Performance Analysis of and Tool Support for Transactional Memory on BG/Q

Martin Schindewolf worked during his internship at the Lawrence Livermore National Laboratory (LLNL) under the guidance of Martin Schulz at the Computer Science Group of the Center for Applied Scientific Computing. We studied the performance of the TM subsystem of BG/Q as well as researched the possibilities for tool support for TM. To study the performance, we run CLOMP-TM. CLOMP-TM is a benchmark designed for the purpose to quantify the overhead of OpenMP and compare different synchronization primitives. To advance CLOMP-TM, we added Message Passing Interface (MPI) routines for a hybrid parallelization. This enables to run multiple MPI tasks, each running OpenMP, on one node. With these enhancements, a beneficial MPI task to OpenMP thread ratio is determined. Further, the synchronization primitives are ranked as a function of the application characteristics. To demonstrate the usefulness of these results, we investigate a real Monte Carlo simulation called Monte Carlo Benchmark (MCB). Applying the lessons learned yields the best task to thread ratio. Further, we were able to tune the synchronization by transactifying the MCB. Further, we develop tools that capture the performance of the TM run time system and present it to the application's developer. The performance of the TM run time system relies on the built-in statistics. These tools use the Blue Gene Performance Monitoring (BGPM) interface to correlate the statistics from the TM run time system with performance counter values. This combination provides detailed insights in the run time behavior of the application and enables to track down the cause of degraded performance. Further, one tool has been implemented that separates the performance counters in three categories: Successful Speculation, Unsuccessful Speculation and No Speculation. All of the tools are crafted around IBM's xlc compiler for C and C++ and have been run and tested on a Q32 early access system

A new HW Vir binary from the Palomar Transient Factory: PTF1 J072455.75+125300.3 - An eclipsing subdwarf B binary with a M-star companion

We report the discovery of an eclipsing binary -- PTF1 J072456$+$125301-- composed of a subdwarf B (sdB) star ($g'=17.2^m$) with a faint companion. Subdwarf B stars are core helium-burning stars, which can be found on the extreme horizontal branch. About half of them reside in close binary systems, but few are known to be eclipsing, for which fundamental stellar parameters can be derived.\newline We conducted an analysis of photometric data and spectra from the Palomar 60'' and the 200" Hale telescope respectively. A quantitative spectral analysis found an effective temperature of $T_{\text{eff}}=33900\pm350$\,K, log g = $5.74\pm0.08$ and log($n_{\text{He}}/n_{\text{H}}) = -2.02 \pm0.07$, typical for an sdB star. The companion does not contribute to the optical light of the system, except through a distinct reflection effect. From the light curve an orbital period of 0.09980(25)\,d and a system inclination of 83.56\pm0.30\,^{\circ} were derived. The radial velocity curve yielded an orbital semi-amplitude of K_1=95.8\pm 8.1\,\text{km s^{-1}}. The mass for the M-type dwarf companion is $0.155\pm0.020\,M_{\odot}$. PTF1\,J072456$+$125301 has similar atmospheric parameters to those of pulsating sdB stars (V346 Hya stars). Therefore it could be a high-priority object for asteroseismology, if pulsations were detected such as in the enigmatic case of NY Vir.Comment: Accepted to A&A, 7pages, 4 figure

The rhodium, silver and indium content of some chondritic meteorites

By neutron activation analysis the rhodium, silver and indium content of five chondritic meteorites has been determined. The average data are 0.186 and 0.094 p.p.m. for rhodium and silver. The upper limit for the indium content is 0.001 p.p.m. The values for rhodium and silver are in fair agreement with the data estimated by and ; the indium values, however, are lower by a factor of 100 or more.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/32432/1/0000514.pd

A quantitative NLTE analysis of visual and ultraviolet spectra of four helium-rich subdwarf O stars

Aims. Hot subdwarf stars represent a poorly understood late phase of stellar evolution. While binary evolution plays an important role for the formation of B-Type subdwarfs (sdB), the origin of the helium dominated subclass of O-Type subdwarfs (He-sdO) is still unknown. We search for chemical signatures of their genesis by means of quantitative spectral analyses of high-quality visual and ultraviolet spectra. Methods. Four prototypical He-sdO stars, one belonging to the nitrogen-rich and three to the C-rich subclass, were selected for which archival far-ultraviolet spectra from the FUSE satellite as well as high-resolution visual and UVA spectra taken with the ESO-UVES/FEROS spectrographs are available. Using TLUSTY200/SYNSPEC49 to compute line blanketed-non-local thermodynamic equilibrium (NLTE) model atmospheres and synthetic spectra, atmospheric parameters and the abundances patterns have been derived. The final models included H, He, C, N, O, Ne, Mg, Al, Si, P, S, Fe, and Ni represented by the most detailed model atoms available. Because of the enrichment of either nitrogen or carbon, it turned out, that models including these elements at the appropriate high abundance provide sufficiently accurate approximations to the temperature stratification of full models. Results. No indications for binarity were found, neither radial velocity variations nor photometric evidence for the presence of a companion could be detected. All stars have helium-dominated atmospheres almost free of hydrogen and temperatures between 42 000 K and 47 000 K while their surface gravities lie between log g = 5.4 and 5.7. The abundance pattern of CD-31°4800 displays the signatures of CNO burning, while heavier elements are subsolar by about 0.4 dex, except for Ne and Si which are close to solar. The abundance patterns of the C-rich He-sdOs are more complex. A slightly subsolar metallicity is accompanied by N-enrichment and O-deficiency, less pronounced than in CD-31°4800. Neon is mildly to strongly enriched, up to a factor of ten with respect to the sun in LS IV + 10° 9. The nickel-to-iron ratio is significantly super-solar. Using spectral energy distributions and Gaia parallaxes the masses of the stars were determined. They are found to scatter around the canonical mass for the core helium flash, although the uncertainties are large. Conclusions. The abundance pattern observed for CD-31°4800 is consistent with predictions of models for slow (cold) mergers of pairs of equal mass helium WDs except for the low oxygen abundance observed. Models for composite mergers were considered for the C-rich stars, but predict abundance pattern dissimilar to those determined. [CW83] 0904-02, though, may be a candidate for a composite He-WD merger, as it rotates and appears to be more massive than the other program stars. New evolutionary models for the hot flasher scenario predict abundance patterns similar to those determined for the C-rich stars. Hence, C-rich He-sdO may well result from late He flashes with deep-mixing episodes.Facultad de Ciencias Astronómicas y GeofísicasInstituto de Astrofísica de La Plat

