cloud-sat/kissat-inc/src/collect.c

#define INLINE_SORT

#include "allocate.h"
#include "colors.h"
#include "collect.h"
#include "compact.h"
#include "inline.h"
#include "print.h"
#include "report.h"
#include "trail.h"
#include "sort.c"

#include <inttypes.h>

static void
flush_watched_clauses_by_literal (kissat * solver, litpairs * hyper,
				  unsigned lit, bool compact, reference start)
{
  assert (start != INVALID_REF);

  const value *values = solver->values;
  const assigned *all_assigned = solver->assigned;

  const value lit_value = values[lit];
  const assigned *lit_assigned = all_assigned + IDX (lit);
  const value lit_fixed = (lit_value && !lit_assigned->level) ? lit_value : 0;

  const unsigned mlit = kissat_map_literal (solver, lit, true);

  watches *lit_watches = &WATCHES (lit);
  watch *begin = BEGIN_WATCHES (*lit_watches), *q = begin;
  const watch *end_of_watches = END_WATCHES (*lit_watches), *p = q;

  while (p != end_of_watches)
    {
      watch head = *p++;
      if (head.type.binary)
	{
	  const unsigned other = head.binary.lit;
	  const unsigned other_idx = IDX (other);
	  const value other_value = values[other];
	  const value other_fixed =
	    (other_value && !all_assigned[other_idx].level) ? other_value : 0;
	  const unsigned mother = kissat_map_literal (solver, other, compact);
	  if (lit_fixed > 0 || other_fixed > 0 || mother == INVALID_LIT)
	    {
	      if (lit < other)
		kissat_delete_binary (solver,
				      head.binary.redundant,
				      head.binary.hyper, lit, other);
	    }
	  else
	    {
	      assert (!lit_fixed);
	      assert (!other_fixed);

	      if (head.binary.hyper)
		{
		  assert (head.binary.redundant);
		  assert (mlit != INVALID_LIT);
		  assert (mother != INVALID_LIT);
		  if (lit < other)
		    {
		      const litpair litpair = kissat_litpair (lit, other);
		      PUSH_STACK (*hyper, litpair);
		      LOGBINARY (lit, other, "saved SRC hyper");
		    }
		}
	      else
		{
		  head.binary.lit = mother;
		  *q++ = head;
#ifdef LOGGING
		  if (lit < other)
		    {
		      LOGBINARY (lit, other, "SRC");
		      LOGBINARY (mlit, mother, "DST");
		    }
#endif
		}
	    }
	}
      else
	{
	  assert (solver->watching);
	  const watch tail = *p++;
	  if (!lit_fixed)
	    {
	      const reference ref = tail.large.ref;
	      if (ref < start)
		{
		  *q++ = head;
		  *q++ = tail;
		}
	    }
	}
    }

  assert (!lit_fixed || q == begin);
  SET_END_OF_WATCHES (*lit_watches, q);
  LOG ("keeping %" SECTOR_FORMAT " watches[%u]", lit_watches->size, lit);

  if (!compact)
    return;

  if (mlit == INVALID_LIT)
    return;

  watches *mlit_watches = &WATCHES (mlit);
  if (lit_fixed)
    assert (!mlit_watches->size);
  else if (mlit < lit)
    {
      assert (mlit != INVALID_LIT);
      assert (mlit < lit);
      *mlit_watches = *lit_watches;
      LOG ("copied watches[%u] = watches[%u] "
	   "(size %" SECTOR_FORMAT ")", mlit, lit, mlit_watches->size);
      memset (lit_watches, 0, sizeof *lit_watches);
    }
  else
    assert (mlit == lit);
}

static void
flush_hyper_binary_watches (kissat * solver, litpairs * hyper, bool compact)
{
  assert (!solver->probing);
  const litpair *end = END_STACK (*hyper);
  const value *values = solver->values;
  size_t flushed = 0;
  for (const litpair * p = BEGIN_STACK (*hyper); p != end; p++)
    {
      const unsigned lit = p->lits[0];
      const unsigned other = p->lits[1];
      assert (lit < other);

      const value lit_value = values[lit];
      const value other_value = values[other];

