source: git/src/netartic.c @ 736f7df

/* netartic.c
 * Split up network at articulation points
 * Copyright (C) 1993-2003,2005,2012,2014 Olly Betts
 *
 * This program 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 of the License, or
 * (at your option) any later version.
 *
 * This program 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 this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 */

#if 0
# define DEBUG_INVALID 1
# define DEBUG_ARTIC
#endif

#ifdef HAVE_CONFIG_H
# include <config.h>
#endif

#include "debug.h"
#include "cavern.h"
#include "filename.h"
#include "listpos.h"
#include "message.h"
#include "netartic.h"
#include "netbits.h"
#include "matrix.h"
#include "out.h"

/* We want to split station list into a list of components, each of which
 * consists of a list of "articulations" - the first has all the fixed points
 * in that component, and the others attach sequentially to produce the whole
 * component
 */

typedef struct articulation {
   struct articulation *next;
   node *stnlist;
} articulation;

typedef struct component {
   struct component *next;
   articulation *artic;
} component;

static component *component_list;

static articulation *articulation_list;

static node *artlist;

static node *fixedlist;

static long colour;

/* The goto iter/uniter avoids using recursion which could lead to stack
 * overflow.  Instead we use 5 bytes of memory per iteration in malloc-ed
 * blocks which will probably use an awful lot less memory on most platforms.
 */

/* This is the number of station in stnlist which is a ceiling on how
 * deep visit will recurse */
static unsigned long cMaxVisits;

static unsigned char *dirn_stack = NULL;
static long *min_stack = NULL;

static unsigned long
visit(node *stn, int back)
{
   long min_colour;
   int i;
   unsigned long tos = 0;
   SVX_ASSERT(dirn_stack && min_stack);
#ifdef DEBUG_ARTIC
   printf("visit(%p, %d) called\n", stn, back);
#endif

iter:
   min_colour = stn->colour = ++colour;
#ifdef DEBUG_ARTIC
   printf("visit: stn [%p] ", stn);
   print_prefix(stn->name);
   printf(" set to colour %ld -> min\n", colour);
#endif
   for (i = 0; i <= 2 && stn->leg[i]; i++) {
      if (i != back) {
         node *to = stn->leg[i]->l.to;
         long col = to->colour;
         if (col == 0) {
            SVX_ASSERT(tos < cMaxVisits);
            dirn_stack[tos] = back;
            min_stack[tos] = min_colour;
            tos++;
            back = reverse_leg_dirn(stn->leg[i]);
            stn = to;
            goto iter;
uniter:
            SVX_ASSERT(tos > 0);
            --tos;
            i = reverse_leg_dirn(stn->leg[back]);
            to = stn;
            stn = to->leg[back]->l.to;
            back = dirn_stack[tos];
            if (min_stack[tos] < min_colour) min_colour = min_stack[tos];

#ifdef DEBUG_ARTIC
            printf("unwind: stn [%p] ", stn);
            print_prefix(stn->name);
            printf(" colour %d, min %d, station after %d\n", stn->colour,
                   min_colour, to->colour);
            printf("Putting stn ");
            print_prefix(to->name);
            printf(" on artlist\n");
#endif
            remove_stn_from_list(&stnlist, to);
            add_stn_to_list(&artlist, to);

            if (to->colour <= min_colour) {
               articulation *art;

               min_colour = to->colour;

               /* FIXME: note down leg (<-), remove and replace:
                *                 /\   /        /\
                * [fixed point(s)]  *-*  -> [..]  )
                *                 \/   \        \/
                *                 stn to
                */
               /* flag leg as an articulation for loop error reporting */
               to->leg[dirn_stack[tos]]->l.reverse |= FLAG_ARTICULATION;
               stn->leg[i]->l.reverse |= FLAG_ARTICULATION;

               /* start new articulation */
               art = osnew(articulation);
               art->stnlist = artlist;
               art->next = articulation_list;
               articulation_list = art;
               artlist = NULL;

