vl_tpsumx.c

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/* file:        tpsumx.c
** author:      Andrea Vedaldi
** description: vl_tpsumx - MEX definition
**/

/*
Copyright (C) 2007-12 Andrea Vedaldi and Brian Fulkerson.
All rights reserved.

This file is part of the VLFeat library and is made available under
the terms of the BSD license (see the COPYING file).
*/

#include <mexutils.h>

#include <stdlib.h>
#include <math.h>

#define getM(arg) mxGetM(in[arg])
#define getN(arg) mxGetN(in[arg])
#define getPr(arg) mxGetPr(in[arg])

void
mexFunction(int nout, mxArray *out[],
            int nin, const mxArray *in[])
{
  enum { X=0,Y } ;
  enum { U } ;

  int NP, NCP ;
  int i,j ;
  double *X_pt, *Y_pt, *U_pt ;
#undef small
  const double small = 2.220446049250313e-16 ;

  /* -----------------------------------------------------------------
   *                                               Check the arguments
   * -------------------------------------------------------------- */
  if (nin != 2) {
    vlmxError(vlmxErrNotEnoughInputArguments, NULL) ;
  } else if (nout > 1) {
    vlmxError(vlmxErrTooManyOutputArguments, NULL) ;
  }

  if(!vlmxIsMatrix(in[X], 2, -1)) {
    mexErrMsgTxt("X must be a 2xNP real matrix") ;
  }

  if(!vlmxIsMatrix(in[Y], 2, -1)) {
    mexErrMsgTxt("Y must be a 2xNCP real matrix") ;
  }

  NP  = getN(X) ;
  NCP = getN(Y) ;

  X_pt = getPr(X);
  Y_pt = getPr(Y) ;

  /* Allocate the result. */
  out[U] = mxCreateDoubleMatrix(NP, NCP, mxREAL) ;
  U_pt = mxGetPr(out[U]) ;

  /* -----------------------------------------------------------------
   *                                               Check the arguments
   * -------------------------------------------------------------- */
  for(j = 0 ; j < NCP ; ++j) {
    double xcp = *Y_pt++ ;
    double ycp = *Y_pt++ ;
    for(i = 0 ; i < NP ; ++i) {
      double dx = *X_pt++ - xcp ;
      double dy = *X_pt++ - ycp ;
      double r2 = dx*dx + dy*dy ;
      *U_pt++ = (r2 <= small) ? 0 : r2 * log (r2) ;
    }
    X_pt -= 2*NP ;
  }
}