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. > 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? -- Anders
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