On 20 May 2011 09:11, James Avery <question158...@answers.launchpad.net> wrote: > Question #158285 on DOLFIN changed: > https://answers.launchpad.net/dolfin/+question/158285 > > James Avery posted a new comment: > Hi Anders, > > Thanks a lot! That works. However, a quick follow-up question: It seems > to me that it should be possible to compute the derivatives of a finite- > element function f in a more efficient manner, since we have f's > expansion in terms of basis functions that can be differentiated, > although I have not been able to find out how these are accessed in > DOLFIN.
You can get the finite element of the function and call the function evaluate_basis_derivatives on that. Kristian > Is it strictly necessary to assemble and solve a new linear system to > obtain a gradient? The reason I'm asking is, that the bottleneck in my > application is due to the matrices describing the linear systems (with > mesh size of up to a couple million cells). Thus assembling a matrix (or > storing a precalculated one) and solving a linear system is a fairly > large operation. Is there perhaps a shortcut for just computing the > function derivatives with DOLFIN? This is what the project() function in PyDOLFIN does and you're right, that it might not be efficient for some applications. Kristian > Thank you again for your help! > > -- > You received this question notification because you are a member of > DOLFIN Team, which is an answer contact for DOLFIN. > > _______________________________________________ > Mailing list: https://launchpad.net/~dolfin > Post to : dolfin@lists.launchpad.net > Unsubscribe : https://launchpad.net/~dolfin > More help : https://help.launchpad.net/ListHelp > _______________________________________________ Mailing list: https://launchpad.net/~dolfin Post to : dolfin@lists.launchpad.net Unsubscribe : https://launchpad.net/~dolfin More help : https://help.launchpad.net/ListHelp
