/*************************************************************************
*									 *
*	 YAP Prolog 							 *
*									 *
*	Yap Prolog was developed at NCCUP - Universidade do Porto	 *
*									 *
* Copyright L.Damas, V.S.Costa and Universidade do Porto 1985-1997	 *
*									 *
**************************************************************************
*									 *
* File:		non backtrackable term support				 *
* Last rev:	2/8/06							 *
* mods:									 *
* comments:	non-backtrackable term support				 *
*									 *
*************************************************************************/
#ifdef SCCS
static char SccsId[] = "%W% %G%";
#endif

#include "Yap.h"
#include "Yatom.h"
#include "YapHeap.h"
#include "yapio.h"
#include "iopreds.h"
#include "eval.h"
#include "attvar.h"
#include <math.h>

/* Non-backtrackable terms will from now on be stored on arenas, a
   special term on the heap. Arenas automatically contract as we add terms to
   the front.

 */

#define QUEUE_FUNCTOR_ARITY 4

#define QUEUE_ARENA 0
#define QUEUE_HEAD 1
#define QUEUE_TAIL 2
#define QUEUE_SIZE 3

#define HEAP_FUNCTOR_MIN_ARITY

#define HEAP_SIZE  0
#define HEAP_MAX   1
#define HEAP_ARENA 2
#define HEAP_START 3

#define MIN_ARENA_SIZE 1048
#define MAX_ARENA_SIZE (2048*16)

#define Global_MkIntegerTerm(I) MkIntegerTerm(I)

static UInt
big2arena_sz(CELL *arena_base)
{
  return (((MP_INT*)(arena_base+2))->_mp_alloc*sizeof(mp_limb_t) + sizeof(MP_INT) + sizeof(Functor)+2*sizeof(CELL))/sizeof(CELL);
}

static UInt
arena2big_sz(UInt sz)
{
  return sz - (sizeof(MP_INT) + sizeof(Functor) + 2*sizeof(CELL))/sizeof(CELL);
}


/* pointer to top of an arena */
static inline CELL *
ArenaLimit(Term arena)
{
  CELL *arena_base = RepAppl(arena);
  UInt sz = big2arena_sz(arena_base);
  return arena_base+sz;
}

/* pointer to top of an arena */
static inline CELL *
ArenaPt(Term arena)
{
  return (CELL *)RepAppl(arena);
}

static inline UInt
ArenaSz(Term arena)
{
  return big2arena_sz(RepAppl(arena));
}

static Term
CreateNewArena(CELL *ptr, UInt size)
{
  Term t = AbsAppl(ptr);
  MP_INT *dst;

  ptr[0] = (CELL)FunctorBigInt;
  ptr[1] = EMPTY_ARENA;
  dst = (MP_INT *)(ptr+2);
  dst->_mp_size = 0L;
  dst->_mp_alloc = (sizeof(CELL)/sizeof(mp_limb_t))*arena2big_sz(size);
  ptr[size-1] = EndSpecials;
  return t;
}

static Term
NewArena(UInt size, UInt arity, CELL *where USES_REGS)
{
  Term t;
  UInt new_size;

  if (where == NULL || where == H) {
    while (H+size > ASP-1024) {
      if (!Yap_gcl(size*sizeof(CELL), arity, ENV, P)) {
	Yap_Error(OUT_OF_STACK_ERROR, TermNil, LOCAL_ErrorMessage);
	return TermNil;
      }
    }
    t = CreateNewArena(H, size);
    H += size;
  } else {
    if ((new_size=Yap_InsertInGlobal(where, size*sizeof(CELL)))==0) {
      Yap_Error(OUT_OF_STACK_ERROR,TermNil,"No Stack Space for Non-Backtrackable terms");
      return TermNil;
    }
    size = new_size/sizeof(CELL);
    t = CreateNewArena(where, size);
  }
  return t;
}

static Int
p_allocate_arena( USES_REGS1 )
{
  Term t = Deref(ARG1);
  if (IsVarTerm(t)) {
    Yap_Error(INSTANTIATION_ERROR,t,"allocate_arena");
    return FALSE;
  } else if (!IsIntegerTerm(t)) {
      Yap_Error(TYPE_ERROR_INTEGER,t,"allocate_arena");
      return FALSE;
  }
  return Yap_unify(ARG2,NewArena(IntegerOfTerm(t), 1, NULL PASS_REGS));
}


static Int
p_default_arena_size( USES_REGS1 )
{
  return Yap_unify(ARG1,MkIntegerTerm(ArenaSz(LOCAL_GlobalArena)));
}


void
Yap_AllocateDefaultArena(Int gsize, Int attsize, int wid)
{
  CACHE_REGS
    REMOTE_GlobalArena(wid) = NewArena(gsize, 2, NULL PASS_REGS);
}

static void
adjust_cps(UInt size USES_REGS)
{
  /* adjust possible back pointers in choice-point stack */
  choiceptr b_ptr = B;
  while (b_ptr->cp_h == H) {
    b_ptr->cp_h += size;
    b_ptr = b_ptr->cp_b;
  }
}


static int
GrowArena(Term arena, CELL *pt, UInt old_size, UInt size, UInt arity USES_REGS)
{
  LOCAL_ArenaOverflows++;
  if (size == 0) {
    if (old_size < 128*1024) {
      size = old_size;
    } else {
      size = old_size+128*1024;
    }
  }
  if (size < 4096) {
    size = 4096;
  }
  if (pt == H) {
    if (H+size > ASP-1024) {

