Method of Brackets and Feynman diagrams evaluation

In this work we present the relation between method of brackets and the master theorem of Ramanujan in the evaluation of multivariable integrals, in this case Feynman diagrams.Comment: 6 pages, 2 figures. Published in Proc. of 'Loops and Legs in Quantum Field Theory'', April, 2010, W\'orlitz, German

Frontend frequency-voltage adaptation for optimal energy-delay/sup 2/

In this paper, we present a clustered, multiple-clock domain (CMCD) microarchitecture that combines the benefits of both clustering and globally asynchronous locally synchronous (GALS) designs. We also present a mechanism for dynamically adapting the frequency and voltage of the frontend of the CMCD with the goal to optimize the energy-delay/sup 2/ product (ED2P). Our mechanism has minimal hardware cost, is entirely self-adjustable, does not depend on any thresholds, and achieves results close to optimal. We evaluate it on 16 SPEC 2000 applications and report 17.5% ED2P reduction on average (80% of the upper bound).Peer ReviewedPostprint (published version

Virtual-physical registers

A novel dynamic register renaming approach is proposed in this work. The key idea of the novel scheme is to delay the allocation of physical registers until a late stage in the pipeline, instead of doing it in the decode stage as conventional schemes do. In this way, the register pressure is reduced and the processor can exploit more instruction-level parallelism. Delaying the allocation of physical registers require some additional artifact to keep track of dependences. This is achieved by introducing the concept of virtual-physical registers, which do not require any storage location and are used to identify dependences among instructions that have not yet allocated a register to its destination operand. Two alternative allocation strategies have been investigated that differ in the stage where physical registers are allocated: issue or write-back. The experimental evaluation has confirmed the higher performance of the latter alternative. We have performed all evaluation of the novel scheme through a detailed simulation of a dynamically scheduled processor. The results show a significant improvement (e.g., 19% increase in IPC for a machine with 64 physical registers in each file) when compared with the traditional register renaming approach.Peer ReviewedPostprint (published version

Using MCD-DVS for dynamic thermal management performance improvement

With chip temperature being a major hurdle in microprocessor design, techniques to recover the performance loss due to thermal emergency mechanisms are crucial in order to sustain performance growth. Many techniques for power reduction in the past and some on thermal management more recently have contributed to alleviate this problem. Probably the most important thermal control technique is dynamic voltage and frequency scaling (DVS) which allows for almost cubic reduction in power with worst-case performance penalty only linear. So far, DVS techniques for temperature control have been studied at the chip level. Finer grain DVS is feasible if a globally-asynchronous locally-synchronous (GALS) design style is employed. GALS, also known as multiple-clock domain (MCD), allows for an independent voltage and frequency control for each one of the clock domains that are part of the chip. There are several studies on DVS for GALS that aim to improve energy and power efficiency but not temperature. This paper proposes and analyses the usage of DVS at the domain level to control temperature in a clustered MCD microarchitecture with the goal of improving the performance of applications that do not meet the thermal constraints imposed by the designers.Peer ReviewedPostprint (published version

Gauge invariant investigation of the nature of Confinement

We observe a strong correlation between the decrease in the number of action density peaks in SU(2) Yang-Mills configurations with cooling and that of the string tension. The nature and distribution of these peaks is investigated. The relationship with monopole currents after the abelian projection is also considered.Comment: uuencoded and Z-compressed file of the Postcript version of our contribution to LATTICE 95. 4 pages of text and 4 figure

The student evaluation of teaching and the competence of students as evaluators

When the college student satisfaction survey is considered in the promotion and recognition of instructors, a usual complaint is related to the impact that biased ratings have on the arithmetic mean (used as a measure of teaching effectiveness). This is especially significant when the number of students responding to the survey is small. In this work a new methodology, considering student to student perceptions, is presented. Two different estimators of student rating credibility, based on centrality properties of the student social network, are proposed. This method is established on the idea that in the case of on-site higher education, students often know which others are competent in rating the teaching and learning process.Comment: 20 pages, 2 table

Numerical study of the shape and integral parameters of a dendrite

We present a numerical study of sidebranching of a solidifying dendrite by means of a phase--field model. Special attention is paid to the regions far from the tip of the dendrite, where linear theories are no longer valid. Two regions have been distinguished outside the linear region: a first one in which sidebranching is in a competition process and a second one further down where branches behave as independent of each other. The shape of the dendrite and integral parameters characterizing the whole dendrite (contour length and area of the dendrite) have been computed and related to the characteristic tip radius for both surface tension and kinetic dominated dendrites. Conclusions about the different behaviors observed and comparison with available experiments and theoretical predictions are presented.Comment: 10 pages, 7 figures, Accepted for publication in Phys. Rev.

Motivic Milnor fiber of a quasi-ordinary hypersurface

Let f : (Cd+1, 0) -> (C, 0) be a germ of complex analytic function such that its zero level defines an irreducible germ of quasi-ordinary hypersurface (S, 0) subset of (Cd+1, 0). We describe the motivic Igusa zeta function, the motivic Milnor fibre and the Hodge-Steenbrink spectrum of f at 0 in terms of topological invariants of (S, 0) subset of (Cd+1, 0)