Thank you. But my code has 10 calls to KSPSolve of three different linear systems at each time update. Should I strip it down to a single KSPSolve so that it is easier to analysis? I might have the code dump the Matrix and vector and write another code to read them into and call KSPSolve. I don't know whether this is worth doing or should I just send in the messy log file of the whole run. Thanks for any advice.
Shi --- Barry Smith <bsmith at mcs.anl.gov> wrote: > > Shi, > > There is never a better test problem then your > actual problem. > Send the results from running on 1, 4, and 8 > processes with the options > -log_summary -ksp_view (use the optimized version of > PETSc (running > config/configure.py --with-debugging=0)) > > Barry > > > On Fri, 9 Feb 2007, Shi Jin wrote: > > > 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 > > > > > > ____________________________________________________________________________________ 8:00? 8:25? 8:40? Find a flick in no time with the Yahoo! Search movie showtime shortcut. http://tools.search.yahoo.com/shortcuts/#news
