On Tuesday 01 December 2009 10:49:27 Anders Logg wrote: > On Tue, Dec 01, 2009 at 09:59:18AM -0800, Johan Hake wrote: > > On Tuesday 01 December 2009 00:45:50 Anders Logg wrote: > > > Would it help to add a new class on the C++ side that is used only for > > > passing array data back and forth between C++ and Python? We have had > > > this before (SimpleArray) and it would be fairly easy to extend the > > > C++ with extra functions in the interface that use SimpleArray instead > > > of std::vector. > > > > > > Then perhaps we can have one single typemap that hits SimpleArray > > > everywhere and converts it to a NumPy array. > > > > Yes, something in that direction is what I had in mind. In addition we > > could also add a foo.array() function to get a NumPy view from this > > class. This would be nice when we do not want to have all the > > communication through typemaps, but actually using the SimpleArray in > > Python as return argument from some function that wants to resize the > > array. > > > > We would also need some stuff to handle memory management. > > > > I see two fundamental ways such a class could be used: > > 1) A replacement for the previous use of double/uint/int*, now > > std::vector 2) A replacement for communication using std::vector where > > resize flexibility is needed. > > > > I think 1, speaks for it self. 2 is where we need to resize any passed > > vector. This goes for GenericMatrix.getrow, foo.intersection, > > GenericFunction.comput_vertex_values. > > > > > And the work would be to add the extra stuff on the C++ side. The > > > advantage would be less complex wrapper code and that Garth and I > > > are capable of handling the complexities on the C++ side. > > > > Yes this must be a goal. I agree that the present SWIG situation has > > grown out of hands. > > > > > But what I don't understand is why it would be easier to write a > > > typemap for SimpleArray than for std::vector. Both of them use > > > contiguous memory. > > > > Yes, but in std::vector it is now way, I suppose, to prevent a vector to > > delete its data when it goes out of scope. This is necessary in a typical > > in typemap. > > ok, let's create a very flexible array class that is targeted at > simple communication between C++ and Python/NumPy. We had a class > before named SimpleArray. We might call it NumPyArray or PythonArray. > > I have created a blueprint: > > https://blueprints.launchpad.net/dolfin/+spec/array-typemaps > > We can fill out the details together.
Good > > I will fix the interface of getrow this evening. I was about to do it > > yesterday, but instead I got grumpy :) But a good night sleep makes > > wonders! > > Good! :-) > > Will you make a fast/temporary fix so that we can get ready for a > release of 0.9.5 and then we can move the PythonArray implementation > to a future release? Yes, that's the plan. Johan > -- > Anders > _______________________________________________ Mailing list: https://launchpad.net/~dolfin Post to : [email protected] Unsubscribe : https://launchpad.net/~dolfin More help : https://help.launchpad.net/ListHelp
