The purpose of this paper is to build the foundation for software architecture. We first develop an intuition for software architecture by appealing to several well-established architectural disciplines. On the basis of this intuition, we present a model of software architec-ture that consists of three components: elements, form, and rationale. Elements are either processing, data, or connecting elements. Form is defined in terms of the properties of, and the relationships among, the elements-- that is, the constraints on the elements. The ratio-nale provides the underlying basis for the architecture in terms of the system constraints, which most often derive from the system:requirements. We discuss the compo-nents of the model in the context of both architectures and architectural styles and present an extended exam-ple to illustrate some important architecture and style considerations. We conclude by presenting some of the benefits of our approach to software architecture, sum-marizing our contributions, and relating our approach to other current work.

Studying the design and implementation of a number of computer has led to some general hints for system design. They are described here and illustrated by many examples, ranging from hardware such as the Alto and the Dorado to application programs such as Bravo and Star. 1.

... quickly across a wide range of hard SAT problems than any other SAT tester in the literature on comparable platforms. On a Sun SPARCStation 10 running SunOS 4.1.3 U1, POSIT can solve hard random 400-variable 3-SAT problems in about 2 hours on the average. In general, it can solve hard n-variable random 3-SAT problems with search trees of size O(2 n=18:7 ). In addition to justifying these claims, this dissertation describes the most significant achievements of other researchers in this area, and discusses all of the widely known general techniques for speeding up SAT search algorithms. It should be useful to anyone interested in NP-complete problems or combinatorial optimization in general, and it should be particularly useful to researchers in either Artificial Intelligence or Operations Research.

Abstract. Dynamic analysis is the analysis of the properties of a run-ning program. In this paper, we explore two new dynamic analyses based on program profiling:- Frequency Spectrum Analysis. We show how analyzing the frequen-cies of program entities in a single execution can help programmers to decompose a program, identify related computations, and find computations related to specific input and output characteristics of a program.- Coverage Concept Analysis. Concept analysis of test coverage data computes dynamic analogs to static control flow relationships such as domination, postdomination, and regions. Comparison of these dynamically computed relationships to their static counterparts can point to areas of code requiring more testing and can aid program-mers in understanding how a program and its test sets relate to one another. 1

This thesis presents "cache-oblivious" algorithms that use asymptotically optimal amounts of work, and move data asymptotically optimally among multiple levels of cache. An algorithm is cache oblivious if no program variables dependent on hardware configuration parameters, such as cache size and cache-line length need to be tuned to minimize the number of cache misses. We show that the ordinary algorithms for matrix transposition, matrix multiplication, sorting, and Jacobi-style multipass filtering are not cache optimal. We present algorithms for rectangular matrix transposition, FFT, sorting, and multipass filters, which are asymptotically optimal on computers with multiple levels of caches. For a cache with size Z and cache-line length L, where Z =# (L 2 ), the number of cache misses for an m × n matrix transpose is #(1 + mn=L). The number of cache misses for either an n-point FFT or the sorting of n numbers is #(1 + (n=L)(1 + log Z n)). The cache complexity of computing n ...

This paper describes FFTW, a portable C package for computing the one- and multidimensional complex discrete Fourier transform (DFT). FFTW is typically faster than all other publicly available DFT software, including the well-known FFTPACK and the code from Numerical Recipes. More interestingly, FFTW is competitive with or better than proprietary, highly-tuned codes such as Sun's Performance Library and IBM's ESSL library. FFTW implements the Cooley-Tukey fast Fourier transform, and is freely available on the Web at http://theory.lcs.mit.edu/fftw. Three main ideas are the keys to FFTW's performance. First, the computation of the transform is performed by an executor consisting of highly-optimized, composable blocks of C code called codelets. Second, at runtime, a planner finds an efficient way (called a `plan') to compose the codelets. Through the planner, FFTW adapts itself to the architecture of the machine it is running on. Third, the codelets are automatically generated by a code...

Abstract—The field of visualization is maturing. Many problems have been solved and new directions are sought. In order to make good choices, an understanding of the purpose and meaning of visualization is needed. In this paper, visualization is considered from multiple points of view. First, a technological viewpoint is adopted, where the value of visualization is measured based on effectiveness and efficiency. An economic model of visualization is presented and benefits and costs are established. Next, consequences and limitations of visualization are discussed (including the use of alternative methods, high initial costs, subjectiveness, and the role of interaction). Example uses of the model for the judgment of existing classes of methods are given to understand why they are or are not used in practice. However, such an economic view is too restrictive. Alternative views on visualization are presented and discussed: visualization as an art, visualization as design and, finally, visualization as a scientific discipline. Index Terms—Visualization, evaluation, validation, methodology, survey, challenges. 1

Basic properties of program predictability -- for both values and control -- are defined and studied. We take the view that program predictability originates at certain points during a program's execution, flows through subsequent instructions, and then ends at other points in the program. These key components of predictability: generation, propagation, and termination; are defined in terms of a model. The model is based on a graph derived from dynamic data dependences and a predictor.

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Ray casting is the bottleneck of many rendering algorithms. Although much work has been done on making ray casting more efficient, most published work is high level. This paper discusses efficiency at a slightly lower level, presenting optimizations for bounding volume hierarchies that many people use but are rarely described in the literature. A set of guidelines for optimization are presented that avoid some of the common pitfalls. Finally, the effects of the optimizations are shown for a set of models. 1