Hi Guy, Thanks again for raising these issues. This is the status as I see it
Presently I am trying to use the mapping between Theano and SymPy > (sympy.printing.theanocode theano_function) to make my callable functions > and take advantage of the optimization routines. I have two major problems > and a few questions: > > 1st major problem: Though piecewise functions exist in SymPy > (sympy.functions.elementary.piecewise) there is no counterpart in Theano. > Looking at the source of the inspiration for theanocode ( > https://github.com/nouiz/theano_sympy/ graph_translation.py) I see > that some of the SymPy equivalents were defined as lambda functions. Is > there an equivalent way to add Theano conditional expressions wrapped into > a function to add to the mapping dictionary in theanocode.py? > This is in https://github.com/sympy/sympy/pull/2366 and should hopefully soon be merged. > 2nd major problem: Similar to the problem above in that I am not sure that > the Theano counterpart is; some of the terms that I use are interpolated > functions (with one ODE variable as input) that we have wrapped > symbolically while providing a numerical implementation (so that symbolic > derivatives can be made, resulting in their own interpolations). Is it > possible to recreate the interpolation function as a Theano operation for > use within the system of ODEs? > I'm not sure I fully understand this piece. Is it possible to define your interpolation scheme with lower-level operators such as with Piecewise and polynomials? What is your interpolation scheme? Remain questions: > I presently have to flatten my input to theano_function to a list of > expressions and then wrap to return to a form (Jacobian is a matrix not a > vector); is it possible to have a matrix of different expressions as an > input to theano_function with a vector output? > Jason answered this I think. In the dev version theano_function should be able to take SymPy matrices as inputs. See the description of this PR for an example https://github.com/sympy/sympy/pull/2013 I know that a huge amount of Theano speed up is due to parallelization of > matrix operations (which I do not have), should I be focusing on SymPy > Autowrap/Ufuncify or my own code generation instead of trying to get Theano > to play nicely? > I find your engagement of the SymPy-Theano connection valuable and am happy to support it. I think you'll find autowrap/ufuncify possibly more mature but less well supported. > Stupid questions: > Does sympy.printing.theanocode.theano_function automatically optimize the > compiled graph? > Answered: yes > Minor comment: > Perhaps unnecessary for most uses of the theano_function, but I needed to > modify function inputs so as to be able to use the keyword argument > 'on_unused_input=ignore' as opposed to 'raise' so that I did not need to > have all symbols in all equations. This may be avoided by having the unused > symbols somehow (I don't know how) included in each expression. > Answered: In PR https://github.com/sympy/sympy/pull/2358 > With regards to using an externally defined theano graph or op (theano wrapped sympy implementation), how would one pass them to theano_function? It feels as though it would be analogous to the autowrap helpers argument, or would this be an issue of merging graphs before calling theano.function? If I can understand this step, I feel as though both of my problems would be solvable (a wrapping of a piecewise along with a wrapping of an interpolated function) Answered: use theano_code > With the example above of having an implemented function in some expression in sympy, assuming one can write the c-code equivalent, how would one link the c-code to the codegen process as opposed to having codegen generate it? I don't think we can do this. If you have C implementations of operations within SymPy that aren't yet supported we'd love help with this. See https://github.com/sympy/sympy/pull/2369 In general let us know how you're doing with this project and what is keeping you from making progress. -Matt -- You received this message because you are subscribed to the Google Groups "sympy" group. To unsubscribe from this group and stop receiving emails from it, send an email to sympy+unsubscr...@googlegroups.com. To post to this group, send email to sympy@googlegroups.com. Visit this group at http://groups.google.com/group/sympy. For more options, visit https://groups.google.com/groups/opt_out.
