Hi there, I am tuning our 3D FEM CFD code written with PETSc. The code doesn't scale very well. For example, with 8 processes on a linux cluster, the speedup we achieve with a fairly large problem size(million of elements) is only 3 to 4 using the Congugate gradient solver. We can achieve a speed up of a 6.5 using a GMRes solver but the wall clock time of a GMRes is longer than a CG solver which indicates that CG is the faster solver and it scales not as good as GMRes. Is this generally true?
I then went to the examples and find a 2D example of KSPSolve (ex2.c). I let the code ran with a 1000x1000 mesh and get a linear scaling of the CG solver and a super linear scaling of the GMRes. These are both much better than our code. However, I think the 2D nature of the sample problem might help the scaling of the code. So I would like to try some 3D example using the KSPSolve. Unfortunately, I couldn't find such an example either in the src/ksp/ksp/examples/tutorials directory or by google search. There are a couple of 3D examples in the src/ksp/ksp/examples/tutorials but they are about the SNES not KSPSolve. If anyone can provide me with such an example, I would really appreciate it. Thanks a lot. Shi ____________________________________________________________________________________ Finding fabulous fares is fun. Let Yahoo! FareChase search your favorite travel sites to find flight and hotel bargains. http://farechase.yahoo.com/promo-generic-14795097