      assert (!lit_value || LEVEL (lit));
      assert (!other_value || LEVEL (other));

      if (((lit_value < 0 && other_value > 0) ||
	   ((lit_value > 0 && other_value < 0))))
	{
	  LOGBINARY (lit, other, "keeping potential reason hyper SRC");
	  const unsigned mlit = kissat_map_literal (solver, lit, compact);
	  const unsigned mother = kissat_map_literal (solver, other, compact);
	  LOGBINARY (mlit, mother, "keeping potential reason hyper DST");
	  kissat_watch_other (solver, true, true, mlit, mother);
	  kissat_watch_other (solver, true, true, mother, mlit);
	}
      else
	{
	  LOGBINARY (lit, other, "flushing hyper SRC");
	  kissat_delete_binary (solver, true, true, lit, other);
	  flushed++;
	}
    }
  if (flushed)
    kissat_phase (solver, "collect",
		  GET (garbage_collections),
		  "flushed %zu unused hyper binary clauses %.0f%%",
		  flushed, kissat_percent (flushed, SIZE_STACK (*hyper)));
  (void) flushed;
}

static void
flush_all_watched_clauses (kissat * solver, bool compact, reference start)
{
  assert (solver->watching);
  LOG ("starting to flush watches at clause[%zu]", start);
  litpairs hyper;
  INIT_STACK (hyper);
  for (all_variables (idx))
    {
      const unsigned lit = LIT (idx);
      flush_watched_clauses_by_literal (solver, &hyper, lit, compact, start);
      const unsigned not_lit = NOT (lit);
      flush_watched_clauses_by_literal (solver, &hyper,
					not_lit, compact, start);
    }
  LOG ("saved %zu hyper binary watches", SIZE_STACK (hyper));
  flush_hyper_binary_watches (solver, &hyper, compact);
  RELEASE_STACK (hyper);
}

static void
update_large_reason (kissat * solver, assigned * assigned, unsigned forced,
		     clause * dst)
{
  assert (dst->reason);
  assert (forced != INVALID_LIT);
  reference dst_ref = kissat_reference_clause (solver, dst);
  const unsigned forced_idx = IDX (forced);
  struct assigned *a = assigned + forced_idx;
  assert (!a->binary);
  if (a->reason != dst_ref)
    {
      LOG ("reason reference %u of %s updated to %u",
	   a->reason, LOGLIT (forced), dst_ref);
      a->reason = dst_ref;
    }
  dst->reason = false;
}

static unsigned
get_forced (const value * values, clause * dst)
{
  assert (dst->reason);
  unsigned forced = INVALID_LIT;
  for (all_literals_in_clause (lit, dst))
    {
      const value value = values[lit];
      if (value <= 0)
	continue;
      forced = lit;
      break;
    }
  assert (forced != INVALID_LIT);
  return forced;
}

static void
get_forced_and_update_large_reason (kissat * solver, assigned * assigned,
				    const value * values, clause * dst)
{
  const unsigned forced = get_forced (values, dst);
  update_large_reason (solver, assigned, forced, dst);
}

static void
update_first_reducible (kissat * solver, const clause * end,
			clause * first_reducible)
{
  if (first_reducible >= end)
    {
      LOG ("first reducible after end of arena");
      solver->first_reducible = INVALID_REF;
    }
  else if (first_reducible)
    {
      LOGCLS (first_reducible, "updating first reducible clause to");
      solver->first_reducible =
	kissat_reference_clause (solver, first_reducible);
    }
  else
    {
      LOG ("first reducible clause becomes invalid");
      solver->first_reducible = INVALID_REF;
    }
}

static void
update_last_irredundant (kissat * solver, const clause * end,
			 clause * last_irredundant)
{
  if (!last_irredundant)
    {
      LOG ("no more large irredundant clauses left");
      solver->last_irredundant = INVALID_REF;
    }
  else if (end <= last_irredundant)
    {
      LOG ("last irredundant clause after end of arena");
      solver->last_irredundant = INVALID_REF;
    }
  else
    {
      LOGCLS (last_irredundant, "updating last irredundant clause to");
      reference ref = kissat_reference_clause (solver, last_irredundant);
      solver->last_irredundant = ref;
    }
}

