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ZIVIS is an initiative which aims to establish in Zaragoza (Spain) the first “city-wide supercomputer”. The objective is to integrate as much computers as possible to form a virtual computing platform in the metropolitan area of Zaragoza (650.000 inhabitants). This is achieved through volunteer computing, namely using an adapted version of the open source software BOINC.
The project is run by the Zaragoza city council [2] and the Institute for Biocomputation and Physics of Complex Systems [3] of the University of Zaragoza, which will provide the scientific applications to be run on the platform.ISDEP (“Integrator of Stochastic Differential Equations in Plasmas”) is a fusion plasma application programmed and highly optimized in C language which calculates the trajectories of the particles inside a fusion device. This environment is read from several input files which includes the geometry of the vacuum chamber of the fusion device, the magnetic field created by the coils, and the electrostatic and particles (electrons and ions) density profiles. As a result, the same calculus core can be used for a stellarator fusion device or for a tokamak one. The magnetic field is read from a grid (see Guasp et al.[5]) and interpolated in simulation time. The application calculates the next position of each particle along its trajectory as a function of the previous one, taking into consideration the environment and other initial parameters of the particles. These parameters include the possibility of a collision between particles during simulation and the electrical and magnetic fields inside the device. Those effects can be independently "switched off or on" by the user in order to assess its influence in particle evolution.
Actually, the calculation of the positions of the different particles of each trajectory during the simulation implies the solution of a set of Stochastic Differential Equations which governs the evolution of the plasma. The numerical algorithm used for solving them (by Kloeden and Pearson [6]) is of the Runge-Kutta type, upgraded so that it can deal with a gaussian noise (the one caused by the collisions of the particles with ions and electrons inside the device). At the end, the core calculates a great number of particles trajectories (typically about one million) and obtains averages of the relevant magnitudes, such as densities, temperatures and fluxes of particles.Gives a rough idea.The generation of workunits for ISDEP will be differentiated in two phases. In a first round (first four weeks of the production period) clients will calculate a determinate number of trajectories and will take measurements over them, essentially sampling positions using a given interval of time. They will also save a complete trajectory for a posterior visualization during the public demostration event. During the second phase (fifth week), only sampled data will be calculated.
Originally Posted by alpha
