From help-request at octave dot org Tue Mar 22 20:33:07 2005
Subject: Re: Mex files oct.h and mxGetDimensions
From: Paul Kienzle <pkienzle at users dot sourceforge dot net>
To: Carine Simon <csimon at utm dot csic dot es>
Cc: help at octave dot org
Date: Tue, 22 Mar 2005 21:40:50 -0500

At the time I wrote them, there were no n-dimensional matrices
in octave, and so I didn't implement them.  You are welcome to
extend the underlying code to use n-D arrays internally.

Note that the current code was a quick hack which served my needs
at the time.  Ideally it should be rewritten in a way that allows
you to directly reference the data in Octave arrays rather than
making unnecessary copies.  This is not possible in general since
Octave uses interleaved real-imaginary values for complex but
matlab uses separate real and imaginary arrays, but with some lazy
in-place transposes you can minimize the performance hit.

- Paul

On Mar 22, 2005, at 12:00 PM, Carine Simon wrote:

>
> Hi,
>
> I've got some troubles trying to use some mex files. The first one is 
> that if I
> include oct.h file, it cannot compile as it doesn't find some files 
> such as
> cassert. In fact, I think this is because include files of octave are 
> under
> /usr/local/include whereas C and C++ ones are under /usr/include. But 
> I don't
> know how to precise where to find libraries.
>
> Well, I can still compile one of my functions without the oct.h. But I 
> can't use
> it as it doesn't find mxGetDimensions.
> To try to be a bit more clear, I send you below the function I've 
> tested:
>
> /********************************************************************/
> /********************************************************************/
>
> /*#include "oct.h"*/
> #include "mex.h"
> #include <math.h>
>
> void normalitzar(double *x1, double *y1, const int *dim_array) {
>
> 	int i, j;
> 	double tmp;
> 	double *x2, *x3, *y2, *y3;
>
> 	x2 = x1 + dim_array[0]*dim_array[1];
> 	x3 = x2 + dim_array[0]*dim_array[1];
> 	
> 	y2 = y1 + dim_array[0]*dim_array[1];
> 	y3 = y2 + dim_array[0]*dim_array[1];
>
> 	for( i = 0; i < dim_array[0]; i++) {
> 		for( j = 0; j < dim_array[1]; j++) {
>             if (tmp = sqrt( *x1**x1 + *x2**x2 + *x3**x3 )) {;
> 			    *y1++ = *x1++ / tmp;
> 			    *y2++ = *x2++ / tmp;
> 			    *y3++ = *x3++ / tmp;
>             } else {
>                 *y1++ = *x1++;
> 			    *y2++ = *x2++;
> 			    *y3++ = *x3++;
>             }
> 		}
> 	}
> }
>
>
> /* The gateway routine */
> void mexFunction(int nlhs, mxArray *plhs[],
> 				 int nrhs, const mxArray *prhs[])
> {
> 	double *y, *x;
> 	int elements, number_of_dims;
> 	const int *dim_array;
> 	
>   /*  Check for proper number of arguments. */
>   /* NOTE: You do not need an else statement when using
>      mexErrMsgTxt within an if statement. It will never
>      get to the else statement if mexErrMsgTxt is executed.
>      (mexErrMsgTxt breaks you out of the MEX-file.)
>   */
> 	if (nrhs != 1)
> 		mexErrMsgTxt("One inputs required.");
> 	
> 	/* Check data type of input argument. */
> 	if (!(mxIsDouble(prhs[0]))) {
> 		mexErrMsgTxt("Input array must be of type double.");
> 	}
>
> 	/* Get the number of elements in the input argument. */
> 	elements = mxGetNumberOfElements(prhs[0]);
>
> 	/* Create a pointer to the input matrix x. */
> 	x = mxGetPr(prhs[0]);
>
> 	/* Get the number of dimensions in the input argument.
>        Allocate the space for the return argument */
> 	number_of_dims = mxGetNumberOfDimensions(prhs[0]);
> 	dim_array = mxGetDimensions(prhs[0]);
> 	plhs[0] = mxCreateDoubleMatrix(elements, number_of_dims, mxREAL);
>
> 	/* Create a C pointer to a copy of the output matrix. */
> 	y = mxGetPr(plhs[0]);
>
> 	/* Get the number of dimensions in the input argument. */
> 	dim_array = mxGetDimensions(prhs[0]);
>
> 	mxSetDimensions(plhs[0], dim_array, number_of_dims);
>
> 	/* Call the C subroutine. */
> 	normalitzar(x, y, dim_array);
> }
>
> To test it, a matrix like X=rand(100,100,3) should be passed.
>
> Thanks,
> Carine.
>
> -------------------------------------------------
> This mail sent through IMP: http://horde.org/imp/
>
>
>
> -------------------------------------------------------------
> Octave is freely available under the terms of the GNU GPL.
>
> Octave's home on the web:  http://www.octave.org
> How to fund new projects:  http://www.octave.org/funding.html
> Subscription information:  http://www.octave.org/archive.html
> -------------------------------------------------------------
>



-------------------------------------------------------------
Octave is freely available under the terms of the GNU GPL.

Octave's home on the web:  http://www.octave.org
How to fund new projects:  http://www.octave.org/funding.html
Subscription information:  http://www.octave.org/archive.html
-------------------------------------------------------------