static void
move_redundant_clauses_to_the_end (kissat * solver, reference ref)
{
  INC (moved);
  assert (ref != INVALID_REF);  
#ifndef NDEBUG
  const size_t size = SIZE_STACK (solver->arena);
  assert ((size_t) ref <= size);
#endif
  clause *begin = (clause *) (BEGIN_STACK (solver->arena) + ref);
  clause *end = (clause *) END_STACK (solver->arena);
  size_t bytes_redundant = (char *) end - (char *) begin;
  kissat_phase (solver, "move",
		GET (moved),
		"moving redundant clauses of %s to the end",
		FORMAT_BYTES (bytes_redundant));
  kissat_mark_reason_clauses (solver, ref);
  clause *redundant = (clause *) kissat_malloc (solver, bytes_redundant); 

  clause *p = begin, *q = begin, *r = redundant;

  const value *values = solver->values;
  assigned *assigned = solver->assigned;

  clause *last_irredundant = kissat_last_irredundant_clause (solver);  
  while (p != end)
    {
      assert (!p->shrunken);
      size_t bytes = kissat_bytes_of_clause (p->size);
      if (p->redundant)
	{
	  memcpy (r, p, bytes);
	  r = (clause *) (bytes + (char *) r);
	}
      else
	{
	  LOGCLS (p, "old DST");
	  memmove (q, p, bytes);
	  LOGCLS (q, "new DST");
	  last_irredundant = q;
	  if (q->reason)
	    get_forced_and_update_large_reason (solver, assigned, values, q);
	  q = (clause *) (bytes + (char *) q);
	}
      p = (clause *) (bytes + (char *) p);
    }
  r = redundant;
  clause *first_reducible = 0;
  while (q != end)
    {
      size_t bytes = kissat_bytes_of_clause (r->size);
      memcpy (q, r, bytes);
      LOGCLS (q, "new DST");
      if (q->reason)
	get_forced_and_update_large_reason (solver, assigned, values, q);
      assert (q->redundant);
      if (!first_reducible && !q->keep)
	first_reducible = q;
      r = (clause *) (bytes + (char *) r);
      q = (clause *) (bytes + (char *) q);
    }
  assert ((char *) r <= (char *) redundant + bytes_redundant);
  kissat_free (solver, redundant, bytes_redundant);

  assert (!first_reducible || first_reducible < q);

  update_first_reducible (solver, q, first_reducible);
  update_last_irredundant (solver, q, last_irredundant); 
}

static reference
sparse_sweep_garbage_clauses (kissat * solver, bool compact, reference start)
{
  assert (solver->watching);
  LOG ("sparse garbage collection starting at clause[%zu]", start);
#ifdef CHECKING_OR_PROVING
  const bool checking_or_proving = kissat_checking_or_proving (solver);
#endif
  assert (EMPTY_STACK (solver->added));
  assert (EMPTY_STACK (solver->removed));

  const value *values = solver->values;
  assigned *assigned = solver->assigned;

  size_t flushed_garbage_clauses = 0;
  size_t flushed_satisfied_clauses = 0;
  size_t flushed_literals = 0;

  clause *begin = (clause *) BEGIN_STACK (solver->arena);
  const clause *end = (clause *) END_STACK (solver->arena);

  clause *first, *src, *dst;
  if (start)
    first = kissat_dereference_clause (solver, start);
  else
    first = begin;
  src = dst = first;

  clause *first_redundant = 0;
  clause *first_reducible = 0;
  clause *last_irredundant;

  if (start)
    last_irredundant = kissat_last_irredundant_clause (solver);
  else
    last_irredundant = 0;

  size_t redundant_bytes = 0;

  for (clause * next; src != end; src = next)
    {
      if (src->garbage)
	{
	  next = kissat_delete_clause (solver, src);
	  flushed_garbage_clauses++;
	  if (last_irredundant == src)
	    {
	      if (first == begin)
		last_irredundant = 0;
	      else
		last_irredundant = first;
	    }
	  continue;
	}

