1 High performance Computing Applied to a Saltwater Intrusion Numerical Model E. Canot IRISA/CNRS J. Erhel IRISA/INRIA Rennes C. de Dieuleveult IRISA/INRIA Rennes

2 Outline Context Model and Test Cases Coupled Model Test Cases : Henry and Elder Parallel performances Presentation Results Conclusion

3 Context Effect of pumping in coastal aquifers Necessity to predict the evolution of the water supply. Context

4 Presentation of the software Based on TVDV-2D software developped at IMFS in Strasbourg Simulation of density driven coupled flow and transport in a porous media Originally sequential Coupled Model

5 Model FLOW TRANSPORTconvection dispersion Coupled Model

6 Strong Coupling Concentration Time n FLOWTRANSPORT Velocity Density Time n+1 Coupled Model

7 Henry Stable test case Test Cases

8 Elder Unstable test case Test Cases

9 First parallel version (v1) Parallel performances Parallel linear solvers

10 Parallel sparse solver Use of MUMPS (« MUltifrontal Massively Parallel Solver »), a free package for solving linear systems of equations Ax=b Adapted for sparse unsymmetric, and symmetric definite positive matrices. Parallel performances

11 Global parallelisation (v2) Partitioning mesh thanks to METIS, a free package for partitioning graphs, meshes and for producing fill reducing orderings for sparse matrices. Partitioning example with 5 parts Better data distribution. Parallel performances

12 Time step number 1 processor2 processors Iteration number Time step (in day) Iteration number Time step (in day) 1101/4101/4 2 to 7121/4121/4 826 (no convergence) 1/4111/4 1/81/4 Results Due to the convergence criterion Elder (mesh 256x160) Sensitivity to convergence criterion

13 Sensitivity to convergence criterion Results Elder (mesh 256x160), time step number 8

14 Wall clock (in seconds) Number of processors Results Results for the first version (v1) Henry (mesh 510x254)

15 Number of processors Results Results for the second version (v2) Wall clock (in seconds) Henry (mesh 510x254)

16 Conclusion - Perspectives 3D geometry Adaptative mesh Improved coupling Conclusion