decode.c

ldpc的11个程序 encode decode extract make-gen make-ldpc make-pchk print-gen print-pchk rand-src transm

/* DECODE.C - Decode blocks of received data. */

/* Copyright (c) 2000, 2001 by Radford M. Neal 
 *
 * Permission is granted for anyone to copy, use, or modify this program 
 * for purposes of research or education, provided this copyright notice 
 * is retained, and note is made of any changes that have been made. 
 *
 * This program is distributed without any warranty, express or implied.
 * As this program was written for research purposes only, it has not been
 * tested to the degree that would be advisable in any important application.
 * All use of this program is entirely at the user's own risk.
 */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <math.h>

#include "rand.h"
#include "alloc.h"
#include "blockio.h"
#include "open.h"
#include "mod2sparse.h"
#include "mod2dense.h"
#include "mod2convert.h"
#include "channel.h"
#include "rcode.h"
#include "check.h"
#include "dec.h"


void usage(void);


/* MAIN PROGRAM. */

int main( int argc, char **argv)
{
  char *pchk_file, *rfile, *dfile, *pfile;
  char **meth;
  FILE *rf, *df, *pf;

  char *dblk, *pchk;
  double *lratio;
  double *bitpr;

  double *awn_data;		/* Places to store channel data */
  int *bsc_data;

  unsigned iters;		/* Unsigned because can be huge for enum */
  double tot_iter;		/* Double because can be huge for enum */
  double chngd, tot_changed;	/* Double because can be fraction if lratio==1*/

  int tot_valid;
  char junk;
  int valid;

  int i, j, k;

  /* Look at arguments up to the decoding method specification. */

  table = 0;
  if (argc>1 && strcmp(argv[1],"-t")==0)
  { 
	table = 1;
    argc -= 1;
    argv += 1;
  }
  if (argc>1 && strcmp(argv[1],"-T")==0)
  { 
	table = 2;
    argc -= 1;
    argv += 1;
  }

  if (!(pchk_file = argv[1]) || !(rfile = argv[2]) || !(dfile = argv[3]))
  { 
	  usage();
  }

  if (argv[4]==0 || argv[5]==0) usage();

  k = channel_parse(argv+4,argc-4);//bp-file bsc 0.1 prprp -100;
  if (k<=0)
  {
	pfile = argv[4];
    k = channel_parse(argv+5,argc-5);
    if (k<=0) usage();
    meth = argv+5+k;
  }
  else
  { 
	pfile = 0;
    meth = argv+4+k;
  }

  /* Look at the specification of the decoding method, which starts at meth and
     continues to the end of the command line (marked by a zero pointer). */

  if (!meth[0]) usage();

  if (strcmp(meth[0],"prprp")==0)
  { 
	dec_method = Prprp;
    if (!meth[1] || sscanf(meth[1],"%d%c",&max_iter,&junk)!=1 || meth[2]) 
    { 
		usage();
    }
  }
  else if (strcmp(meth[0],"enum-block")==0)
  { 
	dec_method = Enum_block;
    if (!(gen_file = meth[1]) || meth[2]) usage();
  }
  else if (strcmp(meth[0],"enum-bit")==0)
  { 
	dec_method = Enum_bit;
    if (!(gen_file = meth[1]) || meth[2]) usage();
  }
  else 
  { 
	  usage();
  }

  /* Check that we aren't overusing standard input or output. */

  if ((strcmp(pchk_file,"-")==0) + (strcmp(rfile,"-")==0) > 1)
  { 
	fprintf(stderr,"Can't read more than one stream from standard input\n");
    exit(1);
  }
  if ((table>0) + (strcmp(dfile,"-")==0) + (pfile!=0 && strcmp(pfile,"-")==0) > 1)
  { 
	fprintf(stderr,"Can't send more than one stream to standard output\n");
    exit(1);
  }

  /* Read parity check file. */
  read_pchk(pchk_file);

//  struct mod2entry *e;
 // ee = mod2sparse_first_in_col(H,3);

  if (N<=M)
  { 
	fprintf(stderr, "Number of bits (%d) should be greater than number of checks (%d)\n",N,M);
    exit(1);
  }

  /* Open file of received data. */
  rf = open_file_std(rfile,"r");
  if (rf==NULL)
  { 
	fprintf(stderr,"Can't open file of received data: %s\n",rfile);
    exit(1);
  }

  /* Create file for decoded data. */

  df = open_file_std(dfile,"w");
  if (df==NULL)
  { 
	fprintf(stderr,"Can't create file for decoded data: %s\n",dfile);
    exit(1);
  }

  /* Create file for bit probabilities, if specified. */

  if (pfile)
  { 
	pf = open_file_std(pfile,"w");
    if (pf==NULL)
    { 
	  fprintf(stderr,"Can't create file for bit probabilities: %s\n",pfile);
      exit(1);
    }
  }

