On a graph-theoretical model for cyclic register allocation

AbstractIn the process of compiling a computer programme, we consider the problem of allocating variables to registers within a loop. It can be formulated as a coloring problem in a circular arc graph (intersection graph of a family F of intervals on a circle). We consider the meeting graph of F introduced by Eisenbeis, Lelait and Marmol. Proceedings of the Fifth Workshop on Compilers for Parallel Computers, Malaga, June 1995, pp. 502–515. Characterizations of meeting graphs are developed and their basic properties are derived with graph theoretical arguments.Furthermore some properties of the chromatic number for periodic circular arc graphs are derived

Circular-arc Graph Coloring and Unrolling

The register periodic allocation problem is viewed as unrolling and coloring the underlying structure of circular-arc graph. The problem is to find relations between the unrolling degree and the chromatic number. For this purpose we distinguish cyclic colorings that can be found by means of the {\em meeting graph} and non-cyclic ones for which we prove the asymptotic property: let $r$ be the width of the original interval family. Then the $u$-unrolled graph is $r$ or $r+1$-colorable for $u$ large enough

The Meeting Graph : a New Framework for Loop Register Allocation

Projet CHARMERegister allocation is a compiler phase where the gains can be essential in achieving performance on new architectures exploiting instruction level parallelism. We focus our attention on loops and improve the existing methods by introducing a new kind of graph. We model loop unrolling and register allocation together in a common framework, called the {\em meeting graph}. We expect that our results improve significantly loop register allocation while keeping the amount of code replication low. As a byproduct, we present an optimal algorithm for allocating loop variables to a rotating register file, as well as a new heuristic for loop variables spilling

Some aspects on modelling of the β-phase depletion behaviour under different oxide growth kinetics in HVOF CoNiCrAlY coatings

In this paper, β-phase depletion behaviour of free-standing high velocity oxy-fuel (HVOF) thermally sprayed CoNiCrAlY coatings was studied. Microstructural analysis showed a two-phase microstructure of γ-Ni matrix and β-NiAl secondary phase after heat treatment. Fine grains were found around the sprayed particle boundaries and coarse grains were retained as the original particle structure, with grain sizes varying from 2 to 0.5 μm or even less for both phases. The β-phase depletion behaviour was investigated during isothermal oxidation and was also modelled through diffusion calculations. A previously developed β-phase depletion model was utilised to study the evolution of β-phase depletion under different oxide growth kinetics. Three oxide growth models were tried: 1) Meier model, 2) thermogravimetric analysis (TGA) model, and 3) experimentally fitted oxide growth model. The oxide growth kinetics were converted to Al flux functions which were used as the boundary conditions in the DICTRA modelling. It is shown that the results obtained from the three models exhibit good agreements between the measured and predicted results for times up to 100 h at 1100 C, but discrepancies were noted at longer oxidation times. Further improvements on closely modelling the oxidation kinetics and the effective diffusion behaviour are needed to minimise the discrepancies at longer oxidation times

Modelling and experimental study on β-phase depletion behaviour of HVOF sprayed free-standing CoNiCrA1Y coatings during oxidation

This paper investigates the β-phase depletion behaviour during oxidation of free-standing CoNiCrA1Y (Co-31.7%Ni-20.8%Cr-8.1%A1-0.5%Y, all in wt%) bond coats prepared by high velocity oxy-fuel (HVOF) thermal spraying. The microstructure of the coatings was characterised using scanning electron microscopy with energy dispersive X-ray (EDX) analysis and electron backscatter diffraction (EBSD). It comprises a two phase structure of fcc γ-Ni and bcc β-NiA1, with grain sizes varying largely from 0.5 to 2 μm for both phases. Isothermal oxidation tests of the free-standing coatings were carried out at 1100 °C for times up to 250 h. The β phase depletion behaviour at the surface was measured and was also simulated using Thermo-Calc and DICTRA software. An A1 flux function derived from an oxide growth model was employed as the boundary condition in the diffusion model. The diffusion calculations were performed using the TTNi7 thermodynamic database together with the MOB2 mobility database. Reasonable agreement was achieved between the measured and the predicted element concentration and phase fraction profiles after various time periods. Grain boundary diffusion is likely to be important to element diffusion in this HVOF sprayed CoNiCrA1Y coating due to the sub-micron grains

