rm.h

快速傅立叶变换程序代码,学信号的同学,可要注意了

typedef struct {
  int N ; /* The length of the code is its chief defining property
	     from which we deduce K,M, assuming it is a Hamming or RM code */
  int M ;
  int K ;
  int I ; /* number of conceivable states 2^M-1 */
  int *pint ; /* the parity matrix pint[1]..pint[N] expressed using integers */
  /* for H systematic, pint[1]...[15] = 3,5,6,7,9,10,11,12,13,14,15,1,2,4,8 */
  /* for H, pint[1]...[15] = 1,2,3,..13,14,15 */
  /* for RM, pint[1]...[16] = 16+0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15  */ 
  unsigned char **p ; /* this is a place to write the bits explicitly 
			 if required */
  int **v ; /* whether a state v[l][i] is a valid part of the trellis,
	       and if so, which transitions it can make forward and backward
	       (stored as f0 + 8f1 + 64b0 + 8^3 b1 ) */
  int **nexti ; /* nexti[l][i] points to the next i in this column which is 
		   a valid trellis state; or zero when done */

  double **q ; /* incoming likelihoods for each bit q[l][0/1] */
  double **f ;
  double **b ; /* forward and backward probs f[l][i] */
  double **r ; /* outgoing likelihoods */
  double **po ; /* outgoing posteriors (added Tue 24/4/01) */
  /* Wed 25/4/01 : */
  /* in the KIKUCHI approach, we view the trellis state as a function of the
     imposed MARGINALS, which are the posterior probabilities */
  /* we must adjust the q's so as to match these */
  double *lq   ; /* lagrange multipliers that define the incoming likelihoods */
  double *pob  ; /* required values for the posterior probabilities  */
  double *lpob ; /* required values for the logits  */
  double *lpo  ; /* logit of outgoing posteriors    */

  unsigned char *xo ; /* a tentative codeword for testing against the trellis */

  int computeS ; /* compute the entropy when running forward backward */
                 /* Mon 23/4/01 */
  double S ;
  double ML ; /* marginal likelihood, also computed when we find the entropy */
  double **Ef ;
  double **Eb ; /* forward and backward energies Ef[l][i] */
  double **Sc ; /* entropy of rest of trellis conditional on being in this state */
  double **Ec ;
  double **Scbit ;
  double **Sf ;
  double **Sb ;
  double *Srest ; /* entropy of rest of states */
  double *dSdl ; /* derviative of entropy wrt lagrange multipliers */
  double *dSdpo ; /* derviative of entropy wrt "posterior" */
  double S1 ; /* special treatment for the very first bit: we note the entropy
		 associated with its left-right transition for debugging purposes */

  double fudge[10] ; /* used in the match routine */
  /* idea: alternate between two reasonable values, rather than faffing about
     with adaptation! */
  int fudgeperiod ;
  int T ;/* number of match iterations */
  int verbose ;
  
} linear_trellis ;

void zero_linear_trellis ( linear_trellis *h ) ;
void free_linear_trellis ( linear_trellis *h ) ;
void make_linear_trellis ( linear_trellis *h , int NH , int type , int verbose ) ;
void zero_energy_trellis ( linear_trellis *h ) ;
void free_energy_trellis ( linear_trellis *h ) ;
void make_energy_trellis ( linear_trellis *h ) ; 
void lt_zero_r ( linear_trellis *h ) ;
void lt_fb ( linear_trellis *h ) ;
void lt_match ( linear_trellis *h ) ;
/* void lt_fbS ( linear_trellis *h ) ; Mon 23/4/01 */
void lt_gnu ( linear_trellis *h, const char path[] ) ;
int lt_syndrome ( linear_trellis *h ) ;
double H2 ( double x ) ;