444 research outputs found
FORMALIZATION OF THE PROBLEM OF THE SDN NETWORK PARTITIONING INTO ROUTING ZONES
On of the key goals that should be solved to efficiently organize network routing is splitting the network to, in some sense, optimal set of routing zones. The work considers generalized mathematical formalization of the graph partition problem. Graph defines SDN network topology. According to this topology possible objective functions and constraints were formulated. Objective functions take into account cut parameters, subgraphs and\or cuts boundary vertices characteristics. Constraints take into account weights and probabilities .Key words: software-defined networking, routing zones, graph partition, graph cut, total cut weightкандидат технічних наук, Коган А. В., доктор технічних наук, професор, Кулаков Ю. О., кандидат технічних наук, Сперкач М. О., кандидат технічних наук, доцент, Жданова О. Г. Формалізація задачі розбиття мережі SDN на зони маршрутизації / Національний технічний університет України “Київський політехнічний інститут імені Ігоря Сікорського”, Україна, Київ Однією з ключових задач, що повинні бути розв’язані для організації ефективної маршрутизації в мережах, є розбиття всієї мережі на оптимальну в деякому сенсі кількість зон маршрутизації. В роботі розглядається узагальнена математична формалізація задачі розбиття графу, який описує фізичну топологію мережі SDN. Відповідно цієї топології були сформульовані можливі цільові функції та визначені обмеження задач розбиття графу. Цільові функції враховують параметри розрізів, підграфів та/або характеристики граничних вершин розбиття. Обмеження враховують ваги та ймовірності виключення/виходу з ладу вершин і ребер.Ключові слова: програмно-конфігурована мережа, зони маршрутизації, граф, розбиття графу, розріз графу, гранична вершина, сумарна вага розрізу
Метод оптимизации ярусно-параллельной формы представления задачи для реконфигурируемых вычислительных систем
В роботі запропонований метод оптимізації структури графа задачі, поданого в ярусно-паралельній формі, що враховує вимоги мінімізації часу виконання задачі та обмеження апаратних ресурсів, та дозволяє підвищити продуктивність реконфігурованих обчислювальних систем.The method of optimizing the structure of the task graph represented by a macro dataflow graph, is proposed. The method takes into account the requirement to minimize execution time and the limitations of hardware resources. The method improves the performance of reconfigurable computing systems.В статье предложен метод оптимизации структуры графа задачи, представленного в ярусно-параллельной форме, который учитывает требования минимизации времени выполнения задачи, ограничения аппаратных ресурсов и позволяет повысить производительность реконфигурируемых вычислительных систем
Centrality dependence of identified particle elliptic flow in relativistic heavy ion collisions at sqrt(s)= 7.7--62.4 GeV
Elliptic flow (v_2) values for identified particles at midrapidity in Au + Au
collisions measured by the STAR experiment in the Beam Energy Scan at the
Relativistic Heavy Ion Collider at sqrt{s_{NN}}= 7.7--62.4 GeV are presented
for three centrality classes. The centrality dependence and the data at
sqrt{s_{NN}}= 14.5 GeV are new. Except at the lowest beam energies we observe a
similar relative v_2 baryon-meson splitting for all centrality classes which is
in agreement within 15% with the number-of-constituent quark scaling. The
larger v_2 for most particles relative to antiparticles, already observed for
minimum bias collisions, shows a clear centrality dependence, with the largest
difference for the most central collisions. Also, the results are compared with
A Multiphase Transport Model and fit with a Blast Wave model.Comment: 14 pages, 12 figures, Phys. Rev. C, to be published. Data tables
available at
https://drupal.star.bnl.gov/STAR/publications/centrality-dependence-identified-particle-elliptic-flow-relativistic-heavy-ion-collisi
Observation of charge asymmetry dependence of pion elliptic flow and the possible chiral magnetic wave in heavy-ion collisions
We present measurements of and elliptic flow, , at
midrapidity in Au+Au collisions at 200, 62.4, 39, 27,
19.6, 11.5 and 7.7 GeV, as a function of event-by-event charge asymmetry,
, based on data from the STAR experiment at RHIC. We find that
() elliptic flow linearly increases (decreases) with charge asymmetry
for most centrality bins at and higher.
