We introduce a methodology for obtaining inventories of error results for families of numerical dense linear algebra algorithms. The approach for deriving the analyses is goal-oriented, systematic, and layered. The presentation places the analysis side-by-side with the algorithm so that it is obvious where roundoff error is introduced. The approach supports the analysis of more complex algorith...

Usenet is a widely popular system for organizing and distributing asynchronous discussions, but the newsgroup hierarchies and messages ÒthreadsÓ of Usenet do little to assist users in navigating through the hundreds of thousands of messages that appear on a single day. Messages may be cross-posted to newsgroups in different, even unrelated hierarchies, and threads wander off-topic as people fol...

BACKGROUND Little empirical evidence exists on the effectiveness of using Twitter as a two-way communication tool for public health practice, such as Twitter chats. OBJECTIVE We analyzed whether Twitter chats facilitate engagement in two-way communications between public health entities and their audience. We also describe how to measure two-way communications, incoming and outgoing mentions,...

The composite step biconjugate gradient method (CSBCG) is a simple modification of the standard biconjugate gradient algorithm (BCG) which smooths the sometimes erratic convergence of BCG by computing only a subset of the iterates. We show that 2 × 2 composite steps can cure breakdowns in the biconjugate gradient method caused by (near) singularity of principal submatrices of the tridiagonal ma...

It is of utmost interest to control the divergence of the magnetic flux in simulations of the ideal magnetohydrodynamic equations since, in general, divergence errors tend to accumulate and render the schemes unstable. This paper presents a higher-order extension of the locally divergence-preserving procedure developed in Torrilhon [M. Torrilhon, Locally divergence-preserving upwind finite volu...

Finite precision computations can severely affect the accuracy of computed solutions. We present a complete survey of a static analysis based on abstract interpretation, and a prototype implementing this analysis for C codes, for studying the propagation of rounding errors occurring at every intermediary step in floating-point computations. In the first part of this paper we briefly present all...

Compact models of short channel effect in symmetric and asymmetric double gate MOSFETs are developed by solving two-dimensional (2-D) Poisson’s equation as a boundary value problem in the subthreshold region. The subthreshold current is obtained through the 2-D analytic potential distribution function. Threshold voltage rolloff, drain induced barrier lowering (DIBL) and subthreshold slope degra...

The Lanczos algorithm for matrix tridiagonalisation suffers from strong numerical instability in finite precision arithmetic when applied to evaluate matrix eigenvalues. The mechanism by which this instability arises is well documented in the literature. A recent application of the Lanczos algorithm proposed by Bai, Fahey and Golub allows quadrature evaluation of inner products of the form ψ · ...

In this paper we present a parallel algorithm for the symmetric algebraic eigenvalue problem. The algorithm is based upon a divide and conquer scheme suggested by Cuppen for computing the eigensystem of a symmetric tridiagonal matrix. We extend this idea to obtain a parallel algorithm that retains a number of active parallel processes that is greater than or equal to the initial number througho...

Thare are various systems using Boolean, vector and other models for representation of documents. Each of these models has limitations that do not allow the user to find all relevant documents. This paper describes the approach to retrieving of topic development based on aglomerative clustering. Standard methods of IR does not allow us such kind of queries for appropriate solution of informatio...