On 1/25/07, Ben Tay <zonexo at gmail.com> wrote: > > Hi, > > I was discussing with another user in another forum (cfd-online.com) about > using PETSc in my cfd code. I am now using KSP to solve my momentum and > poisson eqn by inserting values into the matrix. I was told that using PETSc > this way is only for unstructured grids. It is very inefficient and much > slower if I'm using it for my structured grid because I am not exploiting > the regular structure of my grid. > > Is that true? I'm solving flow around airfoil using c-grid. >
If you are using a Cartesian grid, the DA formulation is better. However, this nonsense from people about "massive inefficiency" is just crap. There is a small difference in time which is almost trivial. However, there is a big difference in ease of programming. I am always fascinated how people can magnify small problems in order to preserve their job. So how can I improve? Is it by using DA? I took a glance and it seems quite > complicated. > Wrong glance. Much simpler. Also, is multigrid available in PETSc? Chapter 7 discusses about it but it > seems very brief. Is there a more elaborate tutorial besides that c > examples? > Yes, use DMMG. Much easier with DA. Matt Hope someone can give me some ideas. > > Thank you. > > > -- One trouble is that despite this system, anyone who reads journals widely and critically is forced to realize that there are scarcely any bars to eventual publication. There seems to be no study too fragmented, no hypothesis too trivial, no literature citation too biased or too egotistical, no design too warped, no methodology too bungled, no presentation of results too inaccurate, too obscure, and too contradictory, no analysis too self-serving, no argument too circular, no conclusions too trifling or too unjustified, and no grammar and syntax too offensive for a paper to end up in print. -- Drummond Rennie -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20070126/0a7114b2/attachment.htm>
