A5048744223- Parallel Computing and Optimization Techniques
- Stellar, planetary, and galactic studies
- Astronomy and Astrophysical Research
- Logic, programming, and type systems
- Astronomical Observations and Instrumentation
- Software Testing and Debugging Techniques
- Distributed and Parallel Computing Systems
- Astro and Planetary Science
- Software System Performance and Reliability
- Radiation Effects in Electronics
- Astrophysics and Star Formation Studies
- Distributed systems and fault tolerance
- Embedded Systems Design Techniques
- Astrophysical Phenomena and Observations
- Adaptive optics and wavefront sensing
- Software Engineering Research
- Advanced Software Engineering Methodologies
- Advanced Data Storage Technologies
- Galaxies: Formation, Evolution, Phenomena
- Formal Methods in Verification
- Calibration and Measurement Techniques
- Solar and Space Plasma Dynamics
- Teaching and Learning Programming
- Software Reliability and Analysis Research
- Matrix Theory and Algorithms
Haverford College
2003-2023
Grinnell College
2017
University of Illinois Urbana-Champaign
2011
Rutgers, The State University of New Jersey
2004-2005
University College London
1989-2000
University of Maryland, College Park
1992-1996
UCL Australia
1995
Rutherford Appleton Laboratory
1992-1994
The first all-sky survey for cosmic sources of extreme-ultraviolet radiation has been carried out with the UK Wide Field Camera on ROSAT. A reduction data yielded a catalogue 383 relatively bright EUV sources, forming WFC Bright Source Catalogue. This represents 30-fold increase in number astrophysical objects detected ~ 60–200 eV energy band and covers flux range, each two bands, more than 2000. search (typically 1-arcmin) error circles using variety catalogues SIMBAD base, identified...
Array data dependence analysis methods currently in use generate false dependences that can prevent useful program transformations. These arise because the questions asked are conservative approximations to we really should be asking. Unfortunately, asking go beyond integer programming and require decision procedures for a sublcass of Presburger formulas. In this paper, describe how extend Omega test so it answer these queries allow us eliminate dependences. We have implemented techniques...
Time skewing is a compile-time optimization that can provide arbitrarily high cache hit rates for class of iterative calculations, given sufficient number time steps and memory. Thus, it eliminate processor idle caused by inadequate main memory bandwidth. In this article, we give generalization multiprocessor architectures, discuss multilevel caches. Our multiprocessors lets us any combination bandwidth, limited network latency, sufficiently large problem cache. As in the uniprocessor case,...
Traditional array dependence analysis, which detects potential memory aliasing of references is a key analysis technique for automatic parallelization. Recent studies benchmark codes indicate that limitations cause many compilers to overlook large amounts parallelism, and exploiting this parallelism requires algorithms answer new question about references, not just get better answers the old questions aliasing. We need ask flow values in arrays, check legality privatization, conditions under...
We describe the ROSAT International X-ray/Optical Survey (RIXOS), a medium-sensitivity survey and optical identification of X-ray sources discovered in high Galactic latitude fields (|b|>28°) observed with Position Sensitive Proportional Counter (PSPC) detector. The made use central 17 arcmin each field. A flux limit 3×10−14 erg cm−2 s−1 (0.5–2 keV) was adopted for survey, minimum exposure time 8000 s required qualifying observations. are therefore substantially above detection threshold...
Should we say something
This paper presents a new compile-time analysis that enables testing methodology for white-box coverage of error recovery code (i.e., exception handlers) in Java web services using compiler-directed fault injection. The allows compiler-generated instrumentation to guide the injection and record exercised. (An injected is experienced as exception.) (i) identifies exception-flow 'def-uses' be tested this manner, (ii) determines kind requested at program point, (iii) finds appropriate locations...
Stencil computations figure prominently in the core kernels of many scientific computations, such as partial differential equation solvers. Parallel scaling stencil can be significantly improved on multicore processors using advanced tiling techniques that include time dimension, diamond tiling. Such are difficult to general purpose optimizing compilers because need for inter-procedural pointer and array data-flow analysis, plus tune scheduling strategies tile size parameters each pairing...
Existing compilers often fail to parallelize sequential code, even when a program can be manually transformed into parallel form by sequence of well-understood transformations (as in the case for many Perfect Club Benchmark programs). These failures occur several reasons: code implemented compiler may not sufficient produce find proper transformations, or able prove that one necessary is legal. When fails extract parallelism from program, programmer try additional parallelism. Unfortunately,...
Array data dependence analysis methods currently in use generate false dependences that can prevent useful program transformations. These arise because the questions asked are conservative approximations to we really should be asking. Unfortunately, asking go beyond integer programming and require decision procedures for a subclass of Presburger formulas. In this paper, describe how extend Omega test so it answer these queries allow us eliminate dependences. We have implemented techniques...
The system IK Peg has been known to be a binary for over 60 years but the secondary never identified. detection of this in British Wide Field Camera All-Sky Survey EUV enabled positively identified as white dwarf. Fits survey data, first IUE spectrum, and archival X-ray data indicate that contains high-mass(~1 M⊙) dwarf it is very close edge-on. evolutionary status discussed; shown result common-envelope phase, expected evolve into Type I supernova or cataclysmic variable.
A number of new non-interacting binary systems comprising a white dwarf plus normal stellar companion have been discovered by the ROSAT X-ray and EUV sky surveys. We discuss identification nine these objects, determine temperatures gravities dwarfs, compare their atmospheric compositions with population isolated dwarfs. As result, it may be possible to estimate how many hot dwarfs in total reside systems. Coronal emission is detected several systems, its nature, light likely age binaries,...
A 73-ks pointed ROSAT observation revealed the RS CVn system HR 5110 to be in an outburst lasting over 3 d. Although rise was not observed, this 3-d period PSPC count rate decayed one-half of its initial value, which itself some 4–5 times larger than all-sky survey value. The for simultaneous WFC observations remained virtually constant throughout pointing but about a factor 3.6 higher value during survey. Calculations based on spectral parameters show that simple flare mechanism and...
Optical identifications for 195 EUV sources located in the ROSAT Wide Field Camera all-sky survey are presented. We list 69 previously unknown EUV-emitting white dwarfs, 114 active stars, 7 new magnetic cataclysmic variables and 5 galaxies. Several of dwarfs have resolved M-type companions, while five unresolved dwarf/M-star pairs. Finding charts given optical counterparts.
Array data dependence analysis methods currently in use generate false dependences that can prevent useful program transformations. These arise because the questions asked are conservative approximations to we really should be asking. Unfortunately, asking go beyond integer programming and require decision procedures for a sublcass of Presburger formulas. In this paper, describe how extend Omega test so it answer these queries allow us eliminate dependences. We have implemented techniques...
We present a new approach that uses compiler- directed fault-injection for coverage testing of recovery code in Internet services to evaluate their robustness op- erating system and I/O hardware faults. define set program-fault metrics enable quantifica- tion Java catch blocks exercised during experiments. use compiler analyses instrument appli- cation two ways: direct fault injection occur at appropriate points execution, measure the resulting coverage. As proof concept these ideas, we have...
We present results of an extensive study the X-ray spectral properties sources detected in RIXOS survey, which is a large, nearly complete sample objects serendipitously ROSAT PSPC fields down to flux limit 3×10−14 erg cm−2 s−1 (0.5–2 keV). show that for surveys containing with low count rate, such as RIXOS, slopes estimated using simple hardness ratios band can be biased. Instead, we analyse three-colour data statistical techniques appropriate Poisson regime remove effects this bias. also...