13 research outputs found
A quantitative charcterization of control flow context: software measures for programming environments
A review of published measures of control flow complexity in programs reveals three major deficiencies: loss of information, lack of specificity, and lack of analytical support. A new approach is used to characterize the control structure of a program, with the aim of defining properties and measures of control flow that can be of immediate use to programmers, regardless of their utility as complexity measures. Mathematical rigor and analytical evaluation techniques are used to define a set of properties of control structure and a corresponding vector of measures. Instead of defining the properties and measures for an entire flowgraph, they are defined at the node level, reflecting the control flow surrounding each node in a flowgraph. The properties and their measures reflect the following characteristics of control flow: nesting, iteration, structuredness, and predecessors. Algorithms for computing the properties and their measures are presented. An assessment of the computational complexity of the algorithms shows that they are feasible programming environment tools;A finite path set, representing all possible execution sequences, is evaluated as a characterizing property. Desired characteristics of the path set are defined and used to evaluate four published path subset criteria. Those criteria are shown to be deficient, so a fifth criterion is defined. However, the path set satisfying this fifth criterion is shown to be too large to be of practical use to a programmer
Proceedings of the 1968 Summer Institute on Symbolic Mathematical Computation
Investigating symbolic mathematical computation using PL/1 FORMAC batch system and Scope FORMAC interactive syste
Programmiersprachen und Rechenkonzepte
Seit 1984 veranstaltet die GI-Fachgruppe "Programmiersprachen und Rechenkonzepte", die aus den ehemaligen Fachgruppen 2.1.3 "Implementierung von Programmiersprachen" und 2.1.4 "Alternative Konzepte für Sprachen und Rechner" hervorgegangen ist, regelmäßig im Frühjahr einen Workshop im Physikzentrum Bad Honnef. Das Treffen dient in erster Linie dem gegenseitigen Kennenlernen, dem Erfahrungsaustausch, der Diskussion und der Vertiefung gegenseitiger Kontakte
IST Austria Thesis
Motivated by the analysis of highly dynamic message-passing systems, i.e. unbounded thread creation, mobility, etc. we present a framework for the analysis of depth-bounded systems. Depth-bounded systems are one of the most expressive known fragment of the π-calculus for which interesting verification problems are still decidable. Even though they are infinite state systems depth-bounded systems are well-structured, thus can be analyzed algorithmically. We give an interpretation of depth-bounded systems as graph-rewriting systems. This gives more flexibility and ease of use to apply depth-bounded systems to other type of systems like shared memory concurrency.
First, we develop an adequate domain of limits for depth-bounded systems, a prerequisite for the effective representation of downward-closed sets. Downward-closed sets are needed by forward saturation-based algorithms to represent potentially infinite sets of states. Then, we present an abstract interpretation framework to compute the covering set of well-structured transition systems. Because, in general, the covering set is not computable, our abstraction over-approximates the actual covering set. Our abstraction captures the essence of acceleration based-algorithms while giving up enough precision to ensure convergence. We have implemented the analysis in the PICASSO tool and show that it is accurate in practice. Finally, we build some further analyses like termination using the covering set as starting point
Foundations of Software Science and Computation Structures
This open access book constitutes the proceedings of the 23rd International Conference on Foundations of Software Science and Computational Structures, FOSSACS 2020, which took place in Dublin, Ireland, in April 2020, and was held as Part of the European Joint Conferences on Theory and Practice of Software, ETAPS 2020. The 31 regular papers presented in this volume were carefully reviewed and selected from 98 submissions. The papers cover topics such as categorical models and logics; language theory, automata, and games; modal, spatial, and temporal logics; type theory and proof theory; concurrency theory and process calculi; rewriting theory; semantics of programming languages; program analysis, correctness, transformation, and verification; logics of programming; software specification and refinement; models of concurrent, reactive, stochastic, distributed, hybrid, and mobile systems; emerging models of computation; logical aspects of computational complexity; models of software security; and logical foundations of data bases.