#ifdef DEBUG_ARTIC
               printf("Articulate *-");
               print_prefix(stn->name);
               printf("-");
               print_prefix(to->name);
               printf("-...\n");
#endif
            }
         } else {
            /* back edge case */
            if (col < 0) {
               /* we've found a fixed point */
               col = -col;
               to->colour = col;
#if 0
               /* Removing this solves Graham Mullan's problem and makes more
                * sense since it means we'll recheck this point for further
                * legs. */
#ifdef DEBUG_ARTIC
               printf("Putting FOUND FIXED stn ");
               print_prefix(to->name);
               printf(" on artlist\n");
#endif
               remove_stn_from_list(&fixedlist, to);
               add_stn_to_list(&artlist, to);
#endif
            }

            if (col < min_colour) min_colour = col;
         }
      }
   }

   SVX_ASSERT(!stn->leg[0] || stn->leg[0]->l.to->colour > 0);
   SVX_ASSERT(!stn->leg[1] || stn->leg[1]->l.to->colour > 0);
   SVX_ASSERT(!stn->leg[2] || stn->leg[2]->l.to->colour > 0);

   if (tos > 0) goto uniter;

#ifdef DEBUG_ARTIC
   printf("Putting stn ");
   print_prefix(stn->name);
   printf(" on artlist\n");
#endif
   remove_stn_from_list(&stnlist, stn);
   add_stn_to_list(&artlist, stn);
   return min_colour;
}

extern void
articulate(void)
{
   node *stn, *stnStart;
   int i;
   long cFixed;

   component_list = NULL;
   articulation_list = NULL;
   artlist = NULL;
   fixedlist = NULL;

   /* find articulation points and components */
   colour = 0;
   stnStart = NULL;
   cMaxVisits = 0;
   FOR_EACH_STN(stn, stnlist) {
      if (fixed(stn)) {
         remove_stn_from_list(&stnlist, stn);
         add_stn_to_list(&fixedlist, stn);
         colour++;
         stn->colour = -colour;
#ifdef DEBUG_ARTIC
         printf("Putting stn ");
         print_prefix(stn->name);
         printf(" on fixedlist\n");
#endif
      } else {
         cMaxVisits++;
         stn->colour = 0;
      }
   }
   dirn_stack = osmalloc(cMaxVisits);
   min_stack = osmalloc(cMaxVisits * sizeof(long));

   /* fixedlist can be NULL here if we've had a *solve followed by survey
    * which is all hanging. */
   cFixed = colour;
   while (fixedlist) {
      int c;
      stnStart = fixedlist;
      stn = stnStart;

      /* see if this is a fresh component - it may not be, we may be
       * processing the other way from a fixed point cut-line */
      if (stn->colour < 0) {
#ifdef DEBUG_ARTIC
         printf("new component\n");
#endif
         stn->colour = -stn->colour; /* fixed points are negative until we colour from them */
         cComponents++;

         /* FIXME: logic to count components isn't the same as the logic
          * to start a new one - we should start a new one for a fixed point
          * cut-line (see below) */
         if (artlist) {
             component *comp;
             articulation *art;

             art = osnew(articulation);
             art->stnlist = artlist;
             art->next = articulation_list;
             articulation_list = art;
             artlist = NULL;

             comp = osnew(component);
             comp->next = component_list;
             comp->artic = articulation_list;
             component_list = comp;
             articulation_list = NULL;
         }

#ifdef DEBUG_ARTIC
         print_prefix(stn->name);
         printf(" [%p] is root of component %ld\n", stn, cComponents);
         printf(" and colour = %d/%d\n", stn->colour, cFixed);
#endif
      }

