157 research outputs found
TMbarrier: speculative barriers using hardware transactional memory
Barrier is a very common synchronization method used in parallel programming. Barriers are used typically to enforce a partial thread execution order, since there may be dependences between code sections before and after the barrier. This work proposes TMbarrier, a new design of a barrier intended to be used in transactional applications. TMbarrier allows threads to continue executing speculatively after the barrier assuming that there are not dependences with safe threads that have not yet reached the barrier. Our design leverages transactional memory (TM) (specifically, the implementation offered by the IBM POWER8 processor) to hold the speculative updates and to detect possible conflicts between speculative and safe threads. Despite the limitations of the best-effort hardware TM implementation present in current processors, experiments show a reduction in wasted time due to synchronization compared to standard barriers.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech
Strong pinning of vortices by antiferromagnetic domain boundaries in CeCo(InCd)
We have studied the isothermal magnetization of
CeCo(InCd) with = 0.0075 and 0.01 down to 50 mK. Pronounced
field-history dependent phenomena occur in the coexistence regime of the
superconducting and antiferromagnetic phases. At low-fields, a phenomenological
model of magnetic-flux entry well explains implying the dominance of
bulk pinning effect. However, unless crystallographic quenched disorder is
hysteretic, the asymmetric peak effect (ASPE) which appears at higher fields
cannot be explained by the pinning of vortices due to material defects. Also
the temperature dependence of the ASPE deviates from the conventional scenario
for the peak effect. Comparison of our thermodynamic phase diagrams with those
from previous neutron scattering and magnetoresistance experiments indicates
that the pinning of vortices takes place at the field-history dependent
antiferromagnetic domain boundaries.Comment: 13 pages,4 figures, to be published in New Journal of Physic
Desarrollo de un método numérico para la determinación del mapa tensional en la zona de contacto entre dos cuerpos
Se presenta un método numérico para la determinación del mapa tensional en la zona de contacto entre
dos cuerpos, a partir de la distribución de presiones sobre la superficie. Este método permite determinar
el campo de tensiones cerca de la superficie. Se ha aplicado a las superficies lubricadas donde la picadura
es el tipo de fallo más usual en componentes mecánicos como engranajes, cojinetes, etc. Se han usado dos
modelos de lubricación: el numérico de Dowson y Higginson, y el analítico de Greenwood. Los resultados
muestran que hay una influencia importante de la lubricación sobre la localización del origen de la grieta de
la picadura en la superficie y no en la subsuperficie.Peer Reviewe
Magnetization study of the energy scales in YbRhSi under chemical pressure
We present a systematic study of the magnetization in YbRhSi
under slightly negative (6?% Ir substitution) and positive (7% Co substitution)
chemical pressure. We show how the critical field , associated with the
high-field Lifshitz transitions, is shifted to lower (higher) values with Co
(Ir) substitution. The critical field , which identifies the
boundary line of the antiferromagnetic (AFM) phase
increases with positive pressure and it approaches zero with 6% Ir
substitution. On the other side, the crossover field , associated with
the energy scale where a reconstruction of the Fermi surface has
been observed, is not much influenced by the chemical substitution.}{Following
the analysis proposed in
Refs.\,\cite{Paschen2004,Gegenwart2007,Friedemann2009,Tokiwa2009a} we have
fitted the quantity with a crossover function to
indentify . The line follows an almost linear -dependence
at sufficiently high fields outside the AFM phase, but it deviates from
linearity at and in
Yb(RhCo)Si it changes slope clearly inside the
AFM phase. Moreover, the FWHM of the fit function depends linearly on
temperature outside the phase, but remains constant inside, suggesting either
that such an analysis is valid only for or that the
Fermi surface changes continuously at inside the AFM phase.}}Comment: 6 pages, 4 figure
Non-Invasive Breast Cancer Diagnosis through Electrochemical Biosensing at Different Molecular Levels
The rapid and accurate determination of specific circulating biomarkers at different molecular levels with non- or minimally invasive methods constitutes a major challenge to improve the breast cancer outcomes and life quality of patients. In this field, electrochemical biosensors have demonstrated to be promising alternatives against more complex conventional strategies to perform fast, accurate and on-site determination of circulating biomarkers at low concentrations in minimally treated body fluids. In this article, after discussing briefly the relevance and current challenges associated with the determination of breast cancer circulating biomarkers, an updated overview of the electrochemical affinity biosensing strategies emerged in the last 5 years for this purpose is provided highlighting the great potentiality of these methodologies. After critically discussing the most interesting features of the electrochemical strategies reported so far for the single or multiplexed determination of such biomarkers with demonstrated applicability in liquid biopsy analysis, existing challenges still to be addressed and future directions in this field will be pointed out