Optimal Global Instruction Scheduling for the Itanium® Processor Architecture
On the Itanium 2 processor, effective global instruction scheduling is crucial to high performance. At the same time, it poses a challenge to the compiler: This code generation subtask involves strongly interdependent decisions and complex trade-offs that are difficult to cope with for heuristics. We tackle this NP-complete problem with integer linear programming (ILP), a search-based method that yields provably optimal results. This promises faster code as well as insights into the potential of the architecture. Our ILP model comprises global code motion with compensation copies, predication, and Itanium-specific features like control/data speculation. In integer linear programming, well-structured models are the key to acceptable solution times. The feasible solutions of an ILP are represented by integer points inside a polytope. If all vertices of this polytope are integral, then the ILP can be solved in polynomial time. We define two subproblems of global scheduling in which some constraint classes are omitted and show that the corresponding two subpolytopes of our ILP model are integral and polynomial sized. This substantiates that the found model is of high efficiency, which is also confirmed by the reasonable solution times. The ILP formulation is extended by further transformations like cyclic code motion, which moves instructions upwards out of a loop, circularly in the opposite direction of the loop backedges. Since the architecture requires instructions to be encoded in fixed-sized bundles of three, a bundler is developed that computes bundle sequences of minimal size by means of precomputed results and dynamic programming. Experiments have been conducted with a postpass tool that implements the ILP scheduler. It parses assembly procedures generated by Intel�s Itanium compiler and reschedules them as a whole. Using this tool, we optimize a selection of hot functions from the SPECint 2000 benchmark. The results show a significant speedup over the original code.Globale Instruktionsanordnung hat beim Itanium-2-Prozessor großen
Einfluß auf die Leistung und stellt dabei gleichzeitig eine Herausforderung
für den Compiler dar: Sie ist mit zahlreichen komplexen, wechselseitig
voneinander abhängigen Entscheidungen verbunden, die für Heuristiken
nur schwer zu beherrschen sind.Wir lösen diesesNP-vollständige
Problem mit ganzzahliger linearer Programmierung (ILP), einer suchbasierten
Methode mit beweisbar optimalen Ergebnissen. Das ermöglicht
neben schnellerem Code auch Einblicke in das Potential der Itanium-
Prozessorarchitektur. Unser ILP-Modell umfaßt globale Codeverschiebungen
mit Kompensationscode, Prädikation und Itanium-spezifische
Techniken wie Kontroll- und Datenspekulation.
Bei ganzzahliger linearer Programmierung sind wohlstrukturierte
Modelle der Schlüssel zu akzeptablen Lösungszeiten. Die zulässigen Lösungen
eines ILPs werden durch ganzzahlige Punkte innerhalb eines
Polytops repräsentiert. Sind die Eckpunkte dieses Polytops ganzzahlig,
kann das ILP in Polynomialzeit gelöst werden. Wir definieren zwei Teilprobleme
globaler Instruktionsanordnung durch Auslassung bestimmter
Klassen von Nebenbedingungen und beweisen, daß die korrespondierenden
Teilpolytope unseres ILP-Modells ganzzahlig und von polynomieller
Größe sind. Dies untermauert die hohe Effizienz des gefundenen Modells,
die auch durch moderate Lösungszeiten bestätigt wird.
Das ILP-Modell wird um weitere Transformationen wie zyklische Codeverschiebung
erweitert; letztere bezeichnet das Verschieben von Befehlen
aufwärts aus einer Schleife heraus, in Gegenrichtung ihrer Rückwärtskanten.
Da die Architektur eine Kodierung der Befehle in Dreierbündeln
fester Größe vorschreibt, wird ein Bundler entwickelt, der Bündelsequenzen
minimaler Länge mit Hilfe vorberechneter Teilergebnisse und dynamischer
Programmierung erzeugt.
Für die Experimente wurde ein Postpassoptimierer erstellt. Er liest
von Intels Itanium-Compiler erzeugte Assemblerroutinen ein und ordnet
die enthaltenen Instruktionen mit Hilfe der ILP-Methode neu an. Angewandt
auf eine Auswahl von Funktionen aus dem Benchmark SPECint
2000 erreicht der Optimierer eine signifikante Beschleunigung gegenüber
dem Originalcode