/* -------------------------------------------------------------------- Evaluation of kernel functions: linear, poly, rbf, sigmoidal. About: Statistical Pattern Recognition Toolbox (C) 1999-2003, Written by Vojtech Franc and Vaclav Hlavac <a href="http://www.cvut.cz">Czech Technical University Prague</a> <a href="http://www.feld.cvut.cz">Faculty of Electrical Engineering</a> <a href="http://cmp.felk.cvut.cz">Center for Machine Perception</a> Modifications: 4-may-2004, VF 4-June-2003, VF 12-November-2001, V.Franc, sigmoid kenel 22-September-2001, V. Franc, created.-------------------------------------------------------------------- */#include "mex.h"#include "matrix.h"#include <math.h>#include <string.h>/* --- Global variables --------------------------------------------- */double *dataA;      /* pointer at the fist patterns */double *dataB;      /* pointer at the second patterns */long dim;           /* dimension of patterns */int ker;            /* kernel id (0 - linear, 1 - polynomial,                        2 - rbf, 3 - sigmoid */double *arg1;       /* kernel argument */long ker_cnt;       /* number of cernel evaluations */char *kernel_name[] = {"linear","poly","rbf","sigmoid"};/* ------------------------------------------------------------------- Computes dot product of a-th and b-th vector. c = a'*b------------------------------------------------------------------- */double dot_prod( long a, long b){   double c = 0;   long i;   for( i = 0; i < dim; i++ ) {      c += *(dataA+(a*dim)+i) * *(dataB+(b*dim)+i);   }   return( c );}/* ------------------------------------------------------------------- Computes dot product of subtraction of a-th and b-th vector. c = (a-b)'*(a-b)------------------------------------------------------------------- */double sub_dot_prod( long a, long b ){   double c = 0;   long i;   for( i = 0; i < dim; i++ ) {      c += (*(dataA+(a*dim)+i) - *(dataB+(b*dim)+i))*           (*(dataA+(a*dim)+i) - *(dataB+(b*dim)+i));   }   return( c );}/* -------------------------------------------------------------------- Converts string kernel identifier to int.-------------------------------------------------------------------- */int kernel_id( const mxArray *prhs1 ){  int num, i, buf_len;  char *buf;  if( mxIsChar( prhs1 ) != 1) return( -1 );  buf_len  = (mxGetM(prhs1) * mxGetN(prhs1)) + 1;  buf = mxCalloc( buf_len, sizeof( char ));  mxGetString( prhs1, buf, buf_len );    num = sizeof( kernel_name )/sizeof( char * );  for( i = 0; i < num; i++ ) {    if( strcmp( buf, kernel_name[i] )==0 ) return( i );  }  return(-1);}/* -------------------------------------------------------------------- Computes kernel function for a-th and b-th. The base address for the 1st argument is dataA and for the 2nd argument is dataB.-------------------------------------------------------------------- */double kernel( long a, long b ){   double c = 0;   ker_cnt++;   switch( ker ) {      /* linear kernel */      case 0:         c = dot_prod( a, b );         break;      /* polynomial kernel */      case 1:         c = pow( (dot_prod( a, b) + arg1[1]), arg1[0] );         break;      /* radial basis functions kernel*/      case 2:         c = exp( -0.5*sub_dot_prod( a, b)/(arg1[0]*arg1[0]) );         break;      /* sigmoid */      case 3:              c = tanh( arg1[0]*dot_prod( a,b) + arg1[1] );         break;      default:         c = 0;   }   return( c );}