Emulation of a Complex Instruction Set Computer with a Reduced Instruction Set Computer

This paper analyzes some of the difficulties of emulating a Complex Instruction Set Computer (CISC) with a Reduced Instruction Set Computer (RISC). It will be shown that although the speed advantage of a RISC is sacrificed, a CISC can be emulated with the exception of software constructs that support nonstandard hardware interfaces. Some concrete examples will be used to help illustrate the execution- time bottlenecks as well as to discuss possible solutions from an architectural point of view for both Silicon and Gallium Arsenide (GaAs). In addition, it will be shown that the most efficient method of emulation involves debugging compiled High-Level Language (HLL) source code on a CISC, and then recompiling the HLL code with a compiler that is familiar with the target RISC architectur

Integration of Uncertain Ramp Area Aircraft Trajectories and Generation of Optimal Taxiway Schedules at Charlotte Douglas (CLT) Airport

The integration of aircraft maneuver characteristics into an optimal taxiway scheduling solution is challenging due to the uncertainties that are intrinsic to ramp area aircraft trajectories. To address the challenge, we build a stochastic model of ramp area aircraft trajectories that is used to generate a probabilistic measure of conflict within the Charlotte Douglas International Airport (CLT) ramp area. Parameters of the conflict distributions are estimated and passed to a Mixed Integer Linear Program that solves for an optimal taxiway schedule constrained to be conflict free in the presence of trajectory uncertainties. Here we extend our previous research by accounting for departing and arriving aircraft whereas our prior formulation only accounted for departing aircraft

Increasing the Reliability of Software Timing Analysis for Cache-Based Processors

Real-time systems are witnessing a significant increase in critical software's size, complexity, and performance needs, which can only be satisfied with high-performance hardware features. Cache memories, pervasively used to improve average performance, complicate Worst-Case Execution Time analysis: cache placement (i.e., how software objects are mapped to cache) during the testing phase does not only critically affect the observed performance, but also proves to be arduous to control and preserve up to operation. The probabilistic variant of Measurement-Based Timing Analysis (MBPTA) responds to this challenge by deploying time-randomized caches that naturally explore a different random cache placement in each run, relieving the user from producing tests that intercept relevant Cache Conflict Placements (CCP). Yet, to meet an adequate probabilistic CCP coverage, the user is required to collect a minimum number of measurements. We present two mechanisms, CCP-RM and CCP-HRP, to identify CCP with relevant probability of occurrence and large impact on execution-time, for the random modulo (RM) and hash-based random placement (HRP) policies. CCP-RM and CCP-HRP enable a reliable application of MBPTA by computing the number of runs $R^{\prime }$R' necessary to meet the desired CCP coverage. We exhaustively evaluate CCP-RM and CCP-HRP, showing their effectiveness on well-known benchmarks and a railway case study, on top of an accurate simulator and a concrete RTL implementation.This work has received funding from the Spanish Ministry of Science and Innovation under grant TIN2015-65316-P and the HiPEAC Network of Excellence. The Ministry of Economy and Competitiveness partially supported Suzana Milutinovic under FPI grant (BES-2016-077561), Jaume Abella under Ramon y Cajal postdoctoral fellowship (RYC-2013-14717) and Enrico Mezzetti under Juan de la Cierva-Incorporación postdoctoral fellowship (IJCI-2016-27396).Peer ReviewedPostprint (author's final draft

On uses of extreme value theory fit for industrial-quality WCET analysis

Over the last few years, considerable interest has arisen in measurement-based probabilistic timing analysis. The term MBPTA has been used to indistinctly refer to a variety of different applications of Extreme Value Theory (EVT) to the timing analysis problem. The successful application of MBPTA techniques to a score of case studies has not fully dispelled the concerns that industrial stakeholders had with the quality of the computed bounds, hence ultimately with their industrial viability. Placing focus on the MBPTA methods and techniques developed in the PROARTIS and PROXIMA projects, collectively referred to as proMBPTA, we discuss the main misconceptions and pitfalls that can prevent a sound application of EVT-based WCET analysis. Using a combination of arguments and support examples, we show that proMBPTA is a rigorous process, fully amenable to sound and sustainable industrial use.This work has been partially supported by the Spanish Ministry of Economy and Competitiveness (MINECO) under grant TIN2015-65316-P and the HiPEAC Network of Excellence. Jaume Abella has been partially supported by the MINECO under Ramon y Cajal grant RYC-2013-14717. Authors also thank George Lima for his feedback on this manuscript.Peer ReviewedPostprint (author's final draft

Closed Orbit Analysis for RHIC

This report describes Closed Orbit Analysis for RHIC

First Turn Around Strategy for RHIC

We present a strategy for achieving the so-called first turn around in RHIC. The strategy is based on the same method we had proposed to correct a distorted closed orbit in RHIC, i.e., on a generalization of the local three-bump method. We found out that the method is very effective in passing the beam through a non-ideal, insufficiently known, machine. We tested that software on ten different Gaussian distributions of dominant orbit distorting lattice imperfections. The perturbed lattice was generated by the code PATRIS, which was also adapted to control the newly developed software. In all of the ten distributions the software was capable of passing the beam through in 2--3 injection attempts, at full sextupole strength. It was also determined that once the beam makes the first turn around and all the correctors are energized, it stays in the machine for at least several hundred turns that we had checked. The quality of the orbit, that was established in this way, was also found to be very good, i.e., the residual distortions at the places of large beta function were much less than one millimeter. With one or two monitors/correctors broken, the software established a first turn around without any extra difficulties. The quality of such orbit was, of course, somewhat degraded, especially around the broken devices. It was also observed that, in the process of actual closing, the beam develops free betatron oscillations in the amplitude range of 1--5 mm, which can be reduced either by changing the injection conditions to better match the actual closed orbit or by an appropriate damping device. The hardware proposed for RHIC is more than sufficient to meet the demands of the first turn controlling software. The maximum kick angle to be applied to the beam would require less than 2/3 of the corrector's top strength even at the top magnetic rigidity B{rho} = 850 T{center dot}m, which means that the correctors will be performing an easy task at injection

Comparison of Accelerator Codes for a RHIC Lattice

We present the results of comparisons of performances of several tracking or/and analysis codes. The basic purpose of this program was to assess reliability and accuracy of these codes, i.e. to determine the so-called "error bars" for the predicted values of tunes and other lattice functions as a minimum and, if possible, to discover potential difficulties with underlying physical models in these codes, inadequate algorithms, residual bugs and the like. Not only we have been able to determine the error bars, which for instance for the tunes at dp/p = +1% are Δv$sub x$ = 0.0027, Δv$sub y$ = 0.0010, but also our program has brought about improvements of several codes

Analysis of effects of closed orbit errors, quadrupole: Random errors and random quadrupole rotation errors for the SSC LEB

This report talks about the Analysis of effects of closed orbit errors, quadrupole: Random errors and random quadrupole rotation errors for the SSC LE