On Wed, Apr 2, 2014 at 9:50 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. >> >> 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; >> > > These are just the BC we choose. > The exact solution used in the code is u=x^3. The thing not clear to me is how this is translated to the boundary conditions I mentioned above. More like a formulation question, in fact. Thank you. Xiangdong > > Matt > > >> 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 >