A quantitative NLTE analysis of visual and ultraviolet spectra of four helium-rich subdwarf O stars

Aims. Hot subdwarf stars represent a poorly understood late phase of stellar evolution. While binary evolution plays an important role for the formation of B-Type subdwarfs (sdB), the origin of the helium dominated subclass of O-Type subdwarfs (He-sdO) is still unknown. We search for chemical signatures of their genesis by means of quantitative spectral analyses of high-quality visual and ultraviolet spectra. Methods. Four prototypical He-sdO stars, one belonging to the nitrogen-rich and three to the C-rich subclass, were selected for which archival far-ultraviolet spectra from the FUSE satellite as well as high-resolution visual and UVA spectra taken with the ESO-UVES/FEROS spectrographs are available. Using TLUSTY200/SYNSPEC49 to compute line blanketed-non-local thermodynamic equilibrium (NLTE) model atmospheres and synthetic spectra, atmospheric parameters and the abundances patterns have been derived. The final models included H, He, C, N, O, Ne, Mg, Al, Si, P, S, Fe, and Ni represented by the most detailed model atoms available. Because of the enrichment of either nitrogen or carbon, it turned out, that models including these elements at the appropriate high abundance provide sufficiently accurate approximations to the temperature stratification of full models. Results. No indications for binarity were found, neither radial velocity variations nor photometric evidence for the presence of a companion could be detected. All stars have helium-dominated atmospheres almost free of hydrogen and temperatures between 42 000 K and 47 000 K while their surface gravities lie between log g = 5.4 and 5.7. The abundance pattern of CD-31°4800 displays the signatures of CNO burning, while heavier elements are subsolar by about 0.4 dex, except for Ne and Si which are close to solar. The abundance patterns of the C-rich He-sdOs are more complex. A slightly subsolar metallicity is accompanied by N-enrichment and O-deficiency, less pronounced than in CD-31°4800. Neon is mildly to strongly enriched, up to a factor of ten with respect to the sun in LS IV + 10° 9. The nickel-to-iron ratio is significantly super-solar. Using spectral energy distributions and Gaia parallaxes the masses of the stars were determined. They are found to scatter around the canonical mass for the core helium flash, although the uncertainties are large. Conclusions. The abundance pattern observed for CD-31°4800 is consistent with predictions of models for slow (cold) mergers of pairs of equal mass helium WDs except for the low oxygen abundance observed. Models for composite mergers were considered for the C-rich stars, but predict abundance pattern dissimilar to those determined. [CW83] 0904-02, though, may be a candidate for a composite He-WD merger, as it rotates and appears to be more massive than the other program stars. New evolutionary models for the hot flasher scenario predict abundance patterns similar to those determined for the C-rich stars. Hence, C-rich He-sdO may well result from late He flashes with deep-mixing episodes.Facultad de Ciencias Astronómicas y GeofísicasInstituto de Astrofísica de La Plat

Clinical presentation of simple and combined or syndromic arteriovenous malformations.

OBJECTIVES Arteriovenous malformations of the lower extremities (AVMLE) can present as simple or complex combined or syndromic forms (e.g. Parkes Weber Syndrome). We aimed to characterize the differences in clinical presentation and natural history of these potentially life and limb threatening congenital vascular malformations. METHODS We conducted a retrospective analysis of a consecutive series of patients with AVMLE, who presented to a tertiary referral center in Switzerland between 2008 and 2018. Clinical baseline characteristics, D-dimer level and course were summarized and differences between simple, non-syndromic and combined or syndromic AVMLE determined. Odds ratios (OR) and 95% confidence intervals (CI) were estimated using logistic regression models. RESULTS Overall, 506 patients were prospectively enrolled in the Bernese Congenital Vascular Malformation Registry, 31 (6%) with AVMLE. There were 16 women and 15 men with a mean age of 18 years at first diagnosis (1 month - 72 years). Simple AVMLE was present in 22 (71%), combined or syndromic AVMLE with limb overgrowth in 9 patients (29%), respectively. Common symptoms and signs were pain 25 (81%), swelling 21 (68%) and soft tissue hypertrophy 13 (42%). Among combined or syndromic patients, 3 patients died from wound infection with sepsis or disseminated intravascular coagulation with bleeding complications (intracranial hemorrhage and bleeding from extensive leg ulcers). Combined or syndromic patients presented more often with bleeding (67% vs. 5%; p<0.001), malformation related infection (44% vs. 5%; p=0,017) and leg length difference (56% vs. 14%; p=0.049). D-dimer levels were elevated (mean 17256 μg/L, range 1557 μg/L to 80000 μg/L) and angiographic appearance showed complex, mixed type of AVMs, including interstitial type IV, in all patients with combined or syndromic AVMLE. CONCLUSION Patients with congenital simple AVMLE most often present with benign clinical features and rarely complications related to hemodynamic changes. Patients with combined or syndromic AVMLE often face serious outcomesdominated by complications other than direct high flow related heart failure