A conservative strategy to protect P2P file sharing systems from pollution attacks

Despite being currently one of the main Internet applications, P2P file sharing has been hampered by content pollution attacks. To tackle this problem, we introduce a novel pollution control strategy that consists in adjusting the rate in which content is disseminated, according to content version reputation. The proposed strategy is modeled and evaluated using simplifying assumptions. Then, inspired by classic distributed designs, we propose a pollution control mechanism that implements such a strategy. The mechanism is evaluated in terms of the delays imposed on non‐polluted version dissemination, the effectiveness of reducing dissemination when the version is polluted, and the negative impact that collusion attacks can impose on the reputation system upon which our mechanism is built. Simulation results looking at scenarios with several hundred peers indicate that the pollution control mechanism can effectively reduce pollution without substantially affecting the dissemination of non‐polluted content. Copyright © 2010 John Wiley & Sons, Ltd.     

A program for accurate solutions of two-electron atoms

We present a comprehensible computer program capable of treating non-relativistic ground and excited states for a two-electron atom having infinite nuclear mass. An iterative approach based on the implicitly restarted Arnoldi method (IRAM) is employed. The Hamiltonian matrix is never explicitly computed. Instead the action of the Hamiltonian operator on discrete pair functions is implemented. The finite difference method is applied and subsequent extrapolations gives the continuous grid result. The program is written in C and is highly optimized. All computations are made in double precision. Despite this relatively low degree of floating point precision (48 digits are not uncommon), the accuracy in the results can reach about 10 significant figures. Both serial and parallel versions are provided. The parallel program is particularly suitable for shared memory machines such as the Sun Starcat series. The serial version is simple to compile and should run on any platform.

Program summary

Title of program: corr2elCatalogue identifier: ADUXProgram summary URL:http://cpc.cs.qub.ac.uk/summaries/ADUXProgram obtainable from:CPC Program Library, Queen's University of Belfast, N. IrelandDistribution format: tar.gzComputer for which the program is designed and others on which it has been tested:Computers: Sun Fire 15K StarCat, Sun Ultra SPARC III, PCOperating systems or monitors under which the program has been tested: Sun Solaris 9, LinuxProgramming language used: ANSI CMemory required to execute with typical data: 3 Mwords or moreNo. bits in a word: 32No. processors used: arbitraryHas the code been vectorized or parallelized: parallelizedNumber of lines in distributed program, including test data, etc.:5885Number of bytes in distributed program, including test data, etc.: 26 199Nature of physical problem: The Schrödinger equation for two-electron atoms is solved using finite differences.Method of solution: An iterative eigenvalue-solver that requires only the action of the Hamiltonian on a trial function is applied. The two-electron wave function is expanded in a sum of partial waves. The finite difference method is then applied to approximate the derivatives of the pair functions. The total action of the Hamiltonian on the partial waves, including correlation effects, is computed using highly optimized routines.Restriction on the complexity of the problem: The Hamiltonian employed here does not take relativistic or finite nuclear mass effects into account. The amount of computing time may become unreasonable for excited states far above the ground state. The use of double precision puts a limit on the accuracy obtainable.Typical running time: This ranges from half a minute (to obtain 10 significant figures for the s-limit of the Helium ground state) to perhaps a day for advanced examples depending on the level of parallelization.Unusual features of the program: The implicitly restarted Arnoldi method used to obtain the eigenvalues is implemented by using the ARPACK/PARPACK program library [http://www.netlib.org/arpack]. This package also depends on the standard numerical libraries BLAS and LAPACK [http://www.netlib.org/lapack]. Good performance is obtained by using Sun's optimized performance libraries [http://www.sun.com]. By using a 64-bit environment (Ultra SPARC III and Solaris 9), memory limitations are non-problematic. Shared memory is used in the parallel version. Fast communication between the nodes is made over shared memory using Sun's implementation of MPI.     

P2P as a CDN: A new service model for file sharing

Traditional content distribution networks (CDNs), such as Akamai, replicate content at thousands of servers worldwide in an attempt to bring it closer to end users. Recent years have, however, brought a surge of peer-to-peer (p2p) systems that have demonstrated the ability both to help traditional CDN operations and to effectively disseminate content as independent applications. Unfortunately, this p2p surge has created significant problems to network operators by generating large volumes of inter-AS traffic. In this paper, we demonstrate that stepping back and applying traditional CDN design principles to p2p systems can help solve these emerging problems. In particular, focusing on the BitTorrent swarming protocol, we show that our new service model can, in the common case, reduce inter-AS traffic by 45–75%. Moreover, in scenarios when ISPs are shaping inter-AS traffic, it speeds up download times by 60% for the most popular torrents.Our approach bases on disproving the common wisdom that the current peer altruism in p2p systems (BitTorrent in particular) is insufficient. We thus abandon the common approach of deploying novel incentives for cooperation, and focus on designing methods to effectively utilize existing system resources. We show that controlled regional-based content replication, common for the traditional CDN design, can effectively achieve this goal. We implement our system and demonstrate that it effectively scales. Moreover, it is incrementally deployable and brings significant benefits in partial deployment scenarios. ISPs and network regions in which the system gets deployed can resolve their inter-AS traffic problems instantly and autonomously, i.e., without any inter-ISP collaboration and without requiring that the system gets deployed in the entire Internet.     

