On Wed, Apr 2, 2014 at 9:49 AM, Matthew Knepley <[email protected]> wrote:
> On Wed, Apr 2, 2014 at 8:23 AM, Xiangdong <[email protected]> wrote: > >> Hello everyone, >> >> I have two quick questions about src/snes/examples/tutorials/ex3.c. >> >> 1) In line 150-151, why do we need to call MatSeqAIJSetPreallocation >> before MatMPIAIJSetPreallocation? I found that without the seqaij call, the >> program crashed. However, the mat J we want to create is the mpiaij. >> > > One is used in serial, the other in parallel. Really, you can just call > So depending on the number of processors given in the runtime, either seqaij or mpiaij is not executed, thought both lines are complied. Is it correct? Thank you. Xiangdong > > > http://www.mcs.anl.gov/petsc/petsc-current/docs/manualpages/Mat/MatXAIJSetPreallocation.html > > Matt > > >> 2) In line 390-397, it sets the values of the residue function at the >> boundary. Where do these values come from? In other words, I am not clear >> about ff[0]=xx[0] and ff[xs+xm-1] = xx[xs+xm-1] - 1.0; >> >> Thank you. >> >> Xiangdong >> > > > > -- > What most experimenters take for granted before they begin their > experiments is infinitely more interesting than any results to which their > experiments lead. > -- Norbert Wiener >
