check_hmm_restriction.c

Go to the documentation of this file.

/*
 * Copyright (c) 1991-2006 Kawahara Lab., Kyoto University
 * Copyright (c) 2000-2005 Shikano Lab., Nara Institute of Science and Technology
 * Copyright (c) 2005-2006 Julius project team, Nagoya Institute of Technology, Nagoya Institute of Technology
 * All rights reserved
 */

#include <sent/stddefs.h>
#include <sent/htk_hmm.h>
#include <sent/htk_param.h>
#include <sent/hmm.h>

#define GOOD 0                  
#define FIXED 1                 
#define BAD 3                   

/* transition allowance matrix on normal version */
/* G=good,F=fixed,B=bad */
/*  |G|F|B */
/* -+-+-+- */
/* G|G|F|B */
/* F|F|F|B */
/* B|B|B|B */

/* transition probability is not loganized yet */

static int
trans_ok_p(HTK_HMM_Trans *t)
{
#ifdef MULTIPATH_VERSION
  int i;
  int tflag;
  int retflag = GOOD;

  /* no arc to initial state */
  tflag = GOOD;
  for (i=0;i<t->statenum;i++) {
    if (t->a[i][0] != (PROB)0.0) {
      tflag = BAD;
      break;
    }
  }
  if (tflag == BAD) {
    j_printerr("Error: transition to initial state not allowed\n");
    retflag = BAD;
  }
  /* no arc from final state */
  tflag = GOOD;
  for (i=0;i<t->statenum;i++) {
    if (t->a[t->statenum-1][i] != (PROB)0.0) {
      tflag = BAD;
      break;
    }
  }
  if (tflag == BAD) {
    j_printerr("Error: transition from final state not allowed\n");
    retflag = BAD;
  }
    
  return(retflag);
  
#else  /* ~MULTIPATH_VERSION */
  
  int i, j;
  int tflag = BAD;
  int retflag = BAD;
  PROB maxprob;
  int maxid = -1;
  
  /* allow only one arc from initial state */
  tflag = BAD;
  for (i=0;i<t->statenum;i++) {
    if (t->a[0][i] != (PROB)0.0) {
      if (tflag == BAD) {
        tflag = GOOD;
      } else {                  /* 2nd time */
        j_printerr("Warning: initial state has more than one arc\n");
        tflag = BAD;
        break;
      }
    }
  }
  if (tflag == BAD) {           /* unacceptable transition found */
    if (i >= t->statenum) {     /* no arc */
      j_printerr("Error: initial state has no arc\n");
    } else {
      /* modify the transition: gather them to an arc with best probability */
      maxprob = 0.0; maxid = -1;
      for (j=0;j<t->statenum;j++) {
        if (maxprob < t->a[0][j]) {
          maxprob = t->a[0][j];
          maxid = j;
        }
      }
      if (maxid == -1) {
        j_error("Error: trans_ok_p: no transition in a state?\n");
      }
      t->a[0][maxid] = 1.0;
      for (j=0;j<t->statenum;j++) {
        if (j == maxid) continue;
        t->a[0][j] = 0.0;
      }
      tflag = FIXED;
    }
  }

  retflag = tflag;
  
  /* allow only one arc to final state */
  tflag = BAD;
  for (i=0;i<t->statenum;i++) {
    if (t->a[i][t->statenum-1] != (PROB)0.0) {
      if (tflag == BAD) {
        tflag = GOOD;
      } else {                  /* 2nd time */
        j_printerr("Warning: more than one arc to end state\n");
        tflag = BAD;
        break;
      }
    }
  }
  if (tflag == BAD) {
    if (i >= t->statenum) {     /* no arc */
      j_printerr("Error: no arc to end state\n");
    } else {
      /* modify the transition: gather them to an arc with best probability */
      maxprob = (PROB)0.0;
      for (j=0;j<t->statenum;j++) {
        if (maxprob < t->a[j][t->statenum-1]) {
          maxprob = t->a[j][t->statenum-1];
          maxid = j;
        }
      }
      for (i=0;i<t->statenum;i++) {
        if (t->a[i][t->statenum-1] == (PROB)0.0) continue;
        if (i == maxid) continue;
        for (j=t->statenum-2;j>=0;j--) {
          if (t->a[i][j] != (PROB)0.0) {
            t->a[i][j] += t->a[i][t->statenum-1];
            t->a[i][t->statenum-1] = (PROB)0.0;
            break;
          }
        }
      }
      tflag = FIXED;
    }
  }
    
  return(retflag | tflag);

#endif /* MULTIPATH_VERSION */
}

boolean
check_hmm_limit(HTK_HMM_Data *dt)
{
  boolean return_flag = TRUE;
  int tflag;

  tflag = trans_ok_p(dt->tr);
  if (tflag == BAD) {
    return_flag = FALSE;
    j_printerr("Limit: HMM \"%s\" has unsupported arc.\n", dt->name);
    put_htk_trans(dt->tr);
  } else if (tflag == FIXED) {
    j_printerr("Warning: HMM \"%s\" has unsupported arc.\n", dt->name);
    j_printerr("SERIOUS WARNING: Transition arc has been modified as below\n");
    j_printerr("SERIOUS WARNING: This may cause unintended recognition result\n");
    put_htk_trans(dt->tr);
  }
#ifdef MULTIPATH_VERSION
  if (dt->tr->statenum < 3) {
    return_flag = FALSE;
    j_printerr("Limit: HMM \"%s\" has no output state (statenum=%d)\n", dt->name, dt->tr->statenum);
  }
#endif
  return(return_flag);
}

boolean
check_all_hmm_limit(HTK_HMM_INFO *hmminfo)
{
  HTK_HMM_Data *dt;
  boolean return_flag = TRUE;

  for (dt = hmminfo->start; dt; dt = dt->next) {
    if (check_hmm_limit(dt) == FALSE) {
      return_flag = FALSE;
    }
  }
  return(return_flag);
}


#ifdef MULTIPATH_VERSION

boolean
is_skippable_model(HTK_HMM_Data *d)
{
  if (d->tr->a[0][d->tr->statenum-1] != LOG_ZERO) {
    return TRUE;
  }
  return FALSE;
}
#endif

---