X-File: a program for maintaining a radiographic teaching file

Software designed for entry, retrieval, and maintenance of radiographic case-file data on a microcomputer offers considerable help in maintaining such records in a radiology department. The case files are based on the Index for Roentgen Diagnoses, published by the AmericanCollege of Radiology. The terms and code numbers of the index are included in the software, so that the user need only enter the diagnostic term desired; the code numbers and exact terminology are assigned automatically. The software is written for an IBM-compatible microcomputer. Residents and staff radiologists have been using the program for the past two years to store and find both confirmed cases and other interesting cases. The system's capacity exceeds 70,000 entries on a 20-megabyte had disk. The program has five features not found in previous similar programs and not attainable with manual methods.     

A program to compute exact hydrogenic radial integrals and Einstein coefficients

An exact expression for the dipole radial integral of hydrogen has been given by Gordon [Ann. Phys. 2 (1929) 1031]. It contains two hypergeometric functions F(a,b;c;x), which are difficult to calculate directly, when the (negative) integers a, b are large, as in the case of high Rydberg states of hydrogenic ions. We have derived a simple method [D. Hoang-Binh, Astron. Astrophys. 238 (1990) 449], using a recurrence relation to calculate exactly F, starting from two initial values, which are very easy to compute. We present here a numerical code using this method. The code computes exact hydrogenic radial integrals, oscillator strengths, Einstein coefficients, and lifetimes, for principal quantum numbers up to 1000.

Program summary

Program title: ba5.2Catalogue identifier: ADUU_v2_0Program summary URL:http://cpc.cs.qub.ac.uk/summaries/ADUU_v2_0.htmlProgram obtainable from: CPC Program Library, Queen's University, Belfast, N. IrelandLicensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.htmlNo. of lines in distributed program, including test data, etc.: 1400No. of bytes in distributed program, including test data, etc.: 11 737Distribution format: tar.gzProgramming language: Fortran 77Computer: PC, iMacOperating system: Linux/Unix, MacOS 9.0RAM: Less than 1 MBClassification: 2, 2.2Catalogue identifier of previous version: ADUU_v1_0Journal reference of previous version: Comput. Phys. Comm. 166 (2005) 191Does the new version supersede the previous version?: YesNature of problem: Exact calculation of atomic data.Solution method: Use of a recurrence relation to compute hypergeometric functions.Reasons for new version: This new version computes additional important related data, namely, the total Einstein coefficients, and radiative lifetimes.Summary of revisions: Values of the total Einstein transition probability from an upper level n to a lower level n^′ are computed, as well as the radiative lifetime of a level n.Running time: About 2 seconds     

一种获取关联程序启动路径的方法与实现

本文介绍了安装可执行程序修改注册表建立文件关联链表的过程,提出了一种基于文件类型获取关联应用程序启动路径的方法,并给出了用VB 6.0语言实现的程序代码.     

一种获取关联程序启动路径的方法与实现

本文介绍了安装可执行程序修改注册表建立文件关联链表的过程,提出了一种基于文件类型获取关联应用程序启动路径的方法,并给出了用VB6.0语言实现的程序代码。     

golem95: A numerical program to calculate one-loop tensor integrals with up to six external legs

We present a program for the numerical evaluation of form factors entering the calculation of one-loop amplitudes with up to six external legs. The program is written in Fortran95 and performs the reduction to a certain set of basis integrals numerically, using a formalism where inverse Gram determinants can be avoided. It can be used to calculate one-loop amplitudes with massless internal particles in a fast and numerically stable way.

