On Fri, Dec 9, 2016 at 11:45 AM, Derek Gaston <[email protected]> wrote:
> Is there a way to tell SNES to simultaneously compute both the residual > and the Jacobian in one callback? > > My code can compute both simultaneously and it will be more efficient > (think FE where you can reuse the shape-functions, variables, material > properties, etc. for both residual and Jacobian computation). In addition, > I also have automatic differentiation as an option which _definitely_ > computes both efficiently (and actually computes residuals, by themselves, > much slower). > > I was thinking that I may just save off the Jacobian whenever the initial > residual computation is asked for by > It is a reasonable way. But there is no a straight way to determine when you should evaluate Jacobian especially when you use a matrix-free matter. > SNES... and then just return that Jacobian when SNES asks for it. This > may be a bit dicey though as SNES can ask for residual computations at many > different points during the solve. > > Thanks for any help! > > Derek >
