viterbi.c

HMM的演示源程序

#include <math.h>
#include "hmm.h"
#include "nrutil.h"
#define VITHUGE  100000000000.0

void Viterbi(HMM *phmm, int T, int *O, double **delta, int **psi, int *q, double *pprob)
{
	int 	i, j;
	int  	t;	

	int	maxvalind;
	double	maxval, val;

	for (i = 1; i <= phmm->N; i++) {
		delta[1][i] = phmm->pi[i] * (phmm->B[i][O[1]]);
		psi[1][i] = 0;
	}	

	for (t = 2; t <= T; t++) {
		for (j = 1; j <= phmm->N; j++) {
			maxval = 0.0;
			maxvalind = 1;	
			for (i = 1; i <= phmm->N; i++) {
				val = delta[t-1][i]*(phmm->A[i][j]);
				if (val > maxval) {
					maxval = val;	
					maxvalind = i;	
				}
			}
			
			delta[t][j] = maxval*(phmm->B[j][O[t]]);
			psi[t][j] = maxvalind; 
		}
	}

	*pprob = 0.0;
	q[T] = 1;
	for (i = 1; i <= phmm->N; i++) {
                if (delta[T][i] > *pprob) {
			*pprob = delta[T][i];	
			q[T] = i;
		}
	}

	for (t = T - 1; t >= 1; t--)
		q[t] = psi[t+1][q[t+1]];
}

void ViterbiLog(HMM *phmm, int T, int *O, double **delta, int **psi, int *q, double *pprob)
{
        int     i, j;
        int     t;   

        int     maxvalind;
        double  maxval, val;
	double  **biot;

	for (i = 1; i <= phmm->N; i++) 
		phmm->pi[i] = log(phmm->pi[i]);
	for (i = 1; i <= phmm->N; i++) 
		for (j = 1; j <= phmm->N; j++) {
			phmm->A[i][j] = log(phmm->A[i][j]);
		}

	biot = dmatrix(1, phmm->N, 1, T);
	for (i = 1; i <= phmm->N; i++) 
		for (t = 1; t <= T; t++) {
			biot[i][t] = log(phmm->B[i][O[t]]);
		}

        for (i = 1; i <= phmm->N; i++) {
                delta[1][i] = phmm->pi[i] + biot[i][1];
                psi[1][i] = 0;
        }

        for (t = 2; t <= T; t++) {
                for (j = 1; j <= phmm->N; j++) {
                        maxval = -VITHUGE;
                        maxvalind = 1;
                        for (i = 1; i <= phmm->N; i++) {
                                val = delta[t-1][i] + (phmm->A[i][j]);
                                if (val > maxval) {
                                        maxval = val;
                                        maxvalind = i;
                                }
                        }

                        delta[t][j] = maxval + biot[j][t]; 
                        psi[t][j] = maxvalind;
                }
        }

        *pprob = -VITHUGE;
        q[T] = 1;
        for (i = 1; i <= phmm->N; i++) {
                if (delta[T][i] > *pprob) {
                        *pprob = delta[T][i];
                        q[T] = i;
                }
        }

	for (t = T - 1; t >= 1; t--)
		q[t] = psi[t+1][q[t+1]];
}