At , the slope of the difference of
between and as a function of exhibits a
centrality dependence, which is qualitatively similar to calculations that
incorporate a chiral magnetic wave effect. Similar centrality dependence is
also observed at lower energies.Comment: 6 pages, 4 figure
Azimuthal anisotropy in U+U and Au+Au collisions at RHIC
Collisions between prolate uranium nuclei are used to study how particle
production and azimuthal anisotropies depend on initial geometry in heavy-ion
collisions. We report the two- and four-particle cumulants, and
, for charged hadrons from U+U collisions at =
193 GeV and Au+Au collisions at = 200 GeV. Nearly fully
overlapping collisions are selected based on the amount of energy deposited by
spectators in the STAR Zero Degree Calorimeters (ZDCs). Within this sample, the
observed dependence of on multiplicity demonstrates that ZDC
information combined with multiplicity can preferentially select different
overlap configurations in U+U collisions. An initial-state model with gluon
saturation describes the slope of as a function of multiplicity in
central collisions better than one based on Glauber with a two-component
multiplicity model.Comment: Final paper version accepted for publication in Phys. Rev. Lett. New
version includes comparisons to a constituent quark glauber mode
Centrality and transverse momentum dependence of elliptic flow of multi-strange hadrons and meson in Au+Au collisions at = 200 GeV
We present high precision measurements of elliptic flow near midrapidity
() for multi-strange hadrons and meson as a function of
centrality and transverse momentum in Au+Au collisions at center of mass energy
200 GeV. We observe that the transverse momentum dependence of
and is similar to that of and , respectively,
which may indicate that the heavier strange quark flows as strongly as the
lighter up and down quarks. This observation constitutes a clear piece of
evidence for the development of partonic collectivity in heavy-ion collisions
at the top RHIC energy. Number of constituent quark scaling is found to hold
within statistical uncertainty for both 0-30 and 30-80 collision
centrality. There is an indication of the breakdown of previously observed mass
ordering between and proton at low transverse momentum in the
0-30 centrality range, possibly indicating late hadronic interactions
affecting the proton .Comment: 7 pages and 4 figures, Accepted for publication in Physical Review
Letter
Isolation of Flow and Nonflow Correlations by Two- and Four-Particle Cumulant Measurements of Azimuthal Harmonics in 200 GeV Au+Au Collisions
A data-driven method was applied to measurements of Au+Au collisions at
200 GeV made with the STAR detector at RHIC to isolate
pseudorapidity distance -dependent and -independent
correlations by using two- and four-particle azimuthal cumulant measurements.
We identified a component of the correlation that is -independent,
which is likely dominated by anisotropic flow and flow fluctuations. It was
also found to be independent of within the measured range of
pseudorapidity . The relative flow fluctuation was found to be for particles of transverse momentum
less than GeV/. The -dependent part may be attributed to
nonflow correlations, and is found to be relative to the
flow of the measured second harmonic cumulant at
Inclusive charged hadron elliptic flow in Au + Au collisions at = 7.7 - 39 GeV
A systematic study is presented for centrality, transverse momentum ()
and pseudorapidity () dependence of the inclusive charged hadron elliptic
flow () at midrapidity() in Au+Au collisions at
= 7.7, 11.5, 19.6, 27 and 39 GeV. The results obtained with
different methods, including correlations with the event plane reconstructed in
a region separated by a large pseudorapidity gap and 4-particle cumulants
(), are presented in order to investigate non-flow correlations and
fluctuations. We observe that the difference between and
is smaller at the lower collision energies. Values of , scaled by
the initial coordinate space eccentricity, , as a function
of are larger in more central collisions, suggesting stronger collective
flow develops in more central collisions, similar to the results at higher
collision energies. These results are compared to measurements at higher
energies at the Relativistic Heavy Ion Collider ( = 62.4 and 200
GeV) and at the Large Hadron Collider (Pb + Pb collisions at =
2.76 TeV). The values for fixed rise with increasing collision
energy within the range studied (). A comparison to
viscous hydrodynamic simulations is made to potentially help understand the
energy dependence of . We also compare the results to UrQMD
and AMPT transport model calculations, and physics implications on the
dominance of partonic versus hadronic phases in the system created at Beam
Energy Scan (BES) energies are discussed.Comment: 20 pages, 12 figures. Version accepted by PR
Energy dependence of acceptance-corrected dielectron excess mass spectrum at mid-rapidity in Au+Au collisions at and 200 GeV
The acceptance-corrected dielectron excess mass spectra, where the known
hadronic sources have been subtracted from the inclusive dielectron mass
spectra, are reported for the first time at mid-rapidity in
minimum-bias Au+Au collisions at = 19.6 and 200 GeV. The excess
mass spectra are consistently described by a model calculation with a broadened
spectral function for GeV/. The integrated
dielectron excess yield at = 19.6 GeV for
GeV/, normalized to the charged particle multiplicity at mid-rapidity, has
a value similar to that in In+In collisions at = 17.3 GeV. For
= 200 GeV, the normalized excess yield in central collisions is
higher than that at = 17.3 GeV and increases from peripheral to
central collisions. These measurements indicate that the lifetime of the hot,
dense medium created in central Au+Au collisions at = 200 GeV
is longer than those in peripheral collisions and at lower energies.Comment: 9 pages, 6 figure
Charged-to-neutral correlation at forward rapidity in Au+Au collisions at =200 GeV
Event-by-event fluctuations of the ratio of inclusive charged to photon
multiplicities at forward rapidity in Au+Au collision at =200
GeV have been studied. Dominant contribution to such fluctuations is expected
to come from correlated production of charged and neutral pions. We search for
evidences of dynamical fluctuations of different physical origins. Observables
constructed out of moments of multiplicities are used as measures of
fluctuations. Mixed events and model calculations are used as baselines.
Results are compared to the dynamical net-charge fluctuations measured in the
same acceptance. A non-zero statistically significant signal of dynamical
fluctuations is observed in excess to the model prediction when charged
particles and photons are measured in the same acceptance. We find that, unlike
dynamical net-charge fluctuation, charge-neutral fluctuation is not dominated
by correlation due to particle decay. Results are compared to the expectations
based on the generic production mechanism of pions due to isospin symmetry, for
which no significant (<1%) deviation is observed.Comment: 14 pages, 6 figure
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