On Sunday 24 January 2010 00:03:41 Garth N. Wells wrote: > Johan Hake wrote: > > On Saturday 23 January 2010 14:55:08 Garth N. Wells wrote: > >> Johan Hake wrote: > >>> On Saturday 23 January 2010 08:42:14 Garth N. Wells wrote: > >>>> Is it correct that behind the scenes that > >>>> > >>>> U0 = Function(V) > >>>> U = Function(V) > >>>> U0.vector()[:] = U.vector()[:] > >>>> > >>>> involves a GenericVector::get(..) call and a GenericVector::set(..) > >>>> call? If so, it isn't ideal since it introduces unnecessary new/delete > >>>> operations and unnecessary copying of data. > >>> > >>> None of GenericVector::get(..) or GenericVector::set(..) are invoked, > >>> see __getslice__ and __setslice__ in la_post.i. > >>> > >>> U0.vector()[:] > >>> > >>> involves > >>> > >>> GenericVector::operator =(..) > >>> > >>> and > >>> > >>> U.vector()[:] > >>> > >>> involves > >>> > >>> GenericVector::copy() > >>> > >>> However the latter is unnecessary as you instead can do: > >>> > >>> U0.vector()[:] = U.vector() > >>> > >>> invoking the assignment operator of U0's vector with U's vector. > >> > >> What happens if I do > >> > >> x = U.vector()[:] > > > > It just triggers the copy method of GenericVector, which is the same > > behavior as for other itterable Python types. > > > >> ? Is x a numpy array? > > > > No you need to call array() to accomplish that. > > OK. What I'm trying to do is > > # Get vectors > u_vec = u.vector()[:] > u0_vec = u0.vector()[:] > v0_vec = v0.vector()[:] > a0_vec = a0.vector()[:]
You should not need to make a copy of the vectors here. > a_vec = 1.0/(2.0*beta)*((u_vec-u0_vec - v0_vec*dt)/(0.5*dt*dt) \ > - (1.0-2.0*beta)*a0_vec) > v_vec = dt*((1.0-gamma)*a0_vec + gamma*a_vec) + v0_vec The expression cause a lot of intermediate vectors, but should work, if beta, gamma and dt are all scalars. > # Update (U0 <- U0) > v0.vector()[:] = v_vec > a0.vector()[:] = a_vec This should work. Johan > I guess I need to call array() to make this work? > > Garth > > > Johan > > > >> Garth > >> > >>> Johan > _______________________________________________ Mailing list: https://launchpad.net/~dolfin Post to : [email protected] Unsubscribe : https://launchpad.net/~dolfin More help : https://help.launchpad.net/ListHelp
