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Approaches to Distributed Execution of Scientific Workflows in Kepler

Płóciennik M., Żok T., Altintas I., Wang J., Crawl D., Abramson D., Imbeaux F., Guillerminet B., Lopez-Caniego M., Campos Plasencia I., Pych W., Ciecieląg P., Palak B., Owsiak M., Frauel Y.

Fundamenta Informaticae

2013

Vol. 128, nr 3

281--302

The Kepler scientific workflow system enables creation, execution and sharing of workflows across a broad range of scientific and engineering disciplines while also facilitating remote and distributed execution of workflows. In this paper, we present and compare different approaches to distributed execution of workflows using the Kepler environment, including a distributed data-parallel framework using Hadoop and Stratosphere, and Cloud and Grid execution using Serpens, Nimrod/K and Globus actors. We also present real-life applications in computational chemistry, bioinformatics and computational physics to demonstrate the usage of different distributed computing capabilities of Kepler in executable workflows. We further analyze the differences of each approach and provide a guidance for their applications.

Local Group Velocity Versus Gravity: Nonlinear Effects

Ciecieląg P., Chodorowski M., Kudlicki A.

Acta Astronomica

2001

Vol. 51, No. 2

103--115

We use numerical simulations to study the relation between the velocity of the Local Group (LG) and its gravitational acceleration. This relation serves as a test for the kinematic origin of the CMB dipole and as a method for estimating β≡Ω0.6/b. We calculate the misalignment angle between the two vectors and compare it to the observed value for the PSCz survey. The latter value is beyond the upper limit of the 90% confidence interval for the angle; therefore, the nonlinear effects are unlikely to be responsible for the whole observed misalignment. We also study the relation between the amplitudes of the LG velocity and gravity vectors. In an Ω=1 Universe, the smoothed gravity of the LG turns out to be a biased low estimator of the LG (unsmoothed) velocity. In an Ω=0.3 Universe, the estimator is biased high. The discussed biases are, however, only a few per cent, thus the linear theory works to good accuracy. The gravity-based estimator of the LG velocity has also a scatter that limits the precision of the estimate of β in the LG velocity-gravity comparisons. The random error of β due to nonlinear effects amounts to several per cent.