      c = 0;
      for (i = 0; i <= 2 && stn->leg[i]; i++) {
         node *stn2 = stn->leg[i]->l.to;
         if (stn2->colour < 0) {
            stn2->colour = -stn2->colour;
         } else if (stn2->colour == 0) {
            /* Special case to check if start station is an articulation point
             * which it is iff we have to colour from it in more than one dirn
             *
             * We're looking for articulation legs - these are those where
             * colouring from here doesn't reach a fixed point (including
             * stn - the fixed point we've started from)
             *
             * FIXME: this is a "fixed point cut-line" case where we could
             * start a new component.
             */
            long col = visit(stn2, reverse_leg_dirn(stn->leg[i]));
#ifdef DEBUG_ARTIC
            print_prefix(stn->name);
            printf(" -> ");
            print_prefix(stn2->name);
            printf(" col %d cFixed %d\n", col, cFixed);
#endif
            if (col > cFixed) {
                /* start new articulation - FIXME - overeager */
                articulation *art = osnew(articulation);
                art->stnlist = artlist;
                art->next = articulation_list;
                articulation_list = art;
                artlist = NULL;
                c |= 1 << i;
            }
         }
      }

      switch (c) {
       /* had to colour in 2 or 3 directions from start point */
       case 3: case 5: case 6: case 7:
#ifdef DEBUG_ARTIC
         print_prefix(stn->name);
         printf(" is a special case start articulation point [%d]\n", c);
#endif
         for (i = 0; i <= 2 && stn->leg[i]; i++) {
            if (TSTBIT(c, i)) {
               /* flag leg as an articulation for loop error reporting */
               stn->leg[i]->l.reverse |= FLAG_ARTICULATION;
#ifdef DEBUG_ARTIC
               print_prefix(stn->leg[i]->l.to->name);
               putnl();
#endif
               reverse_leg(stn->leg[i])->l.reverse |= FLAG_ARTICULATION;
            }
         }
      }

#ifdef DEBUG_ARTIC
      printf("Putting FIXED stn ");
      print_prefix(stn->name);
      printf(" on artlist\n");
#endif
      remove_stn_from_list(&fixedlist, stn);
      add_stn_to_list(&artlist, stn);

      if (stnStart->colour == 1) {
#ifdef DEBUG_ARTIC
         printf("%ld components\n",cComponents);
#endif
         break;
      }
   }

   osfree(dirn_stack);
   dirn_stack = NULL;
   osfree(min_stack);
   min_stack = NULL;

   if (artlist) {
      articulation *art = osnew(articulation);
      art->stnlist = artlist;
      art->next = articulation_list;
      articulation_list = art;
      artlist = NULL;
   }
   if (articulation_list) {
      component *comp = osnew(component);
      comp->next = component_list;
      comp->artic = articulation_list;
      component_list = comp;
      articulation_list = NULL;
   }

   if (stnlist) {
      /* Any stations still in stnlist are unfixed, which is means we have
       * one or more hanging surveys.
       *
       * The cause of the problem is pretty likely to be a typo, so run the
       * checks which report errors and warnings about issues which such a
       * typo is likely to result in.
       */
      check_node_stats();

      /* Actually this error is fatal, but we want to list the survey
       * stations which aren't connected, so we report it as an error
       * and die after listing them...
       */
      bool fNotAttached = fFalse;
      error(/*Survey not all connected to fixed stations*/45);
      FOR_EACH_STN(stn, stnlist) {
         /* Anonymous stations must be at the end of a trailing traverse (since
          * the same anonymous station can't be referred to more than once),
          * and trailing traverses have been removed at this point.
          */
         SVX_ASSERT(!TSTBIT(stn->name->sflags, SFLAGS_ANON));
         if (stn->name->ident) {
            if (!fNotAttached) {
               fNotAttached = fTrue;
               /* TRANSLATORS: Here "station" is a survey station, not a train
                * station. */
               puts(msg(/*The following survey stations are not attached to a fixed point:*/71));
            }
            puts(sprint_prefix(stn->name));
         }
      }
      exit(EXIT_FAILURE);
   }

   {
      component *comp;

#ifdef DEBUG_ARTIC
      printf("\nDump of %d components:\n", cComponents);
#endif
      for (comp = component_list; comp; comp = comp->next) {
         node *list = NULL, *listend = NULL;
         articulation *art;
#ifdef DEBUG_ARTIC
         printf("Component:\n");
#endif
         SVX_ASSERT(comp->artic);
         for (art = comp->artic; art; art = art->next) {
#ifdef DEBUG_ARTIC
            printf("  Articulation (%p):\n", art->stnlist);
#endif
            SVX_ASSERT(art->stnlist);
            if (listend) {
               listend->next = art->stnlist;
               art->stnlist->prev = listend;
            } else {
               list = art->stnlist;
            }

