Anders Logg wrote: > We still haven't decided on the correct strategy for choosing the > degree of an unspecified element. > > What we have now looks at the total degree of the form and then sets > the degree accordingly. This doesn't really work weoull and the reason > is quite simple: We can't figure out the total degree correctly if we > don't know the degree of the coefficient. > > So my new suggestion is the following. We simply scan all elements in > the form with specified degrees and set the degree to the maximum > degree among the elements. >
Or should it be the maximum degree of the test and trial functions? Do you take into accout derivatives, e.g. for w*dot(grad(v), grad(u))*dx would w be of the same order as v and u, or one order lower? Garth > Here are some use cases: > > 1. v*f*dx > > If v is an element of degree q, then the degree for the approximation > of f is set to q. > > For quadrature elements, this means thatd we get a quadrature error in > the integral of order q + 1 which in many cases is the same as the > convergence of the finite element method. > > For Lagrange elements, we get an interpolation error when > approximating f of degree q + 1 so the situation is the same. > > 2. v*f*g*dx > > Same as above here if f and g have unspecified degrees. But if f or g > should happen to have a degree higher than q, than that degree will be > used for the other coefficient if unspecified. > > I'll go ahead and make this change in FFC. It's rather easy to change > the strategy and FFC is being very verbose about the choices it makes, > at least until we have settled on an acceptable strategy. > > -- > Anders > > > ------------------------------------------------------------------------ > > _______________________________________________ > Mailing list: https://launchpad.net/~ffc > Post to : [email protected] > Unsubscribe : https://launchpad.net/~ffc > More help : https://help.launchpad.net/ListHelp _______________________________________________ Mailing list: https://launchpad.net/~ffc Post to : [email protected] Unsubscribe : https://launchpad.net/~ffc More help : https://help.launchpad.net/ListHelp
