Interfacing Ada with C
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From: Dmitry A. Kazakov on 24 Jul 2010 12:44 On Sat, 24 Jul 2010 04:57:53 -0700 (PDT), Ada novice wrote: > So in essence I'm looking for examples which illustrate how to pass > some data (e.g a matrix) from Ada to C, Since C does not have arrays, especially 2D ones, you will have some custom representation on the C side. It means that examples of bindings (there are plenty of) won't help you unless you understand how you describe a C-compatible object in Ada. > do some computations on the > matrix and return the results to the Ada environment. Even more so, because C cannot return a compound object. Different C libraries use different tricks to work around this. I would propose reading RM B.3 and B.3.2. Another thing you have to understand is the issue of flat arrays vs. arrays with a dope. The latter cannot be used with C. Provided you know C well, the rest is simple. -- Regards, Dmitry A. Kazakov http://www.dmitry-kazakov.de
From: Ada novice on 24 Jul 2010 13:58 On Jul 24, 6:38 pm, Simon Wright <si...(a)pushface.org> wrote: > but on a Windows machine it'll be something li > <install-dir>\<gnat-release>\lib\gcc\<architecture>\<gcc-release>\adainclude\a-ngrear.ad[sb] > > This will lead you to System.Generic_Real_BLAS (s-gerebl.ad[sb]) and > System.Generic_Real_LAPACK (s-gerela.ad[sb]), which are interfaces to > the corresponding external libraries. > > Not sure that these will fit your 'simple' criterion, though! > > --S Thanks. I've been able to locate these files under GNAT on my Windows machine and read them. For eigensystems operations, only symmetric and hermitian (complex-symmetric) matrices are allowed. I would like however to be able to deal with a general non-symmetric matrix and this I believe is not possible right now with Ada. YC
From: Ada novice on 24 Jul 2010 14:04 On Jul 24, 6:44 pm, "Dmitry A. Kazakov" <mail...(a)dmitry-kazakov.de> wrote: > Since C does not have arrays, especially 2D ones, you will have some custom > representation on the C side. It means that examples of bindings (there are > plenty of) won't help you unless you understand how you describe a > C-compatible object in Ada. Thanks for the "warnings". One way that I'm thinking is to write the elements of the matrix sequentially into a file in Ada, read them into C, put them into a matrix in C, do the appropriate computations in C (with the IMSL C library), write the output in C in a file, and finally importing them back into Ada again for further processing. Of course, having several read-write operations is not computationally time-efficient but this is a modest way to get starting. I know C at a basic level and I'm not not an extensive user. YC
From: Dmitry A. Kazakov on 24 Jul 2010 15:16 On Sat, 24 Jul 2010 11:04:18 -0700 (PDT), Ada novice wrote: > On Jul 24, 6:44�pm, "Dmitry A. Kazakov" <mail...(a)dmitry-kazakov.de> > wrote: > >> Since C does not have arrays, especially 2D ones, you will have some custom >> representation on the C side. It means that examples of bindings (there are >> plenty of) won't help you unless you understand how you describe a >> C-compatible object in Ada. > > Thanks for the "warnings". One way that I'm thinking is to write the > elements of the matrix sequentially into a file in Ada, read them into > C, put them into a matrix in C, do the appropriate computations in C > (with the IMSL C library), write the output in C in a file, and > finally importing them back into Ada again for further processing. Of > course, having several read-write operations is not computationally > time-efficient but this is a modest way to get starting. I know C at a > basic level and I'm not not an extensive user. Why not to call IMSL directly from Ada? I looked shortly here http://www.vni.com/products/imsl/c/TechSpecs/CNLspecs3MatrixStorage.php it looks well documented and fairly designed. There should be no problem to call it from Ada. -- Regards, Dmitry A. Kazakov http://www.dmitry-kazakov.de
From: tmoran on 24 Jul 2010 20:22
> On Jul 24, 6:44=A0pm, "Dmitry A. Kazakov" <mail...(a)dmitry-kazakov.de> > wrote: > > > Since C does not have arrays, especially 2D ones, you will have some cust= > om > > representation on the C side. It means that examples of bindings (there a= > re > > plenty of) won't help you unless you understand how you describe a > > C-compatible object in Ada. > > > Thanks for the "warnings". One way that I'm thinking is to write the > elements of the matrix sequentially into a file in Ada, read them into > C, put them into a matrix in C, do the appropriate computations in C > (with the IMSL C library), write the output in C in a file, and > finally importing them back into Ada again for further processing. Why do somersaults when you can just walk a few steps. As Dmitry says, it really does depend on just what you are supposed to pass to the C routine. For instance, there's a very fast C routine to calculate an FFT of a 256 element complex vector. Using type Complex_Vectors is array(Integer range <>) of Ada.Numerics.Complex_Types.Complex; subtype Complex_256s is Complex_Vectors(1 .. 256); procedure fftc4_256(V : in out Complex_256s); pragma import(c, fftc4_256,"fftc4_256"); it can be called with X : Complex_256s; ... fftc4(X); Hard to get any simpler. If the C routine wants a pointer to an array of pointers to rows, plus a couple of dimensions, that's a little harder. But if the array is stored simply, and C expects the elements laid out the same way as Ada, you can probably just pass in a pointer to the first element in the array: type Matrix_Type is array(Integer Range <>, Integer range <>) of aliased Ada.Numerics.Complex_Types.Complex; type Pointer_To_Element is access all Ada.Numerics.Complex_Types.Complex; procedure C_Routine(M : in Pointer_To_Element; Height, Width : in Interfaces.C.Unsigned); pragma import(C, C_Routine, "c_routine"); M : Matrix_Type(1 .. 10, 0 .. 100); ... C_Routine(M(M'first(1), M'first(2))'access, Height => M'length(1), Width => M'length(2)); For a whole lot of examples of Ada calling C, download the source for CLAW (Class Library for Ada Windows) from www.rrsoftware.com |