  /* Allocate space for data from channel. */
  switch (channel)
  { 
    case BSC:
    { 
	  bsc_data = chk_alloc (N, sizeof *bsc_data);
      break;
    }
    case AWGN: case AWLN:
    { 
	  awn_data = chk_alloc (N, sizeof *awn_data);
      break;
    }
    default:
    { 
	  abort();
    }
  }

  /* Allocate other space. */
  dblk   = chk_alloc (N, sizeof *dblk);
  lratio = chk_alloc (N, sizeof *lratio);
  pchk   = chk_alloc (M, sizeof *pchk);
  bitpr  = chk_alloc (N, sizeof *bitpr);

  /* Print header for summary table. */

  if (table==1)
  { 
	  printf("  block iterations valid  changed\n");
  }

  /* Do the setup for the decoding method. */
  switch (dec_method)
  { 
    case Prprp: 
    { 
	  prprp_decode_setup();
      break;
    }
  }

  /* Read received blocks, decode, and write decoded blocks. */

  tot_iter = 0;
  tot_valid = 0;
  tot_changed = 0;

  for (block_no = 0; ; block_no++)
  { 
		/* Read block from received file, exit if endo-f-file encountered. */
	    //下面的for循环，读一个块出来，从1到N，长度为N;
		for (i = 0; i<N; i++)
		{ 
			  int c;
			  switch (channel)
			  { 
					case AWGN: case AWLN:
					{
					  c = fscanf(rf,"%lf",&awn_data[i]); 
					  break;
					}
			  }
			  if (c==EOF) 				  
			  { 
				int iyy=8888;
				if (i>0)
				{ 
					fprintf(stderr, "Warning: Short block (%d long) at end of received file ignored\n",i);
				}
				goto done;
			  }
			  if (c<1 || channel==BSC && bsc_data[i]!=0 && bsc_data[i]!=1)
			  { 
				fprintf(stderr,"File of received data is garbled\n");
				exit(1);
			  }
		}//for (i = 0; i<N; i++);

		/* Find likelihood ratio for each bit. */

		//下面这个switch解决了lratio的数值；一个block,从1到N;
		switch (channel)
		{ 
			  case AWGN:
			  { 
				for (i = 0; i<N; i++)
				{ 
					lratio[i] = exp(2*awn_data[i]/(std_dev*std_dev));
				}
				break;
			  }
		}

		/* Try to decode using the specified method. */
		switch (dec_method)
		{ 
			  case Prprp:
			  { 
				iters = prprp_decode (H, lratio, dblk, pchk, bitpr);//lratio=1/9 when 0;or lratio=9when 1;
				//上面的函数后3个参数好像都是输出参量啊，这3个参数在这儿给的都是地址,即指针形式，没有内容；
				break;
			  }
		}

		/* See if it worked, and how many bits were changed. */
		valid = check(H,dblk,pchk)==0;
		chngd = changed(lratio,dblk,N);
	//	printf("%s",dblk);
	//	printf("%s",pchk);
	//	printf("%s",bitpr);

		tot_iter += iters;
		tot_valid += valid;
		tot_changed += chngd;

		/* Print summary table entry. */
		if (table==1)
		{ 
		  printf ("%7d %10f  %d  %8.1f\n", block_no, (double)iters, valid, (double)chngd);///和上面的table==1互相对应；
			/* iters is printed as a double to avoid problems if it's >= 2^31 */
		  fflush(stdout);
		}

		/* Write decoded block. */
		blockio_write(df,dblk,N);

		/* Write bit probabilities, if asked to. */
		if (pfile)
		{ 
		  for (j = 0; j<N; j++)
		  { 
			  fprintf(pf," %.5f",bitpr[j]);
		  }
		  fprintf(pf,"\n");
		}
  }////for (block_no = 0; ; block_no++)

	  /* Finish up. */
   done: 
	  fprintf(stderr, "Decoded %d blocks, %d valid.  Average %.1f iterations, %.0f%% bit changes\n", block_no, tot_valid, (double)tot_iter/block_no, 100.0*(double)tot_changed/(N*block_no));
	  if (ferror(df) || fclose(df)!=0)
	  { 
		fprintf(stderr,"Error writing decoded blocks to %s\n",dfile);
		exit(1);
	  }

	  if (pfile)
	  { 
		if (ferror(pf) || fclose(pf)!=0)
		{ 
		  fprintf(stderr,"Error writing bit probabilities to %s\n",dfile);
		  exit(1);
		}
	  }
   exit(0);
}//main( int argc, char **argv)
/* PRINT USAGE MESSAGE AND EXIT. */
//}

void usage(void)
{ 
  fprintf(stderr,"Usage:\n");
  fprintf(stderr,"  decode [ -t ] pchk-file received-file decoded-file [ bp-file ] channel method\n");
  channel_usage();
  fprintf(stderr,"Method:  enum-block gen-file | enum-bit gen-file | prprp [-]max-iterations\n");
  exit(1);
}