[Numpy-discussion] SWIG and numpy.i
Bill Spotz
wfspotz@sandia....
Wed Mar 25 08:03:16 CDT 2009
Kevin,
In this instance, the best thing is to write a wrapper function that
calls your matSum() function, and takes a double* rather than a
double**. You can %ignore the original function and %rename the
wrapper so that the python interface gets the name you want.
On Mar 25, 2009, at 7:39 AM, Kevin Françoisse wrote:
> Thanks Bill, it helps me a lot ! My function works fine now.
>
> But I encounter an other problem. This time with a NumPy array of 2
> dimensions.
>
> Here is the function I want to use :
>
> /****************/
> double matSum(double** mat, int n, int m){
> int i,j;
> double sum = 0.0;
> for (i=0;i<n;i++){
> for (j=0;j<m;j++){
> sum += mat[i][j];
> }
> }
> return sum;
> }
> /****************/
>
> I supposed that the typemaps to use is the following :
>
> %apply (double* IN_ARRAY2, int DIM1, int DIM2) {(double** mat, int
> n, int m)};
>
> But it is not working. Of course, my typemaps assignement is not
> compatible with my function parameters. I tried several ways of
> using a two dimensional array but I'm not sure what is the best way
> to do it ?
>
> Thanks
>
> ---
> Kevin Françoisse
> Ph.D. at Machine Learning Group at UCL
> Belgium
> kevin.francoisse@uclouvain.be
>
> On Tue, Mar 24, 2009 at 6:13 PM, Bill Spotz <wfspotz@sandia.gov>
> wrote:
> Kevin,
>
> You need to declare vecSum() *after* you %include "numpy.i" and use
> the %apply directive. Based on what you have, I think you can just
> get rid of the "extern double vecSum(...)". I don't see what
> purpose it serves. As is, it is telling swig to wrap vecSum()
> before you have set up your numpy typemaps.
>
>
> On Mar 24, 2009, at 10:33 AM, Kevin Françoisse wrote:
>
> Hi everyone,
>
> I have been using NumPy for a couple of month now, as part of my
> research project at the university. But now, I have to use a big C
> library I wrote myself in a python project. So I choose to use SWIG
> for the interface between both my python script and my C library. To
> make things more comprehensible, I wrote a small C methods that
> illustrate my problem:
>
> /* matrix.c */
>
> #include <stdlib.h>
> #include <stdio.h>
> /* Compute the sum of a vector of reals */
> double vecSum(int* vec,int m){
> int i;
> double sum =0.0;
>
> for(i=0;i<m;i++){
> sum += vec[i];
> }
> return sum;
> }
>
> /***/
>
> /* matrix.h */
>
> double vecSum(int* vec,int m);
>
> /***/
>
> /* matrix.i */
>
> %module matrix
> %{
> #define SWIG_FILE_WITH_INIT
> #include "matrix.h"
> %}
>
> extern double vecSum(int* vec, int m);
>
> %include "numpy.i"
>
> %init %{
> import_array();
> %}
>
> %apply (int* IN_ARRAY1, int DIM1) {(int* vec, int m)};
> %include "matrix.h"
>
> /***/
>
> I'm using a python script to compile my swig interface and my C
> files (running Mac OS X 10.5)
>
> /* matrixSetup.py */
>
> from distutils.core import setup, Extension
> import numpy
>
> setup(name='matrix', version='1.0', ext_modules
> =[Extension('_matrix', ['matrix.c','matrix.i'],
> include_dirs = [numpy.get_include(),'.'])])
>
> /***/
>
> Everything seems to work fine ! But when I test my wrapped module in
> python with an small NumPy array, here what I get :
>
> >>> import matrix
> >>> from numpy import *
> >>> a = arange(10)
> >>> matrix.vecSum(a,a.shape[0])
> Traceback (most recent call last):
> File "<stdin>", line 1, in <module>
> TypeError: in method 'vecSum', argument 1 of type 'int *'
>
> How can I tell SWIG that my Integer NumPy array should represent a
> int* array in C ?
>
> Thank you very much,
>
> Kevin
> <ATT00002.txt>
>
> ** Bill Spotz **
> ** Sandia National Laboratories Voice: (505)845-0170 **
> ** P.O. Box 5800 Fax: (505)284-0154 **
> ** Albuquerque, NM 87185-0370 Email: wfspotz@sandia.gov **
>
>
>
>
>
>
>
** Bill Spotz **
** Sandia National Laboratories Voice: (505)845-0170 **
** P.O. Box 5800 Fax: (505)284-0154 **
** Albuquerque, NM 87185-0370 Email: wfspotz@sandia.gov **
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