vitshort.c

数字通信第四版原书的例程

/* ===========================================================================
 *  function out = vitshort(fst_in, snd_in, n_sta, mima)
 *   VITSHORT makes two steps of transfering expense into one step expense.
 *   OUT = VITSHORT(FST_IN SCD_IN, N_STA, MIMA)
 *   FST_IN, step one
 *   SND_IN, step two
 *   N_STA,  number of state
 *   MIMA,   ==1 to find the minimum, == 0 to find the maximum
 *   OUT, FST_IN, and SND_IN are size 2^n_sta row vectors which recorded the 
 *      data of [d00, d10, d20, ..., dn0, d01, d11, d21,..., dn1, ...., d0n, 
 *                                          d1n, d2n, ...., dnn]
 *   where dij means the cost of transfering state i to state j.
 *   dij = NaN means that there is no transfering between the two states.
 *
 *   Used by viterbi.
 * ===========================================================================
 *   Jun Wu, Jan 2nd, 1996
 *   Revised Wes Wang Jan. 9, 1996
 *
 *   Copyright (c) 1996 The MathWorks, Inc.
 *   All Rights Reserved
 *   $Revision: 1.1 $  $Date: 1996/04/01 18:15:03 $
 * =========================================================================
 */
#include <math.h>
#include "mex.h"
void mexFunction(int nlhs, Matrix *plhs[], int nrhs, Matrix *prhs[])
{
    int     i, j, k, nsta, pow_sta, aft_indx, len_indx, len, indx;
    int     *wei_indx, *sub_indx;
    double  max, min;
    double  *wei_mat_fst, *wei_sum;
    double  wei_mat_snd;    
    double  *FstIn, *SndIn, *NSta, *MiMa, *Out;
    double  NaN  = mexGetNaN();
    
    FstIn = mxGetPr(prhs[0]);
    SndIn = mxGetPr(prhs[1]);
    NSta =  mxGetPr(prhs[2]);
    MiMa =  mxGetPr(prhs[3]);
    
    /*pow_sta = length(fst_in);*/
    pow_sta = mxGetM(prhs[0])*mxGetN(prhs[0]);

    Out = mxGetPr(plhs[0] = mxCreateFull(1,pow_sta,0));
    nsta = (int)NSta[0];
    wei_mat_fst = (double *)mxCalloc(nsta, sizeof(double));
    wei_sum     = (double *)mxCalloc(nsta, sizeof(double));
    wei_indx    = (int *)mxCalloc(nsta, sizeof(int));
    sub_indx    = (int *)mxCalloc(nsta, sizeof(int));

    /*for i = 1 : n_sta
     *    aft_indx = i * n_sta - n_sta;
     */
    for(i=1; i <= nsta; i++){
        aft_indx = i * nsta - nsta;
        /* for j = 1 : n_sta
         *   wei_mat = [fst_in(j : n_sta : pow_sta);...
         *   snd_in(aft_indx+1 : aft_indx + n_sta)];
         *   wei_sum = sum(wei_mat);
         *   wei_indx = find(~isnan(wei_sum));
         */
        for(j=1; j <= nsta; j++){
            for(k=0; k < nsta; k++)
                wei_mat_fst[k] =FstIn[k * nsta + j - 1];
       	    len_indx = 0;
            for(k=0; k < nsta; k++){                
                wei_mat_snd = SndIn[aft_indx + k];
                if (mexIsNaN(wei_mat_fst[k]) || mexIsNaN(wei_mat_snd)) {
                    wei_sum[k] = NaN;
                } else {
            	    wei_sum[k] = wei_mat_fst[k] + wei_mat_snd;
        	        wei_indx[len_indx] = k;
        	        len_indx++;
                }
        	}

            /* if mima
             *    sub_indx = find(wei_sum == max(sum(wei_mat(:, wei_indx))));
             *    if length(sub_indx) > 1
             *        sub_indx = find(wei_mat(1,:) == max(wei_mat(1, sub_indx)));
             *    end;
             * else
             *    sub_indx = find(wei_sum == min(sum(wei_mat(:, wei_indx))));
             *    if length(sub_indx) > 1
             *        sub_indx = find(wei_mat(1,:) == min(wei_mat(1, sub_indx)));
             *    end;
             * end;
             */
            if (len_indx > 0) {
    			len = 0;
                if(MiMa[0] != 0 ){
                    max = wei_sum[wei_indx[0]];
                    sub_indx[0] = wei_indx[0];                    
                    k = 1;
                    while (k < len_indx) {
                        if ( max < wei_sum[wei_indx[k]] ) {
                            max = wei_sum[wei_indx[k]];
                            sub_indx[0] = wei_indx[k];
                        }
                        k++;
    				}
                    for(k=0; k < len_indx; k++){
                        if (wei_sum[wei_indx[k]] == max ){
                            sub_indx[len] = wei_indx[k];
                            len++;
                        }
                    }
                    indx = sub_indx[0];                        
                    if (len > 1){
                        max = wei_mat_fst[sub_indx[0]];
                        k = 1;
                        while(k < len){
                            if( max < wei_mat_fst[sub_indx[k]] ) {
                                max = wei_mat_fst[sub_indx[k]];
                                indx = sub_indx[k];
                            }
                            k++;
                        }
                    }
		    	} else {
                    min = wei_sum[wei_indx[0]];
                    sub_indx[0] = wei_indx[0];
                    k = 1;
                    while (k < len_indx){
                        if ( min > wei_sum[wei_indx[k]] ) {
                            min = wei_sum[wei_indx[k]];
                            sub_indx[0] = wei_indx[k];                            
                        }
                        k++;
    				}
                    for(k=0; k < len_indx; k++){
                        if (wei_sum[wei_indx[k]] == min ){
                            sub_indx[len] = wei_indx[k];
                            len++;
                        }
                    }
                    indx = sub_indx[0];
                    if ( len > 1 ){
                        min = wei_mat_fst[sub_indx[0]];
                        k = 1;
                         while (k < len){
                            if( min > wei_mat_fst[sub_indx[k]] ) {
                                min = wei_mat_fst[sub_indx[k]];
                                indx = sub_indx[k];
                            }
                            k++;
                        }
                    } else {
                        indx = sub_indx[0];
                    }
                }
                /*        if ~isempty(sub_indx)
                 *            out(aft_indx + j) = wei_sum(sub_indx(1));
                 *        else
                 *            out(aft_indx + j) = NaN;
                 *        end;
                 *    end;
                 *end;
                 */
                Out[aft_indx + j - 1] = wei_sum[indx];    
            } else {
                Out[aft_indx + j - 1] = NaN;
			}
		}
	}
	return;
}