Control Flow Model Research Articles

A new implementation of the Icon language

Jcon is a new, full-featured, Java-based implementation of the Icon programming language. The compiler, written in Icon, generates an intermediate representation that is optimized and then used to produce classfiles of Java bytecode. A four-chunk control-flow model handles goal-directed evaluation and produces constructs not expressible as Java code. The runtime system, written in Java, finds object-oriented programming a great advantage in implementing a dynamically typed language, with method calls replacing many conditional tests. An all-encompassing descriptor class supports values, references, and suspended operations. The procedure call interface is simple and incurs overhead for generator support only when actually needed. Performance is somewhat disappointing, and some limitations are annoying, but in general Java provides a good implementation platform. Copyright © 2000 John Wiley & Sons, Ltd.

A new implementation of the Icon language

Jcon is a new, full-featured, Java-based implementation of the Icon programming language. The compiler, written in Icon, generates an intermediate representation that is optimized and then used to produce classfiles of Java bytecode. A four-chunk control-flow model handles goal-directed evaluation and produces constructs not expressible as Java code. The runtime system, written in Java, finds object-oriented programming a great advantage in implementing a dynamically typed language, with method calls replacing many conditional tests. An all-encompassing descriptor class supports values, references, and suspended operations. The procedure call interface is simple and incurs overhead for generator support only when actually needed. Performance is somewhat disappointing, and some limitations are annoying, but in general Java provides a good implementation platform. Copyright © 2000 John Wiley & Sons, Ltd.

Model for grain boundary sliding and its relevance to optimal structural superplasticity

Abstracthe conclusions reached based on a grain/interphase boundary sliding controlled flow model for optimal structural superplasticity are verified using experimental data from three aluminium alloy systems. Isostructural strain rate–stress relationships could be calculated very accurately using five experimentally determined, physically meaningful constants (three of which could also be calculated from theory; two fully and one partially). The true activation energy for the rate controlling boundary sliding process, the variations of the internal stress distribution arising from sliding, the stress function that is proportional to the measured isostructural isothermal strain rate, and the apparent viscosity, were calculated. It is suggested that the basic units of microscopic boundary sliding in the three aluminium alloys examined have a common structure.MST/3077

Programmers' performance on structured versus nonstructured function definitions

A control-flow model for functional programs is used in an experimental comparison of the performance of programmers on structured versus nonstructured Miranda function definitions. The performance is taken as a measure of the comprehensibility of functional programs. The experimental set-up is similar to the Scanlan study (1989). However, in the present study, a two-factor repeated measures design is used in the statistical analysis. The control-flow model appears to be useful in the shaping of the experiment. A significantly better performance has been found for structured function definitions on both dependent variables: the time needed to answer questions about the function definitions and the proportion correct answers. Moreover, for structured function definitions, a counter-intuitive result has been obtained: there are significantly fewer errors in larger definitions than in smaller ones.

Accurate static estimators for program optimization

Determining the relative execution frequency of program regions is essential for many important optimization techniques, including register allocation, function inlining, and instruction scheduling. Estimates derived from profiling with sample inputs are generally regarded as the most accurate source of this information; static (compile-time) estimates are considered to be distinctly inferior. If static estimates were shown to be competitive, however, their convenience would outweigh minor gains from profiling, and they would provide a sound basis for optimization when profiling is impossible. We use quantitative metrics to compare estimates from static analysis to those derived from profiles. For C programs, simple techniques for predicting branches and loop counts suffice to estimate intraprocedural frequency patterns with high accuracy. To determine inter-procedural estimates successfully, we combine function-level information with a Markov model of control flow over the call graph to produce arc and basic block frequency estimates for the entire program. For a suite of 14 programs, including the C programs from the SPEC92 benchmark suite, we demonstrate that static estimates are competitive with those derived from profiles. Using simple heuristics, we can determine the most frequently executed blocks in each function with 81% accuracy. With the Markov model, we identify 80% of the frequently called functions. Combining the two techniques, we identify 76% of the most frequently executed call sites.

Concurrency extraction via hardware methods executing the static instruction stream

Hardware solutions to low-level (semantic) concurrency extraction are presented, focusing on the reduction of both control-flow and dataflow inhibitors of concurrency in general-purpose and scientific instruction streams. In the first model, CONDEL-1, an input code control flow model based on the code's branch domains is used in the algorithm to detect the reduced procedural dependencies in the input code. This model allows branches to execute concurrently. The cost and delay of the model's concurrency hardware are demonstrated to be relatively low, especially for the detection of concurrency beyond branches. The reduced procedural dependence techniques of CONDEL-1 are combined with high-speed reduced data dependency techniques to yield a machine model, CONDEL-2, executing standard sequential code in a manner beyond data-flow. Simulation results are presented and analyzed, showing the model's functionality and performance improvement. The beneficial effects of limited software optimizations are also reviewed. >

A hybrid scheme for processing data structures in a dataflow environment

The asynchronous nature of the dataflow model of computation allows the exploitation of maximum inherent parallelism in many application programs. However, before the dataflow model of computation can become a viable alternative to the control flow model of computation, one has to find practical solutions to some problems such as efficient handling of data structures. The paper introduces a new model for handling data structures in a dataflow environment. The proposed model combines constant time access capabilities of vectors as well as the flexibility inherent in the concept of pointers. This allows a careful balance between copying and sharing to optimize the storage and processing overhead incurred during the operations on data structures. The mode) is compared by simulation to other data structure models proposed in the literature, and the results are good.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Hybrid structure: data structuring for data flow

The asynchronous nature of the data flow model of computations allows exploitation of maximum inherent parallelism in many application programs. However, before the data flow model of computations can become a viable alternative to the control flow model of computations, one has to find practical solutions to some major problems such as efficient handling of data structures. This article introduces a new model for handling data structures in a data flow environment. The proposed model combines constant time access capabilities of vectors as well as the flexibility inherent in the concept of pointers. This allows a careful balance between copying and sharing to optimize the storage and the processing overhead incurred during the operations on data structures. Using simulation, we present a comparative analysis of our model against other data structure models proposed in literature.

Decentralised control flow - based on UNIX

In the computing science community there is a growing belief that the traditional von Neumann programming model will be superceded in the 1990's by a new decentralised programming model. Various “revolutionary” approaches are being promoted: data flow, reduction, actor and logic models. We propose an alternative “evolutionary” approach, namely a decentralised control flow model. This model, a generalisation of the von Neumann model, can already be recognised as providing the basis of modern operating systems such as UNIX. In this paper we discuss initially the programming of future decentralised computing systems that represent a convergence of computer networks and parallel architectures. Next we describe the decentralised control flow model, and finally we present a simple programming language called BASIX that embodies the model.