Program summary

Program title: golem95_v1.0Catalogue identifier: AEEO_v1_0Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEEO_v1_0.htmlProgram obtainable from: CPC Program Library, Queen's University, Belfast, N. IrelandLicensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.htmlNo. of lines in distributed program, including test data, etc.: 50 105No. of bytes in distributed program, including test data, etc.: 241 657Distribution format: tar.gzProgramming language: Fortran95Computer: Any computer with a Fortran95 compilerOperating system: Linux, UnixRAM: RAM used per form factor is insignificant, even for a rank six six-point form factorClassification: 4.4, 11.1External routines: Perl programming language (http://www.perl.com/)Nature of problem: Evaluation of one-loop multi-leg tensor integrals occurring in the calculation of next-to-leading order corrections to scattering amplitudes in elementary particle physics.Solution method: Tensor integrals are represented in terms of form factors and a set of basic building blocks (“basis integrals”). The reduction to the basis integrals is performed numerically, thus avoiding the generation of large algebraic expressions.Restrictions: The current version contains basis integrals for massless internal particles only. Basis integrals for massive internal particles will be included in a future version.Running time: Depends on the nature of the problem. A rank 6 six-point form factor at a randomly chosen kinematic point takes 0.13 seconds on an Intel Core 2 Q9450 2.66 GHz processor, without any optimisation. With compiler optimisation flag -O3 the same point takes 0.09 seconds. Timings for lower point form factors are: All form factors for five-point functions from rank 0 to rank 4: 0.04 s. All form factors for rank 5 five-point functions: 0.05 s. All form factors for four-point functions from rank 0 to rank 4: 0.01 s.     

FRODO: a MuPAD program to calculate matrix elements between contracted wavefunctions

A symbolic program performing the Formal Reduction of Density Operators (FRODO) has been developed in the MuPAD computer algebra system with the purpose of evaluating the matrix elements of the electronic Hamiltonian between internally contracted functions in a complete active space (CAS) scheme. The program is illustrated making use of two meaningful examples.

Program summary

Title of program:FRODOCatalogue identifier:ADVYProgram summary URL:http://cpc.cs.qub.ac.uk/summaries/ADVYProgram obtainable from: CPC Program Library, Queen's University of Belfast, N. IrelandComputer:Any computer on which the MuPAD computer algebra system can be installedOperating systems under which the program has been tested:LinuxProgramming language used:MuPAD vs. 2.5.3 for LinuxNo. of lines in distributed program, including test data, etc.:3939No. of bytes in distributed program, including test data, etc.:19 661Distribution format:tar.gzNature of physical problem: In order to improve on the CAS-SCF wavefunction one can resort to multireference perturbation theory or configuration interaction based on internally contracted functions (ICF) which are obtained by application of the excitation operators to the reference CAS-SCF wavefunction. The formulation of such matrix elements is quite cumbersome and a computer algebra system like MuPAD appears ideally suited to perform such a task.Method of solution: The method adopted consists in successively eliminating all occurrences of inactive orbital indices (core and virtual) from the products of excitation operators which appear in the definition of the ICF's and in the electronic Hamiltonian expressed in the second quantization formalism.Restrictions due to the complexity of the problem: The program is limited to no more than doubly excited ICF's.     

PSON: A scalable P2P file sharing system with efficient complex query support

A desired P2P file sharing system is expected to achieve the following design goals: scalability, routing efficiency and complex query support. In this paper, we propose a powerful P2P file sharing system, PSON, which can satisfy all the three desired properties. PSON is essentially a semantic overlay network of logical nodes. Each logical node represents a cluster of peers that are close to each other. A powerful peer is selected in each cluster to support query routing on the overlay network while the less powerful peers are responsible for the maintenance of shared contents. To facilitate query routing, super peers are organized in form of a balanced binary search tree. By exploiting the concept of semantics, PSON can support complex queries in a scalable and efficient way. In this paper, we present the basic system design such as the semantic overlay construction, query routing and system dynamics. A load balancing scheme is proposed to further enhance the system performance. By simulation experiments, we show that PSON is scalable, efficient and is able to support complex queries.     

A pascal program suitable to solve large sparse linear systems on personal computers

Large and very sparse linear systems are common in many real problems, such as those involving electrical networks, structural analyses, power distribution systems, nuclear reactor and operational research. In this paper a Pascal program suitable to solve such a kind of problem is given. The program is tailored to be used on personal computers. The code is based on the classical Gauss-Seidel iterative method.     

TSIL: a program for the calculation of two-loop self-energy integrals

TSIL is a library of utilities for the numerical calculation of dimensionally regularized two-loop self-energy integrals. A convenient basis for these functions is given by the integrals obtained at the end of O.V. Tarasov's recurrence relation algorithm. The program computes the values of all of these basis functions, for arbitrary input masses and external momentum. When analytical expressions in terms of polylogarithms are available, they are used. Otherwise, the evaluation proceeds by a Runge-Kutta integration of the coupled first-order differential equations for the basis integrals, using the external momentum invariant as the independent variable. The starting point of the integration is provided by known analytic expressions at (or near) zero external momentum. The code is written in C, and may be linked from C/C++ or Fortran. A Fortran interface is provided. We describe the structure and usage of the program, and provide a simple example application. We also compute two new cases analytically, and compare all of our notations and conventions for the two-loop self-energy integrals to those used by several other groups.

