1. Porting the MIT Global Circulation Model on the CellBE Processor
Marco POLLINI (1), Paolo PALAZZARI (1,2), Vittorio ROSATO (1,2)
(1) Ylichron Srl, Roma
(2) ENEA CRESCO Project , Casaccia Research Centre, Roma
February 11 , 2009
Workshop Progetti GRID PON Ricerca, Catania 2009

2. Workshop Progetti GRID PON Ricerca, Catania 2009
Outline
The CellBE Processor
The MITGCM (Global Circulation Model)
Parallelization of the the 2D Conjugate Gradient routine on the CellBE
(Very) Preliminary performance evaluations
February 11 , 2009
Workshop Progetti GRID PON Ricerca, Catania 2009

3. Workshop Progetti GRID PON Ricerca, Catania 2009
Outline
The CellBE Processor
The MITGCM (Global Circulation Model)
Parallelization of the the 2D Conjugate Gradient routine on the CellBE
(Very) Preliminary performance evaluations
February 11 , 2009
Workshop Progetti GRID PON Ricerca, Catania 2009

4. Workshop Progetti GRID PON Ricerca, Catania 2009
The CRESCO platform
February 11 , 2009
Workshop Progetti GRID PON Ricerca, Catania 2009

5. Workshop Progetti GRID PON Ricerca, Catania 2009
The CellBE processor
February 11 , 2009
Workshop Progetti GRID PON Ricerca, Catania 2009

6. Workshop Progetti GRID PON Ricerca, Catania 2009
The CellBE processor
February 11 , 2009
Workshop Progetti GRID PON Ricerca, Catania 2009

7. Workshop Progetti GRID PON Ricerca, Catania 2009
The CellBE processor
204.8 GB/s
25.6 GFlop/s
February 11 , 2009
Workshop Progetti GRID PON Ricerca, Catania 2009

8. Workshop Progetti GRID PON Ricerca, Catania 2009
The CellBE processor
February 11 , 2009
Workshop Progetti GRID PON Ricerca, Catania 2009

9. Workshop Progetti GRID PON Ricerca, Catania 2009
The CellBE processor
February 11 , 2009
Workshop Progetti GRID PON Ricerca, Catania 2009

10. Workshop Progetti GRID PON Ricerca, Catania 2009
The CellBE processor
February 11 , 2009
Workshop Progetti GRID PON Ricerca, Catania 2009

11. Workshop Progetti GRID PON Ricerca, Catania 2009
Outline
The CellBE Processor
The MITGCM (Global Circulation Model)
Parallelization of the the 2D Conjugate Gradient routine on the CellBE
(Very) Preliminary performance evaluations
February 11 , 2009
Workshop Progetti GRID PON Ricerca, Catania 2009

12. MIT Global Circulation Model
The MITgcm (MIT General Circulation Model) is a numerical model designed for study of the atmosphere, ocean, and climate. Its non-hydrostatic formulation enables it to simulate fluid phenomena over a wide range of scales.
February 11 , 2009
Workshop Progetti GRID PON Ricerca, Catania 2009

13. Workshop Progetti GRID PON Ricerca, Catania 2009
Domain Decomposition
The physical simulation domain is partitioned in 3D tiles. In the example, the domain is split along the x and y dimensions
February 11 , 2009
Workshop Progetti GRID PON Ricerca, Catania 2009

14. Workshop Progetti GRID PON Ricerca, Catania 2009
February 11 , 2009
Workshop Progetti GRID PON Ricerca, Catania 2009

15. Workshop Progetti GRID PON Ricerca, Catania 2009
Outline
The CellBE Processor
The MITGCM (Global Circulation Model)
Parallelization of the the 2D Conjugate Gradient routine on the CellBE
(Very) Preliminary performance evaluations
February 11 , 2009
Workshop Progetti GRID PON Ricerca, Catania 2009

16. Workshop Progetti GRID PON Ricerca, Catania 2009
CG2D Routine
Most demanding kernel of the code;
Solves a linear system of equations Ax=b
Parallelized and demanded to the 8 SPEs
Rewritten in C
Each tile is split in 8 sub-tiles, each managed by one SPE
February 11 , 2009
Workshop Progetti GRID PON Ricerca, Catania 2009

17. Add the borders within the tile …
February 11 , 2009
Workshop Progetti GRID PON Ricerca, Catania 2009

18. Workshop Progetti GRID PON Ricerca, Catania 2009
February 11 , 2009
Workshop Progetti GRID PON Ricerca, Catania 2009

19. Workshop Progetti GRID PON Ricerca, Catania 2009
Outline
The CellBE Processor
The MITGCM (Global Circulation Model)
Parallelization of the the 2D Conjugate Gradient routine on the CellBE
(Very) Preliminary performance evaluations
February 11 , 2009
Workshop Progetti GRID PON Ricerca, Catania 2009

20. Performance evaluation
No specific effort has been devoted (till now) to optimize the code.
Focus to guarantee results correctness
Reported results compare (for a cluster of 8 CellBE processors)
MPI implementation on a cluster of PPE (PowerPC) nodes
MPI implementation on the same PPE cluster + 8 SPE threads per PPE node
February 11 , 2009
Workshop Progetti GRID PON Ricerca, Catania 2009

21. Performance evaluation
Execution time (200 iterations) of CG2D code (>90% of the whole computational effort of the MITgcm code)
MPI MPI+SPE
1.51 sec sec
Speed-up S0 = 3.46
Expected performances upon code optimization and update to new Cell architecture (native Double) ≥ 10xS0
February 11 , 2009
Workshop Progetti GRID PON Ricerca, Catania 2009