On Fri, Oct 20, 2017 at 9:23 AM, Emil Constantinescu <[email protected]> wrote:
> On 10/20/17 7:57 AM, Matthew Knepley wrote: > >> I am confused by some of the terminology in TS. At the top level, >> IFunction appears to mean the entire equation >> >> F(u, u_t, x) = 0 >> > > Matt, page 141 of the manual: F(t, u, u_t) = G(t, u), and not zero on the > RHS side. To make the interface general we allow internally for F:= F(t, u, > u_t) - G(t, u) and then F=0. > This is not "internal". Its the toplevel interface: https://bitbucket.org/petsc/petsc/src/63ae3ecac3af8ce782273a76ad4152cddc2fd80a/src/ts/interface/ts.c?at=master&fileviewer=file-view-default#ts.c-884 It computes F - G. Matt > Emil > > PS: Manual: PETSc 3.8 September 26, 2017 > > However, this appears to mean something different than ifunction at the >> function pointer level. Inside TSCompiteIFunction(), it uses both ifunction >> and rhsfunction. This makes it hard to understand how composition works. >> TSComputeRHS() is called inside TSComputeIFunction(), so if we want to >> reuse vectors it should not initialize the vector, but it seems like >> TSComputeIFunction() should initialize the vector since >> TSComputeIFunctionLocal() does. >> >> What guarantees about initialization should we have? >> >> Matt >> >> -- >> 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 >> >> https://www.cse.buffalo.edu/~knepley/ <http://www.caam.rice.edu/~mk51/> >> > -- 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 https://www.cse.buffalo.edu/~knepley/ <http://www.caam.rice.edu/~mk51/>
