Fusion Simulations, data visualization and future requirements for the interactive grid infraestructure F. Castejón 1, D. López Bruna 1, J.M. Reynolds 2, A. Tarancón 2, R. Vallés 2, J.L. Velasco 2 1. Instituto de Biocomputación y Física de Sistemas Complejos 2. Laboratorio nacional de Fusión-Asociación Euratom/Ciemat Madrid, Spain.

WWW on Fusion What is Fusion? What is Fusion? Increasing the temperature of a gas, we get a plasma stateIncreasing the temperature of a gas, we get a plasma state At this temperature, the union of light atom nuclei is possible through an exothermal process:At this temperature, the union of light atom nuclei is possible through an exothermal process: Mass after fusion process less than before it Mass after fusion process less than before it Exceeding mass -> energy Exceeding mass -> energy Why Fusion? Why Fusion? Long-term safe and enviromentally friendlyLong-term safe and enviromentally friendly Delocalized fuel: water and lithiumDelocalized fuel: water and lithium When Fusion? When Fusion? ITER will produce about 400MW of power excess, and it is the previous step to DEMO, a demostration reactor, the last stage (50 years) ‏ITER will produce about 400MW of power excess, and it is the previous step to DEMO, a demostration reactor, the last stage (50 years) ‏ High Temperatures GAS PLASMA

THEORETICAL MODELS

PLASMA SIMULATION Why? Why? Reach a better understanding of plasma physics is necessary to obtain good modelsReach a better understanding of plasma physics is necessary to obtain good models Not expensive, compared with the experimentNot expensive, compared with the experiment Very FlexibleVery Flexible What? What? Under several non-restrictive assumptions, the plasma is modeled by the equations:Under several non-restrictive assumptions, the plasma is modeled by the equations: Guiding center aproximationGuiding center aproximation Evolution of the distribution function for every specie:Evolution of the distribution function for every specie: Convection terms Convection terms Collision terms Collision terms

Solving GC plasma equation The parameters are: The parameters are: Magnetic field (supose fixed) ‏Magnetic field (supose fixed) ‏ Electric field (for the moment supose fixed) ‏Electric field (for the moment supose fixed) ‏ The only aditional non linearity are the collision terms The only aditional non linearity are the collision terms Even assuming all previous simplifications, it is not possible to obtain a general analytical solution in the 5D space. Even assuming all previous simplifications, it is not possible to obtain a general analytical solution in the 5D space. It is neccesary to obtain numerical solutions. Two possible ways are: It is neccesary to obtain numerical solutions. Two possible ways are: Langevin approachLangevin approach Direct approachDirect approach

Linealizing the collision term: Linealizing the collision term: Equivalent to applying a thermal bathEquivalent to applying a thermal bath Then, equation has a Focker- Planck equivalent:Then, equation has a Focker- Planck equivalent: This is, the evolution of the distribution function is equivalent to solve many independent test particles trajectories collisioning with a fixed background caracterized through noise terms. Relatively easy to gridify (no communication between particles) ‏ Langevin Approach: ISDEP

Solve directly the equation to get the distribution function: Solve directly the equation to get the distribution function: Get a magnetic geometry adapted meshing in 3D spatial dimensions.Get a magnetic geometry adapted meshing in 3D spatial dimensions. Get a truncated spectral expansion of the DF in space and velocity:Get a truncated spectral expansion of the DF in space and velocity: If mesh is shared between computation nodes, the parallelization is not trivial, not as easy to gridify If mesh is shared between computation nodes, the parallelization is not trivial, not as easy to gridify Direct aproach

IMPLEMENTATION IMPLEMENTATION

Adaptation of IVISDEP TO INT.EU.GRID Use case:Opengl+GLUT+MPI+i2glogin+ Gvid+Migrating Desktop Use case:Opengl+GLUT+MPI+i2glogin+ Gvid+Migrating Desktop

IVISDEP running on int2grid. Different instances of IVISDEP running on the grid and visualized using MD. Different instances of IVISDEP running on the grid and visualized using MD.

Direct Approach Not implemented, only proposed. Not implemented, only proposed. Viability: Viability: Computation: O(Nv 2 Np 2 ) Transmision (Nv 1/3 +1) 2 Np

Direct Approach: An example Node A Node B 100 Hex (100x27 modes) ‏ (1 sec/iteration) ‏ 100 modes * 16 data * 8 bytes/data = 12.8 kbytes/surface 100 Hex (100x27 modes) ‏ (1 sec/iteration) ‏ 12.8kbytes *100 Hex=1.2 MB/s Node 2Node 3Node 4Node 5Node 6Node 7Node 1 Total bandwidth/node=2.4MB/s full duplex

Data management and visualization on the grid Analyze and visualize the big amount of data generated (more than 100GB per simulation): Analyze and visualize the big amount of data generated (more than 100GB per simulation): If looking for something it is not easy what to look at.If looking for something it is not easy what to look at. So, ideally, the more you can see the more you can find.So, ideally, the more you can see the more you can find. Data distributed around the SE on the grid. Data distributed around the SE on the grid. Could be possible for the user to: Could be possible for the user to: Interact with the remotelly stored dataInteract with the remotelly stored data Analyze data in real time on the gridAnalyze data in real time on the grid Visualize a complex graphical representation generated on the gridVisualize a complex graphical representation generated on the grid

Proposed model

Conclusions Grid has demostrated to be useful for the Fusion community through developed INT.EU.GRID applications (IVISDEP) ‏ Grid has demostrated to be useful for the Fusion community through developed INT.EU.GRID applications (IVISDEP) ‏ Next applications seem to be more parallel demanding codes. Here we propose one Next applications seem to be more parallel demanding codes. Here we propose one We propose too an interactive data visualization and management application for scientific results analysis We propose too an interactive data visualization and management application for scientific results analysis

Thank you! Questions? Questions?