Program summary

Title of program:TSILVersion number: 1.0Catalogue identifier: ADWSProgram summary URL:http://cpc.cs.qub.ac.uk/summaries/ADWSProgram obtainable from: CPC Program Library, Queen's University of Belfast, N. IrelandProgramming language: CPlatform: Any platform supporting the GNU Compiler Collection (gcc), the Intel C compiler (icc), or a similar C compiler with support for complex mathematicsNo. of lines in distributed program, including test data, etc.: 42 730No. of bytes in distributed program, including test data, etc.: 297 101Distribution format: tar.gzNature of physical problem: Numerical evaluation of dimensionally regulated Feynman integrals needed in two-loop self-energy calculations in relativistic quantum field theory in four dimensions.Method of solution: Analytical evaluation in terms of polylogarithms when possible, otherwise through Runge-Kutta solution of differential equations.Limitations: Loss of accuracy in some unnatural threshold cases that do not have vanishing masses.Typical running time: Less than a second.     

ModDRE: A program to model deepwater-reservoir elements using geomorphic and stratigraphic constraints

In deepwater-reservoir modeling, the proper representation of the spatial distribution of architectural elements is important to account for pore-volume distribution and the connectivity of reservoir sand bodies. This is especially critical for rock and fluid-volume estimates, reservoir-performance predictions, and development-well planning.A new integrated stochastic reservoir-modeling approach (ModDRE—Modeling Deepwater Reservoir Elements) accounts for geomorphic and stratigraphic controls to generate the deepwater-reservoir architecture. Information on stratal-package evolution and sediment provenance can be integrated into the reservoir-modeling process. A slope-area analytical approach is implemented to account for topographical constraints on channel and sheet-form reservoir architectures and their distribution. Inferred sediment–source statistics and architectural-element variability (from seismic, outcrop, and stratigraphic studies) associated with relative changes in sea level can also be used to constrain the deepwater-reservoir-element statistics. Based on these geomorphic and stratigraphic constraints, deepwater-reservoir elements (channels, lobes) are built into the model sequentially (in stratigraphic order).Integration of realistic geological and engineering attributes into deepwater-reservoir models is vital for optimal reservoir management. This approach is unique in that it is more directly constrained to geomorphic and stratigraphic parameters than traditional object- or surface-based techniques for stochastic deepwater-reservoir modeling.     

On the estimation of a large sparse Bayesian system: The Snaer program

The Snaer program calculates the posterior mean and variance of variables on some of which we have data (with precisions), on some we have prior information (with precisions), and on some prior indicator ratios (with precisions) are available. The variables must satisfy a number of exact restrictions. The system is both large and sparse. Two aspects of the statistical and computational development are a practical procedure for solving a linear integer system, and a stable linearization routine for ratios. The numerical method for solving large sparse linear least-squares estimation problems is tested and found to perform well, even when the n×k design matrix is large (nk=O(10⁸)).     

PDSW: A program for the calculation of photon energy distribution resulting from radioactive elements in seawater

Photons, when emitted from radioactive sources in seawater, are subsequent to multiple scattering mechanisms, namely the photoelectric effect, the Compton scattering and the pair production effect. Thus, the monoenergetic emission of photons in seawater will result in equilibrium in a distribution of photons with different energies. PDSW is a MATLAB program which calculates this distribution and can be found useful for the characterization of measured spectra obtained by gamma detectors such as NaI(Tl). PDSW has been developed as an autonomous MATLAB function in order to make possible to integrate it in other applications. All calculations are performed using a typical value for seawater salinity (3.5%).

Program summary

Title of program: PDSWCatalogue identifier: ADWWProgram summary URL:http://cpc.cs.qub.ac.uk/summaries/ADWWProgram obtainable from: CPC Program Library, Queen's University of Belfast, N. IrelandComputer: x86Operating systems: WindowsProgramming language used: MATLABMemory required: 10 MbNumber of bits in a word: 32Number of processors used: 1Vectorized or parallelized?: noNumber of bytes in distributed program, including test data, etc.: 16 378Number of lines in distributed program, including test data, etc.: 3004Distribution format:tar.gzCPC Program Library subprograms used: noneNature of physical problem: Calculation of photon energy distribution in seawater taking into account the photoelectric effect, the Compton scattering and the pair production effect.Method of solution: Analytical calculation of the continuity equation for photon energy distribution in seawater and numerical integration of this equation in equilibrium.Restrictions on the complexity of the program: Very small resolution results in large memory requirements and high execution time.Typical running time: (Maximum energy-minimum resolution) 20 sUnusual features of the program: none