve for antiviral activity in our cell-based assay. Mechanistic studies suggest that Oxy210 reduced replication of SARS-CoV-2 by disrupting the formation of double-membrane vesicles (DMVs); intracellular membrane compartments associated with viral replication. Our study warrants further evaluation of Oxy210 and Oxy232 as a safe and reliable oral medication, which could help protect vulnerable populations with increased risk of developing COVID-19.     

Effects of high-dose fish oil on rheumatoid arthritis after stopping nonsteroidal antiinflammatory drugs. Clinical and immune correlates

OBJECTIVE: To determine the following: 1) whether dietary supplementation with fish oil will allow the discontinuation of nonsteroidal antiinflammatory drugs (NSAIDs) in patients with rheumatoid arthritis (RA); 2) the clinical efficacy of high-dose dietary omega 3 fatty acid fish oil supplementation in RA patients; and 3) the effect of fish oil supplements on the production of multiple cytokines in this population. METHODS: Sixty-six RA patients entered a double-blind, placebo-controlled, prospective study of fish oil supplementation while taking diclofenac (75 mg twice a day). Patients took either 130 mg/kg/day of omega 3 fatty acids or 9 capsules/day of corn oil. Placebo diclofenac was substituted at week 18 or 22, and fish oil supplements were continued for 8 weeks (to week 26 or 30). Serum levels of interleukin-1 beta (IL-1 beta), IL-2, IL-6, and IL-8 and tumor necrosis factor alpha were measured by enzyme-linked immunosorbent assay at baseline and during the study. RESULTS: In the group taking fish oil, there were significant decreases from baseline in the mean (+/- SEM) number of tender joints (5.3 +/- 0.835; P < 0.0001), duration of morning stiffness (-67.7 +/- 23.3 minutes; P = 0.008), physician's and patient's evaluation of global arthritis activity (-0.33 +/- 0.13; P = 0.017 and -0.38 +/- 0.17; P = 0.036, respectively), and physician's evaluation of pain (-0.38 +/- 0.12; P = 0.004). In patients taking corn oil, no clinical parameters improved from baseline. The decrease in the number of tender joints remained significant 8 weeks after discontinuing diclofenac in patients taking fish oil (-7.8 +/- 2.6; P = 0.011) and the decrease in the number of tender joints at this time was significant compared with that in patients receiving corn oil (P = 0.043). IL-1 beta decreased significantly from baseline through weeks 18 and 22 in patients consuming fish oil (-7.7 +/- 3.1; P = 0.026). CONCLUSION: Patients taking dietary supplements of fish oil exhibit improvements in clinical parameters of disease activity from baseline, including the number of tender joints, and these improvements are associated with significant decreases in levels of IL-1 beta from baseline. Some patients who take fish oil are able to discontinue NSAIDs without experiencing a disease flare.     

Comparison of sulfasalazine and placebo in the treatment of reactive arthritis (Reiter's syndrome). A Department of Veterans Affairs Cooperative Study

OBJECTIVE: To determine whether sulfasalazine (SSZ) at a dosage of 2,000 mg/day is effective in the treatment of reactive arthritis (ReA) that has been unresponsive to nonsteroidal antiinflammatory drug (NSAID) therapy. METHODS: One hundred thirty-four patients with ReA who had failed to respond to NSAIDs were recruited from 19 clinics, randomized (double-blind) to receive either SSZ or placebo, and followed up for 36 weeks. The definition of treatment response was based on joint pain/tenderness and swelling scores and physician and patient global assessments. RESULTS: Longitudinal analysis revealed improvement in the patients taking SSZ compared with those taking placebo, which appeared at 4 weeks and continued through the trial (P = 0.02). At the end of treatment, response rates were 62.3% for SSZ treatment compared with 47.7% for placebo treatment. The Westergren erythrocyte sedimentation rate declined more with SSZ treatment than with placebo (P < 0.0001). Adverse reactions were fewer than expected and were mainly due to nonspecific gastrointestinal complaints. CONCLUSION: SSZ at a dosage of 2,000 mg/day is well tolerated and effective in patients with chronically active ReA.     

An efficient approach for evaluating Sommerfeld integrals encountered in the problem of a current element radiating over lossy ground

Efficient numerical evaluation of the Sommerfeld integrals, arising from the problem of a current element radiating over a lossy half-space, is considered. An integration technique based on the method of steepest descent is investigated. The details for computing possible pole and branch cut contributions resulting from the deformation of the path of integration are presented. A computer program for evaluating Sommerfeld integrals is developed on the analysis presented. Numerical results and estimates of computational efficiency of the method are given and a comparison with other available works in the literature is included.     

Perfect difference networks and related interconnection structures for parallel and distributed systems

In view of their applicability to parallel and distributed computer systems, interconnection networks have been studied intensively by mathematicians, computer scientists, and computer designers. In this paper, we propose an asymptotically optimal method for connecting a set of nodes into a perfect difference network (PDN) with diameter 2, so that any node is reachable from any other node in one or two hops. The PDN interconnection scheme, which is based on the mathematical notion of perfect difference sets, is optimal in the sense that it can accommodate an asymptotically maximal number of nodes with smallest possible node degree under the constraint of the network diameter being 2. We present the network architecture in its basic and bipartite forms and show how the related multidimensional PDNs can be derived. We derive the exact average internode distance and tight upper and lower bounds for the bisection width of a PDN. We conclude that PDNs and their derivatives constitute worthy additions to the repertoire of network designers and may offer additional design points that can be exploited by current and emerging technologies, including wireless and optical interconnects. Performance, algorithmic, and robustness attributes of PDNs are analyzed in a companion paper.