11,428 research outputs found
An Approach for Realistically Simulating the Performance of Scientific Applications on High Performance Computing Systems
Scientific applications often contain large, computationally-intensive, and
irregular parallel loops or tasks that exhibit stochastic characteristics.
Applications may suffer from load imbalance during their execution on
high-performance computing (HPC) systems due to such characteristics. Dynamic
loop self-scheduling (DLS) techniques are instrumental in improving the
performance of scientific applications on HPC systems via load balancing.
Selecting a DLS technique that results in the best performance for different
problems and system sizes requires a large number of exploratory experiments. A
theoretical model that can be used to predict the scheduling technique that
yields the best performance for a given problem and system has not yet been
identified. Therefore, simulation is the most appropriate approach for
conducting such exploratory experiments with reasonable costs. This work
devises an approach to realistically simulate computationally-intensive
scientific applications that employ DLS and execute on HPC systems. Several
approaches to represent the application tasks (or loop iterations) are compared
to establish their influence on the simulative application performance. A novel
simulation strategy is introduced, which transforms a native application code
into a simulative code. The native and simulative performance of two
computationally-intensive scientific applications are compared to evaluate the
realism of the proposed simulation approach. The comparison of the performance
characteristics extracted from the native and simulative performance shows that
the proposed simulation approach fully captured most of the performance
characteristics of interest. This work shows and establishes the importance of
simulations that realistically predict the performance of DLS techniques for
different applications and system configurations
Simulating chemistry efficiently on fault-tolerant quantum computers
Quantum computers can in principle simulate quantum physics exponentially
faster than their classical counterparts, but some technical hurdles remain.
Here we consider methods to make proposed chemical simulation algorithms
computationally fast on fault-tolerant quantum computers in the circuit model.
Fault tolerance constrains the choice of available gates, so that arbitrary
gates required for a simulation algorithm must be constructed from sequences of
fundamental operations. We examine techniques for constructing arbitrary gates
which perform substantially faster than circuits based on the conventional
Solovay-Kitaev algorithm [C.M. Dawson and M.A. Nielsen, \emph{Quantum Inf.
Comput.}, \textbf{6}:81, 2006]. For a given approximation error ,
arbitrary single-qubit gates can be produced fault-tolerantly and using a
limited set of gates in time which is or ; with sufficient parallel preparation of ancillas, constant average
depth is possible using a method we call programmable ancilla rotations.
Moreover, we construct and analyze efficient implementations of first- and
second-quantized simulation algorithms using the fault-tolerant arbitrary gates
and other techniques, such as implementing various subroutines in constant
time. A specific example we analyze is the ground-state energy calculation for
Lithium hydride.Comment: 33 pages, 18 figure
Autonomous tawaf crowd simulation
Crowd simulation is an exciting research area that has a wide range of applications in multiple fields such as: serious games, crowd management, facilities design, entertainment, research and development. One of the most famous approaches to simulate a large density crowd is by applying the social force model. This model can be successfully used to simulate agents’ movement in real-world scenarios realistically. Nevertheless, this is very simple and not suitable to simulate a complex pedestrian flow movement. Hence, this research proposes a new novel model for simulating the pilgrims’ movements circumambulating the Kaabah (Tawaf). These rituals are complex yet unique, due to its capacity, density, and various demographics backgrounds of the agents (pilgrims). It is also consist a certain set of rules and regulations that must be followed by the agents. Due to these rules, the Tawaf can introduce irregularities in the motion flow around the Kaabah. In order to make the simulations as close as possible to real world scenarios, each agent will be assigned with different attributes such as; age, gender and intention outlook. The three parameter mentioned above, are the main problem that need to be solved in this research in order to simulate a better crowd simulation than previous studies. The findings of this research will contribute greatly for Hajj management in term of controlling and optimizing the flow of pilgrims during Tawaf especially in the Hajj season. It is also have high contribution in Hajj training especially in developing a virtual Hajj training system. The virtual Hajj system can be used to teach and prepare the pilgrims before going to Mecca and perform the actual Hajj
Spectral/hp element methods: recent developments, applications, and perspectives
The spectral/hp element method combines the geometric flexibility of the
classical h-type finite element technique with the desirable numerical
properties of spectral methods, employing high-degree piecewise polynomial
basis functions on coarse finite element-type meshes. The spatial approximation
is based upon orthogonal polynomials, such as Legendre or Chebychev
polynomials, modified to accommodate C0-continuous expansions. Computationally
and theoretically, by increasing the polynomial order p, high-precision
solutions and fast convergence can be obtained and, in particular, under
certain regularity assumptions an exponential reduction in approximation error
between numerical and exact solutions can be achieved. This method has now been
applied in many simulation studies of both fundamental and practical
engineering flows. This paper briefly describes the formulation of the
spectral/hp element method and provides an overview of its application to
computational fluid dynamics. In particular, it focuses on the use the
spectral/hp element method in transitional flows and ocean engineering.
Finally, some of the major challenges to be overcome in order to use the
spectral/hp element method in more complex science and engineering applications
are discussed
What is a quantum simulator?
Quantum simulators are devices that actively use quantum effects to answer
questions about model systems and, through them, real systems. Here we expand
on this definition by answering several fundamental questions about the nature
and use of quantum simulators. Our answers address two important areas. First,
the difference between an operation termed simulation and another termed
computation. This distinction is related to the purpose of an operation, as
well as our confidence in and expectation of its accuracy. Second, the
threshold between quantum and classical simulations. Throughout, we provide a
perspective on the achievements and directions of the field of quantum
simulation.Comment: 13 pages, 2 figure
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