Field-Pulse-Induced Annealing of 2D Colloidal Polycrystals
Funding: This work has been funded by the Ministry of Science and Innovation (Grants No. PID2019- 105343GB-I00 and PID2019-105195RA-I00) and the project EUR2021-122001. Acknowledgments: We thank Andrés González-Banciella and Alba Camino for initial experimentsTwo-dimensional colloidal crystals are of considerable fundamental and practical importance. However, their quality is often low due to the widespread presence of domain walls and defects. In this work, we explored the annealing process undergone by monolayers of superparamagnetic colloids adsorbed onto fluid interfaces in the presence of magnetic field pulses. These systems present the extraordinary peculiarity that both the extent and the character of interparticle interactions can be adjusted at will by simply varying the strength and orientation of the applied field so that the application of field pulses results in a sudden input of energy. Specifically, we have studied the effect of polycrystal size, pulse duration, slope and frequency on the efficiency of the annealing process and found that (i) this strategy is only effective when the polycrystal consists of less than approximately 10 domains; (ii) that the pulse duration should be of the order of magnitude of the time required for the outer particles to travel one diameter during the heating step; (iii) that the quality of larger polycrystals can be slightly improved by applying tilted pulses. The experimental results were corroborated by Brownian dynamics simulations.Depto. de Estructura de la Materia, Física Térmica y ElectrónicaFac. de Ciencias FísicasTRUEMinisterio de Ciencia e Innovación (MCIN)pu
Mejorando el rendimiento de la memoria transaccional para aplicaciones irregulares
La Memoria Transaccional (TM) ofrece un modelo de ejecución concurrente optimista en arquitecturas multinúcleo, permitiendo a los programadores extraer paralelismo cuando la información de las dependencias de datos no está disponible hasta la ejecución ́del programa. Existe investigación reciente enfocada a explotar paralelismo a nivel de hilo usando TM. Sin embargo estas propuestas son de uso general, válidas para cualquier tipo de aplicación.
Este trabajo presenta ReduxSTM, un TM software especialmente diseñado para mejorar la extracción de paralelismo en aplicaciones irregulares. La gestión de las versiones y la detección de conflictos se han diseñado para aprovechar tanto la ordenación secuencial de las transacciones, necesaria para asegurar la corrección de los resultados, como la privatización de
patrones de reducción, un patrón de acceso a memoria muy frecuente en aplicaciones irregulares. La información adicional que proporcionan estas propiedades en tiempo de ejecución se utiliza para evitar abortos transaccionales innecesarios.
Se ha elegido una función del benchmark 300.twolf de la suite SPEC CPU2000 como ejemplo de programa irregular con reducciones. Este código se ha paralelizado mediante TM utilizando ReduxSTM y una versión ordenada de TinySTM. Los resultados muestran que ReduxSTM es capaz de explotar más paralelismo
Improving Transactional Memory Performance for Irregular Applications
Postprint de autor publicado posteriormente con este DOI:http://dx.doi.org/10.1016/j.procs.2015.05.398Transactional memory (TM) offers optimistic concurrency support in modern multicore archi-
tectures, helping the programmers to extract parallelism in irregular applications when data
dependence information is not available before runtime. In fact, recent research focus on ex-
ploiting thread-level parallelism using TM approaches. However, the proposed techniques are
of general use, valid for any type of application.
This work presents ReduxSTM, a software TM system specially designed to extract maxi-
mum parallelism from irregular applications. Commit management and conflict detection are
tailored to take advantage of both, sequential transaction ordering to assure correct results,
and privatization of reduction patterns, a very frequent memory access pattern in irregular
applications. Both techniques are used to avoid unnecessary transaction aborts.
A function in 300.twolf package from SPEC CPU2000 was taken as a motivating irregular
program. This code was parallelized using ReduxSTM and an ordered version of TinySTM,
a state-of-the-art TM system. Experimental evaluation shows that ReduxTM exploits more
parallelism from the sequential program and obtains better performance than the other system.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech
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