On Thu, Mar 08, 2012 at 01:14:40PM +0000, Garth N. Wells wrote: > On 8 March 2012 12:36, Johan Hake <hake....@gmail.com> wrote: > > On Thu, Mar 8, 2012 at 12:40 PM, Garth N. Wells <gn...@cam.ac.uk> wrote: > >> The obvious first step to simplifying dolfin:Array is to minimise its > >> use. Any objections to changing dolfin::Array to std::vector in the > >> GenericFoo abstract linear algebra classes? > > > > It is only GenericVector that uses Array at the moment. Are you > > thinking of changing all double* to std::vector too? > > > >> The consequence on the Python side will be copying of data. I don't > >> think that this is an issue since the interfaces are low-level and > >> only likely used from Python for prototyping or debugging. In such > >> cases, I would expect that other aspects of the Python overhead to > >> swamp to cost of the data copy. > > > > Where it makes sense I am inclined to keep the Array class, and even > > if get,set are low level functionalities they are something that > > potentially will be called many times. > > Will they ever be called many times from Python in production code? > They will be called from low-level C++ code, but using std::vector > will make no difference in this case since it will be passed by > reference. > > > I do not have a benchmark > > telling you that it makes a difference, but from my perspective it > > doesn't make sense to change to std::vector just for the sake of it. > > > > The point is to simplify dolfin::Array. The most important usage is in > GenericFunction::eval, in which case it has fixed length. It was the > usage of dolfin::Array in this context that Joachim picked up the > performance issue. I favour dolfin::Array being as simple as possible > and targeted to handle the call-back type situation in > GenericFunction::eval both efficiently and safely (from both Python > and C++).
I agree completely with this. My take is that there is a set of operations that we should allow for convenience (one is matrix random access that we've discussed many times before) and they don't need to be very efficient. But I don't know the implications of removing the get/set operations for the SWIG layer. -- Anders > Garth > > > Johan > > > >> Garth > >> > >> _______________________________________________ > >> 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
