On Tue, Feb 14, 2017 at 8:55 AM, Emil Constantinescu <emcon...@mcs.anl.gov> wrote:
> On 2/14/17 6:53 AM, Matthew Knepley wrote: > >> >> Explicit methods use only RHSFunction and ignore IFunction, so in >> your case, if you change TS type to rk and ssp at run time, you are >> actually solving u_t = G(t,u). If RHSFunction is not provided, PETSc >> will assume the RHS is zero (u_t=0). >> >> >> I do not agree with this. I thought our aim was to support users >> comparing explicit with implicit with semi-implicit. This breaks that >> model completely. >> > > Matt, all RHSFunction can be turned into IFunction but not the other way > around. Explicit TS solvers cannot deal with all forms of IFunction and > providing support for classifying them may be burdensome and difficult to > scale. I think it's more lucrative to improve the documentation. I see that is it not one-to-one, but its a pattern I think a lot of people will want, and one of the most common things people ask is "when does implicit beat explicit?". We should think about ways to make this easier. Matt > > Emil > > -- 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