      assert (src->size > 1);
      LOGCLS (src, "SRC");
      next = kissat_next_clause (src);
#if !defined(NDEBUG) || defined(CHECKING_OR_PROVING)
      const unsigned old_size = src->size;
#endif
      assert (SIZE_OF_CLAUSE_HEADER == sizeof (unsigned));
      *(unsigned *) dst = *(unsigned *) src;

      unsigned *q = dst->lits;

      unsigned mfirst = INVALID_LIT;
      unsigned msecond = INVALID_LIT;
      unsigned forced = INVALID_LIT;
      unsigned other = INVALID_LIT;
      unsigned non_false = 0;

      bool satisfied = false;

      for (all_literals_in_clause (lit, src))
	{
#ifdef CHECKING_OR_PROVING
	  if (checking_or_proving)
	    PUSH_STACK (solver->removed, lit);
#endif
	  if (satisfied)
	    continue;

	  const value tmp = values[lit];
	  const unsigned idx = IDX (lit);
	  const unsigned level = tmp ? assigned[idx].level : INVALID_LEVEL;

	  if (tmp < 0 && !level)
	    flushed_literals++;
	  else if (tmp > 0 && !level)
	    {
	      assert (!satisfied);
	      assert (!dst->reason);
	      LOG ("SRC satisfied by %s", LOGLIT (lit));
	      satisfied = true;
	    }
	  else
	    {
	      const unsigned mlit = kissat_map_literal (solver, lit, compact);

	      if (tmp > 0)
		{
		  assert (level);
		  forced = non_false++ ? INVALID_LIT : lit;
		}
	      else if (tmp < 0)
		other = lit;

	      if (mfirst == INVALID_LIT)
		mfirst = mlit;
	      else if (msecond == INVALID_LIT)
		msecond = mlit;

	      *q++ = mlit;

#ifdef CHECKING_OR_PROVING
	      if (checking_or_proving)
		PUSH_STACK (solver->added, lit);
#endif
	    }
	}

      if (satisfied)
	{
	  if (dst->redundant)
	    DEC (clauses_redundant);
	  else
	    DEC (clauses_irredundant);
	  if (dst->hyper)
	    DEC (hyper_ternaries);

	  flushed_satisfied_clauses++;

#ifdef CHECKING_OR_PROVING
	  if (checking_or_proving)
	    {
	      REMOVE_CHECKER_STACK (solver->removed);
	      DELETE_STACK_FROM_PROOF (solver->removed);
	      CLEAR_STACK (solver->added);
	      CLEAR_STACK (solver->removed);
	    }
#endif
	  if (last_irredundant == src)
	    {
	      if (first == begin)
		last_irredundant = 0;
	      else
		last_irredundant = first;
	    }
	  continue;
	}

      const unsigned new_size = q - dst->lits;
      assert (new_size <= old_size);
      assert (1 < new_size);

      if (new_size == 2)
	{
	  assert (mfirst != INVALID_LIT);
	  assert (msecond != INVALID_LIT);

	  const bool redundant = dst->redundant;
	  LOGBINARY (mfirst, msecond, "DST");
	  kissat_watch_binary (solver, redundant, false, mfirst, msecond);

	  if (dst->hyper)
	    DEC (hyper_ternaries);

	  if (dst->reason)
	    {
	      assert (non_false == 1);
	      assert (other != INVALID_LIT);
	      assert (forced != INVALID_LIT);

	      const unsigned forced_idx = IDX (forced);
	      struct assigned *a = assigned + forced_idx;
	      assert (!a->binary);

	      LOGBINARY (mfirst, msecond,
			 "reason clause[%u] of %s updated to binary reason",
			 a->reason, LOGLIT (forced));

	      a->binary = true;
	      a->reason = other;
	    }

	  if (!redundant && last_irredundant == src)
	    {
	      if (first == begin)
		last_irredundant = 0;
	      else
		last_irredundant = first;
	    }
	}
      else
	{
	  assert (2 < new_size);

	  dst->size = new_size;
	  dst->shrunken = false;
	  dst->searched = 2;