            FOR_EACH_STN(stn, art->stnlist) {
#ifdef DEBUG_ARTIC
               printf("    %d %p (", stn->colour, stn);
               print_prefix(stn->name);
               printf(")\n");
#endif
               listend = stn;
            }
         }
#ifdef DEBUG_ARTIC
         putnl();
         FOR_EACH_STN(stn, list) {
            printf("MX: %c %p (", fixed(stn)?'*':' ', stn);
            print_prefix(stn->name);
            printf(")\n");
         }
#endif
         solve_matrix(list);
#ifdef DEBUG_ARTIC
         putnl();
         FOR_EACH_STN(stn, list) {
            printf("%c %p (", fixed(stn)?'*':' ', stn);
            print_prefix(stn->name);
            printf(")\n");
         }
#endif
         listend->next = stnlist;
         if (stnlist) stnlist->prev = listend;
         stnlist = list;
      }
#ifdef DEBUG_ARTIC
      printf("done articulating\n");
#endif
   }

#ifdef DEBUG_ARTIC
   /* test articulation */
   FOR_EACH_STN(stn, stnlist) {
      int d;
      int f;
      if (stn->name->ident && TSTBIT(stn->name->sflags, SFLAGS_FIXED)) {
         stn->colour = 1;
      } else {
         stn->colour = 0;
      }
      f = 0;
      for (d = 0; d < 3; d++) {
         if (stn->leg[d]) {
            if (f) {
               printf("awooga - gap in legs\n");
            }
            if (stn->leg[d]->l.reverse & FLAG_ARTICULATION) {
               if (!(reverse_leg(stn->leg[d])->l.reverse & FLAG_ARTICULATION)) {
                  printf("awooga - bad articulation (one way art)\n");
               }
            } else {
               if (reverse_leg(stn->leg[d])->l.reverse & FLAG_ARTICULATION) {
                  printf("awooga - bad articulation (one way art)\n");
               }
            }
         } else {
            f = 1;
         }
      }
   }

   colour = 2;

   while (1) {
      int c;
      int f;
      do {
         c = 0;
         FOR_EACH_STN(stn, stnlist) {
            int d;
            f = 0;
            for (d = 0; d < 3; d++) {
               if (stn->leg[d]) {
                  node *stn2 = stn->leg[d]->l.to;
                  if (f) {
                     printf("awooga - gap in legs\n");
                  }
                  if (stn2->colour) {
                     if (!(stn->leg[d]->l.reverse & FLAG_ARTICULATION)) {
                        if (stn->colour == 0) {
                           stn->colour = stn2->colour;
                           c++;
                        }
                     }
                  }
               } else {
                  f = 1;
               }
            }
         }
      } while (c);

      /* colour bits */
      FOR_EACH_STN(stn, stnlist) {
         if (stn->colour == 0) break;
      }
      if (!stn) break; /* all coloured */

      stn->colour = colour++;
   }

   FOR_EACH_STN(stn, stnlist) {
      int d;
      int f;
      f = 0;
      for (d = 0; d < 3; d++) {
         if (stn->leg[d]) {
            if (f) {
               printf("awooga - gap in legs\n");
            }
#ifdef DEBUG_ARTIC
            if (stn->leg[d]->l.reverse & FLAG_ARTICULATION) {
               node *stn2 = stn->leg[d]->l.to;
               printf("art: %ld %ld [%p] ", stn->colour, stn2->colour, stn);
               print_prefix(stn->name);
               printf(" - [%p] ", stn2);
               print_prefix(stn2->name);
               printf("\n");
            }
#endif
         } else {
            f = 1;
         }
      }
   }
#endif
   FOR_EACH_STN(stn, stnlist) {
      SVX_ASSERT(fixed(stn));
   }
}