gnu1987/bison-1.21/warshall.c

/* Generate transitive closure of a matrix,
   Copyright (C) 1984, 1989 Free Software Foundation, Inc.

This file is part of Bison, the GNU Compiler Compiler.

Bison is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2, or (at your option)
any later version.

Bison is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with Bison; see the file COPYING.  If not, write to
the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.  */


#include <stdio.h>
#include "system.h"
#include "machine.h"


/* given n by n matrix of bits R, modify its contents
   to be the transive closure of what was given.  */

void
TC(R, n)
unsigned *R;
int n;
{
  register int rowsize;
  register unsigned mask;
  register unsigned *rowj;
  register unsigned *rp;
  register unsigned *rend;
  register unsigned *ccol;

  unsigned *relend;
  unsigned *cword;
  unsigned *rowi;

  rowsize = WORDSIZE(n) * sizeof(unsigned);
  relend = (unsigned *) ((char *) R + (n * rowsize));

  cword = R;
  mask = 1;
  rowi = R;
  while (rowi < relend)
    {
      ccol = cword;
      rowj = R;

      while (rowj < relend)
	{
	  if (*ccol & mask)
	    {
	      rp = rowi;
	      rend = (unsigned *) ((char *) rowj + rowsize);

	      while (rowj < rend)
		*rowj++ |= *rp++;
	    }
	  else
	    {
	      rowj = (unsigned *) ((char *) rowj + rowsize);
	    }

	  ccol = (unsigned *) ((char *) ccol + rowsize);
	}

      mask <<= 1;
      if (mask == 0)
	{
	  mask = 1;
	  cword++;
	}

      rowi = (unsigned *) ((char *) rowi + rowsize);
    }
}


/* Reflexive Transitive Closure.  Same as TC
   and then set all the bits on the diagonal of R.  */

void
RTC(R, n)
unsigned *R;
int n;
{
  register int rowsize;
  register unsigned mask;
  register unsigned *rp;
  register unsigned *relend;

  TC(R, n);

  rowsize = WORDSIZE(n) * sizeof(unsigned);
  relend = (unsigned *) ((char *) R + n*rowsize);

  mask = 1;
  rp = R;
  while (rp < relend)
    {
      *rp |= mask;

      mask <<= 1;
      if (mask == 0)
	{
	  mask = 1;
	  rp++;
	}

      rp = (unsigned *) ((char *) rp + rowsize);
    }
}