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KLD.cpp
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KLD.cpp
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#include "mex.h"
#include "math.h"
#include "matrix.h"
#include "string.h"
void KLD(double* prob1, double *prob2, mwSize dist_size, double* kld_value);
void mexFunction(int nlhs, mxArray *plhs[], int nrhs, const mxArray *prhs[])
{
double* prob1, *prob2;
mwSize dist_size;
prob1 = mxGetPr(prhs[0]);
prob2 = mxGetPr(prhs[1]);
dist_size = mxGetM(prhs[0]);
plhs[0] = mxCreateDoubleMatrix(1, 1, mxREAL);
double* kld_value = mxGetPr(plhs[0]);
//mxArray *binaryValueArray = mxCreateDoubleMatrix(binaryValueSize, 1, mxREAL);
KLD(prob1, prob2, dist_size, kld_value);
}
void KLD(double* prob1, double *prob2, mwSize dist_size, double* kld_value)
{
double h1 = 0;
for (int i = 0; i < dist_size; i++) {
bool changed = false;
if (prob2[i] == 0) {
prob2[i] = 1;
changed = true;
}
h1 += log2(prob2[i]) * prob1[i];
if (changed)
prob2[i] = 0;
}
double h2 = 0;
for (int i = 0; i < dist_size; i++) {
bool changed = false;
if (prob1[i] == 0) {
prob1[i] = 1;
changed = true;
}
h2 += log2(prob1[i]) * prob1[i];
if (changed)
prob1[i] = 0;
}
*kld_value = h2 - h1;
}
// matlab function
// prob2(prob2==0) = 1; % avoid log0 when computing entropy
// H1 = - sum(prob.*log2(prob2)) ;
//
// prob(prob==0) = 1;
// H2 = - sum(prob.*log2(prob));
// H = H1 - H2;