	  LOGCLS (dst, "DST");
	  if (dst->reason)
	    update_large_reason (solver, assigned, forced, dst);

	  clause *next_dst = kissat_next_clause (dst);

	  if (dst->redundant)
	    {
	      if (!first_reducible && !dst->keep)
		first_reducible = dst;

	      redundant_bytes += (char *) next_dst - (char *) dst;
	      if (!first_redundant)
		first_redundant = dst;
	    }
	  else
	    last_irredundant = dst;

	  dst = next_dst;
	}

#ifdef CHECKING_OR_PROVING
      if (!checking_or_proving)
	continue;

      if (new_size != old_size)
	{
	  assert (1 < new_size);
	  assert (new_size < old_size);

	  CHECK_AND_ADD_STACK (solver->added);
	  ADD_STACK_TO_PROOF (solver->added);

	  REMOVE_CHECKER_STACK (solver->removed);
	  DELETE_STACK_FROM_PROOF (solver->removed);
	}
      CLEAR_STACK (solver->added);
      CLEAR_STACK (solver->removed);
#endif
    }

  update_first_reducible (solver, dst, first_reducible);
  update_last_irredundant (solver, dst, last_irredundant);

  if (first_redundant)
    LOGCLS (first_redundant, "determined first redundant clause as");

#if !defined(QUIET) || !defined(NMETRICS)
  size_t bytes = (char *) END_STACK (solver->arena) - (char *) dst;
#endif
#ifndef QUIET
  if (flushed_literals)
    kissat_phase (solver, "collect",
		  GET (garbage_collections),
		  "flushed %zu falsified literals in large clauses",
		  flushed_literals);
  size_t flushed_clauses =
    flushed_satisfied_clauses + flushed_garbage_clauses;
  if (flushed_satisfied_clauses)
    kissat_phase (solver, "collect",
		  GET (garbage_collections),
		  "flushed %zu satisfied large clauses %.0f%%",
		  flushed_satisfied_clauses,
		  kissat_percent (flushed_satisfied_clauses,
				  flushed_clauses));
  if (flushed_garbage_clauses)
    kissat_phase (solver, "collect",
		  GET (garbage_collections),
		  "flushed %zu large garbage clauses %.0f%%",
		  flushed_garbage_clauses,
		  kissat_percent (flushed_garbage_clauses, flushed_clauses));
  kissat_phase (solver, "collect",
		GET (garbage_collections),
		"collected %s in total", FORMAT_BYTES (bytes));
#endif
  ADD (literals_flushed, flushed_literals);
#ifndef NMETRICS
  ADD (allocated_collected, bytes);
#endif

  reference res = INVALID_REF;

  if (first_redundant &&
      last_irredundant && first_redundant < last_irredundant)
    {
#ifdef LOGGING
      size_t move_bytes = (char *) dst - (char *) first_redundant;
      LOG ("redundant bytes %s (%.0f%) out of %s moving bytes",
	   FORMAT_BYTES (redundant_bytes),
	   kissat_percent (redundant_bytes, move_bytes),
	   FORMAT_BYTES (move_bytes));
#endif
      assert (first_redundant < dst);
      res = kissat_reference_clause (solver, first_redundant);
      assert (res != INVALID_REF);
    }

  SET_END_OF_STACK (solver->arena, (word *) dst);
  kissat_shrink_arena (solver);

  kissat_clear_clueue (solver, &solver->clueue);

#ifndef NMETRICS
  if (solver->statistics.arena_garbage)
    kissat_very_verbose (solver, "still %s garbage left in arena",
			 FORMAT_BYTES (solver->statistics.arena_garbage));
  else
    kissat_very_verbose (solver, "all garbage clauses in arena collected");
#endif

  return res;
}

static void
rewatch_clauses (kissat * solver, reference start)
{
  LOG ("rewatching clause[%zu] and following clauses", start);
  assert (solver->watching);

  const value *values = solver->values;
  const assigned *assigned = solver->assigned;
  watches *watches = solver->watches;
  const word *arena = BEGIN_STACK (solver->arena);

  clause *end = (clause *) END_STACK (solver->arena);
  clause *c = (clause *) (BEGIN_STACK (solver->arena) + start);
  assert (c <= end);