Les expulsés allemands. Des victimes en quête de reconnaissance

Le débat sur le passé national-socialiste est récurrent en Allemagne de l’Ouest depuis 1945. Il connaît ces dernières années un tournant déclenché notamment par des publications scientifiques ou littéraires. En effet, le pays redécouvre qu’il n’a pas été seulement celui des bourreaux, mais aussi celui de victimes. Parmi elles, on compte notamment les millions de personnes expulsées des territoires allemands de l’Est et d’Europe centrale et orientale. Le pays a largement reconnu le statut de victime de cette population tant sur le plan législatif que sur le plan politique. Ceux-ci ont pourtant surenchéri en considérant d’emblée l’expulsion comme crime contre l’humanité, afin de faire valoir des revendications territoriales de moins en moins avouables au fil du temps. Ils ont par ailleurs entretenu cette image de victime et de souffrance de diverses manières dans le domaine culturel. Ils ont enfin utilisé le débat de ces dernières années et la compassion de leurs compatriotes vis-à-vis des expulsés de Yougoslavie et du Kosovo pour retrouver grâce aux yeux de l’opinion publique. Celle-ci trouve toutefois ses limites dans la confrontation récente de deux expositions A Berlin, qui témoignent de deux conceptions différentes de l’histoire.<br>Desde 1945, el debate sobre el pasado nacionalsocialista es recurrente en Alemania del Oeste. Actualmente, está evolucionando gracias a publicaciones históricas y literarias. Efectivamente, Alemania descubre que no fue solamente un país de verdugos sino también de víctimas. Entre ellas están los millones de personas expulsadas de los territorios alemanes del este, de Europa central y oriental. El país reconoció ampliamente el estatuto de víctima de esta población, tanto desde el punto de vista legislativo como político. Sin embargo, sus representantes han sobrepujado de entrada al considerar la expulsión como un crimen contra la humanidad, para que se tome en cuenta sus reivindicaciones territoriales. Por otra parte, han mantenido a nivel cultural esta imagen de víctima y de sufrimiento de diferentes maneras. Por fin, han instrumentalizado la compasión de sus compatriotas y el debate de estos últimos años sobre los expulsados de Yugoslavia y del Kosovo para granjearse la simpatía de la opinión pública. Sin embargo, esta estrategia alcanza sus límites como lo demuestran dos recientes exposiciones, que subrayan dos concepciones diferentes de la historia.<br>The debate on West Germany national-socialist past is recurrent since 1945. Lately, it has reached a turning point essentially because of some scientific and literary publications. The country discovers again that it was not only the country of the executioners, but also a country of victims. Among them, there were particularly billion of people, who got expelled both from the Eastern German territories, and Eastern and Central Europe. The country largely recognized the victime status of this population on a legislative and political level. But those people bid higher, considering that expulsion was a crime against humanity, in order to put forward territorial revendications, which are less and less acceptable. This image of victim and suffering has been nourished in different ways on the cultural level. And they enventually used their compatriots’compassion regarding the expellees from Yougoslavia and Kosovo, to re-gain favour in public opinion. However this phenomenon is limited, as it could be seen through the confrontation of two exhibitions in Berlin, which both represented two different conceptions of history

Un "nationalisme" des réfugiés en République fédérale d'Allemagne ? : l'exemple de l'Association provinciale de Silésie et de l'Association provinciale des Hauts-Silésiens

Since their creation in 1950 by Silesians expelled from the Heimat in 1945, the Provincial Association of Silesia (LS) and the Provincial Association of the Upper Silesians (LdO) have developed political, cultural activities. Accused to be nationalist and excluded by Germany where the notion of nation is taboo, they have tried to prepare the retur of Silesians to their Heimat and have worked for a better integration of their members in the West German society. This study deals with the actions and discourses of the two associations on federal and local level. The gap is growing between leaders and members, who have resigned. Their major demand, recovery of Silesia, may be assimilated to demands of the extremists, but the demand of the Silesian refugees is less caused by the expression of ideology than the one of a psychological lack : we could then call it an "emotional nationalism".Crées en 1950 par les Silésiens expulsés de leur Heimat en 1945, l'Association provinciale de Silésie (LS) et l'Association provinciale des Hauts-Silésiens (LdO) développent des activités politiques, culturelles et sociales. Accusées d'être nationalistes et frappées d'ostracisme dans cette Allemagne où la " nation " est taboue, elles tentent de préparer le retour des Silésiens dans leur Heimat et oeuvrent en faveur d'une meilleure intégration de leurs adhérents dans la société ouest-allemande. Cette étude concerne les actions et les discours des deux organisations au niveau fédéral et local. Le fossé se creuse entre les dirigeants et les adhérents, qui se résignent. Si leur revendication majeure, le recouvrement de la Silésie, peut être assimilée aux revendications des partis d'extrême-droite, la demande des réfugiés silésiens est pourtant moins le fait d'une idéologie que d'un vide psychologique : on pourrait parler de " nationalisme affectif "

Etude microstructurale fine de revetements ceramiques de type barriere thermique; incidence sur la resistance thermomecanique de ces revetements

SIGLEAvailable from INIST (FR), Document Supply Service, under shelf-number : TD 81035 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc

Compilation Techniques for Multimedia Processors

The huge processing power needed by multimedia applications has led to multimedia extensions in the instruction set of microprocessors which exploit subword parallelism. Examples of these extended instruction sets are the Visual Instruction Set of the UltraSPARC processor, the AltiVec instruction set of the PowerPC processor, the MMX and ISS extensions of the Pentium processors, and the MAX-2 instruction set of the HP PA-RISC processor. Currently, these extensions can only be used by programs written in assembly language, through system libraries or by calling specialized macros in a high-level language. Therefore, these instructions are not used by most applications. We propose two code generation techniques to produce native code using these multimedia extensions for programs written in a high level language: classical vectorization and vectorization by unrolling. Vectorization by unrolling is simpler than classical vectorization since data dependence analysis is reduced to acyclic control flow graph analysis. Furthermore, we address the problem of unaligned memory accesses. This can be handled by both static analysis and dynamic run time checking. Preliminary experimental results for a code generator for the UltraSPARC VIS instruction set show that speedups of up to a factor of 4.8 are possible, and that vectorization by unrolling is much simpler but as effective as classical vectorization. Keywords compiler, multimedia processors, vectorization, loop unrolling 1