/*
	distfunc.c - L1 metric between samples and prototypes

	(c) 2004 Pavel Paclik, pavel@ph.tn.tudelft.nl

	$Id: distfunc.c,v 1.2 2004/03/03 13:13:23 pavel Exp $

  in order to make a MEX file in Matlab use:
  >> mex distfunc.c -lmatlb

*/

#include <mex.h>
#include <memory.h>
#include <string.h>

void mexFunction(
                 int nlhs,       mxArray *plhs[],
                 int nrhs, const mxArray *prhs[]
		 )
{
  double *wp1, *wp2;
  double* pd;
  double dtemp;
  int fc,sc,
    pc; /* number of prototypes */
  mxArray *arr,*arr2, *aout; /* input matrices */

  int i,j,k; /* iterators */
  int is_full_matrix=0; /* flag if we compute the whole sqaure matrix */

  arr=(mxArray*)mlfTranspose(prhs[0]);
  sc=mxGetN(arr);
  fc=mxGetM(arr);

  if( nrhs == 1 ) {
    arr2=arr;
    is_full_matrix=1; /* we may compute just half of the matrix */
  } else {
    arr2=(mxArray*)mlfTranspose(prhs[1]);
  }
   
  pc=mxGetN(arr2);
  if( fc != mxGetM(arr2) ) {
    mexErrMsgTxt("input matrices must have the same number of columns\n");
    return;
  }

  /*
  if( mxGetN(prhs[nrhs-1])==mxGetM(prhs[nrhs-1]) & mxGetN(prhs[nrhs-1])==1 )
    {
      i=(int)*mxGetPr(prhs[nrhs-1]);
      if(i>=0 & i<3) debug_level=i;
      mexPrintf(" debug_level=%d,%d ",debug_level,i);
    }
  */

  /* create output distance matrix */
  aout=mxCreateDoubleMatrix(sc,pc,mxREAL);
  pd=mxGetPr(aout);

  wp1=mxGetPr(arr);
  wp2=mxGetPr(arr2);
  /*  mexPrintf(" %f, %f | %f, %f \n ",wp1[fc],wp1[fc+1],wp2[0],wp2[1]); */

  for(i=0; i<pc; i++) 
    {
      for(j=0; j<sc; j++, pd++) 
	{
	  /* pointers to start of feature vectors */
	  wp1=mxGetPr(arr); wp1+=fc*j;
	  wp2=mxGetPr(arr2); wp2+=fc*i;
	  for( k=0; k<fc; k++, wp1++, wp2++ ) 
	    {
	      dtemp=(*wp1) - (*wp2);
	      /* absolute value */
	      dtemp= dtemp<0.0?-dtemp:dtemp;
	      *pd += dtemp;
	    }
	}
    }

  plhs[0]=aout;

  return;
}