  for (clause * next; c != end; c = next)
    {
      next = kissat_next_clause (c);

      unsigned *lits = c->lits;
      kissat_sort_literals (solver, values, assigned, c->size, lits);
      c->searched = 2;

      const reference ref = (word *) c - arena;
      const unsigned l0 = lits[0];
      const unsigned l1 = lits[1];

      kissat_push_blocking_watch (solver, watches + l0, l1, ref);
      kissat_push_blocking_watch (solver, watches + l1, l0, ref);
    }
}

void
kissat_sparse_collect (kissat * solver, bool compact, reference start)
{
  assert (solver->watching);
  START (collect);
  INC (garbage_collections);
  INC (sparse_garbage_collections);
  REPORT (1, 'G');
  unsigned vars, mfixed;     
  if (compact)
    vars = kissat_compact_literals (solver, &mfixed);
  else
    {
      vars = solver->vars;
      mfixed = INVALID_LIT;
    }      
  flush_all_watched_clauses (solver, compact, start); 
  reference move = sparse_sweep_garbage_clauses (solver, compact, start);
  if (compact)
    kissat_finalize_compacting (solver, vars, mfixed);  
  if (move != INVALID_REF)
    move_redundant_clauses_to_the_end (solver, move); 
 
  rewatch_clauses (solver, start);  
  REPORT (1, 'C');
  kissat_check_statistics (solver);
  STOP (collect);
}

static void
dense_sweep_garbage_clauses (kissat * solver)
{
  assert (!solver->level);
  assert (!solver->watching);

  LOG ("dense garbage collection");

  size_t flushed_garbage_clauses = 0;

  clause *first_reducible = 0;
  clause *last_irredundant = 0;

  clause *begin = (clause *) BEGIN_STACK (solver->arena);
  const clause *end = (clause *) END_STACK (solver->arena);

  clause *src = begin;
  clause *dst = src;

  for (clause * next; src != end; src = next)
    {
      if (src->garbage)
	{
	  next = kissat_delete_clause (solver, src);
	  flushed_garbage_clauses++;
	  continue;
	}
      assert (src->size > 1);
      LOGCLS (src, "SRC");
      next = kissat_next_clause (src);
      assert (SIZE_OF_CLAUSE_HEADER == sizeof (unsigned));
      *(unsigned *) dst = *(unsigned *) src;
      dst->searched = src->searched;
      dst->size = src->size;
      dst->shrunken = false;
      memmove (dst->lits, src->lits, src->size * sizeof (unsigned));
      LOGCLS (dst, "DST");
      if (!dst->redundant)
	last_irredundant = dst;
      else if (!first_reducible && !dst->keep)
	first_reducible = dst;
      dst = kissat_next_clause (dst);
    }

  update_first_reducible (solver, dst, first_reducible);
  update_last_irredundant (solver, dst, last_irredundant);

#if !defined(QUIET) || !defined(NMETRICS)
  size_t bytes = (char *) END_STACK (solver->arena) - (char *) dst;
#endif
  kissat_phase (solver, "collect",
		GET (garbage_collections),
		"flushed %zu large garbage clauses", flushed_garbage_clauses);
  kissat_phase (solver, "collect",
		GET (garbage_collections),
		"collected %s in total", FORMAT_BYTES (bytes));
#ifndef NMETRICS
  ADD (allocated_collected, bytes);
#endif

  SET_END_OF_STACK (solver->arena, (word *) dst);
  kissat_shrink_arena (solver);

  kissat_clear_clueue (solver, &solver->clueue);
#ifndef NMETRICS
  if (solver->statistics.arena_garbage)
    kissat_very_verbose (solver, "still %s garbage left in arena",
			 FORMAT_BYTES (solver->statistics.arena_garbage));
  else
    kissat_very_verbose (solver, "all garbage clauses in arena collected");
#endif
}

void
kissat_dense_collect (kissat * solver)
{
  assert (!solver->watching);
  assert (!solver->level);
  START (collect);
  INC (garbage_collections);
  INC (dense_garbage_collections);
  REPORT (1, 'G');
  dense_sweep_garbage_clauses (solver);
  REPORT (1, 'C');
  STOP (collect);
}