Johan Hake wrote: > On Tuesday 01 December 2009 11:21:00 Garth N. Wells wrote: >> Johan Hake wrote: >>> On Tuesday 01 December 2009 11:06:43 you wrote: >>>> 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. >>>> Can we just call it Array? It will be visible in the C++ interface (e.g. >>>> in eval) so it would be good to have a nice name. >>> Agree. >>> >>>>> I have created a blueprint: >>>>> >>>>> https://blueprints.launchpad.net/dolfin/+spec/array-typemaps >>>> I'll add something. I was thinking already about this. With a smart >>>> pointer to the underlying data we should be to devise an elegant memory >>>> model and be able to tell an Array object when it does and doesn't own >>>> the data upon construction, and be able to change during execution. >>> Sounds fancy. >>> >>>>> 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? >>>> The fast fix would be revert back to the >>>> >>>> eval(double*, std::vector<double>&) >>>> >>>> interface. No point wasting time on typemaps for std::vector if we're >>>> not going to use them. >>> Fell free to make this change, I have a fool proof plan for the other >>> temporary fix though. No new typemaps, just reusing old ones. >> OK, we need to make a decision. >> >> Option 1: Revert changes to eval. >> >> Option 2: Get SWIG working with the eval(std::vector<double>&, const >> std::vector<double>&) interface. >> >> What's it going to be? I'm inclined to Option 1 since it requires no >> work and it's been well tested. > > Isn't the amount of files that are touched with option 1 much larger (all > cpp/demos)?
Yes, but it's easy. I can just selectively revert files. But if you do the changes feel free. I can take a look at it this > evening if there's something left to do. The new expression.py should at > least > still be working I think, only compile_expressions.py needs an update. > Yes. Perhaps you could push your std:vector work to a branch so we have a record of it and don't go re-inventing the wheel in the future. Garth > Johan > >> Garth >> >>> Johan >>> >>>> Garth >>>> >>>>> -- >>>>> Anders _______________________________________________ Mailing list: https://launchpad.net/~dolfin Post to : [email protected] Unsubscribe : https://launchpad.net/~dolfin More help : https://help.launchpad.net/ListHelp