      XREGS[arity+1] = arena;
      if (!Yap_gcl(size*sizeof(CELL), arity+1, ENV, gc_P(P,CP))) {
	Yap_Error(OUT_OF_STACK_ERROR, TermNil, LOCAL_ErrorMessage);
	return FALSE;
      }
      arena = XREGS[arity+1];
      /* we don't know if the GC added junk on top of the global */
      pt = ArenaLimit(arena);
      return GrowArena(arena, pt, old_size, size, arity PASS_REGS);
    }
    adjust_cps(size PASS_REGS);
    H += size;
  } else {
    XREGS[arity+1] = arena;
    /* try to recover some room  */
    if (arena == LOCAL_GlobalArena && 10*(pt-H0) > 8*(H-H0)) {
      if (!Yap_gcl(size*sizeof(CELL), arity+1, ENV, gc_P(P,CP))) {
	Yap_Error(OUT_OF_STACK_ERROR,TermNil,LOCAL_ErrorMessage);
	return FALSE;
      }
    }
    arena = XREGS[arity+1];
    pt = ArenaLimit(arena);
    if ((size=Yap_InsertInGlobal(pt, size*sizeof(CELL)))==0) {
      return FALSE;
    }
    size = size/sizeof(CELL);
    arena = XREGS[arity+1];
  }
  CreateNewArena(ArenaPt(arena), size+old_size);
  return TRUE;
}

CELL *
Yap_GetFromArena(Term *arenap, UInt cells, UInt arity)
{
  CACHE_REGS
 restart:
  {
    Term arena = *arenap;
    CELL *max = ArenaLimit(arena);
    CELL *base = ArenaPt(arena);
    CELL *newH;
    UInt old_sz = ArenaSz(arena), new_size;

    if (IN_BETWEEN(base, H, max)) {
      base = H;
      H += cells;
      return base;
    }
    if (base+cells > max-1024) {
      if (!GrowArena(arena, max, old_sz, old_sz+sizeof(CELL)*1024, arity PASS_REGS))
	return NULL;
      goto restart;
    }

    newH = base+cells;
    new_size = old_sz - cells;
    *arenap = CreateNewArena(newH, new_size);
    return base;
  }
}

static void
CloseArena(CELL *oldH, CELL *oldHB, CELL *oldASP, Term *oldArenaP, UInt old_size USES_REGS)
{
  UInt new_size;

  if (H == oldH)
    return;
  new_size = old_size - (H-RepAppl(*oldArenaP));
  *oldArenaP = CreateNewArena(H, new_size);
  H = oldH;
  HB = oldHB;
  ASP = oldASP;
}

static inline void
clean_dirty_tr(tr_fr_ptr TR0 USES_REGS) {
  if (TR != TR0) {
    tr_fr_ptr pt = TR0;

    do {
      Term p = TrailTerm(pt++);
      if (IsVarTerm(p)) {
	RESET_VARIABLE(p);
      } else {
	/* copy downwards */
	TrailTerm(TR0+1) = TrailTerm(pt);
	TrailTerm(TR0) = TrailTerm(TR0+2) = p;
	pt+=2;
	TR0 += 3;
      }
    } while (pt != TR);
    TR = TR0;
  }
}

static int
copy_complex_term(register CELL *pt0, register CELL *pt0_end, int share, int copy_att_vars, CELL *ptf, CELL *HLow USES_REGS)
{

  struct cp_frame *to_visit0, *to_visit = (struct cp_frame *)Yap_PreAllocCodeSpace();
  CELL *HB0 = HB;
  tr_fr_ptr TR0 = TR;
  int ground = TRUE;

  HB = HLow;
  to_visit0 = to_visit;
 loop:
  while (pt0 < pt0_end) {
    register CELL d0;
    register CELL *ptd0;
    ++ pt0;
    ptd0 = pt0;
    d0 = *ptd0;
    deref_head(d0, copy_term_unk);
  copy_term_nvar:
    {
      if (IsPairTerm(d0)) {
	CELL *ap2 = RepPair(d0);
	if ((share && ap2 < HB) ||
	    (ap2 >= HB && ap2 < H)) {
	  /* If this is newer than the current term, just reuse */
	  *ptf++ = d0;
	  continue;
	} 
	*ptf = AbsPair(H);
	ptf++;
#ifdef RATIONAL_TREES
	if (to_visit+1 >= (struct cp_frame *)AuxSp) {
	  goto heap_overflow;
	}
	to_visit->start_cp = pt0;
	to_visit->end_cp = pt0_end;
	to_visit->to = ptf;
	to_visit->oldv = *pt0;
	to_visit->ground = ground;
	/* fool the system into thinking we had a variable there */
	*pt0 = AbsPair(H);
	to_visit ++;
#else
	if (pt0 < pt0_end) {
	  if (to_visit + 1 >= (CELL **)AuxSp) {
	    goto heap_overflow;
	  }
	  to_visit->start_cp = pt0;
	  to_visit->end_cp = pt0_end;
	  to_visit->to = ptf;
	  to_visit->ground = ground;
	  to_visit ++;
	}
#endif
	ground = TRUE;
	pt0 = ap2 - 1;
	pt0_end = ap2 + 1;
	ptf = H;
	H += 2;
	if (H > ASP - MIN_ARENA_SIZE) {
	  goto overflow;
	}
      } else if (IsApplTerm(d0)) {
	register Functor f;
	register CELL *ap2;
	/* store the terms to visit */
	ap2 = RepAppl(d0);
	if ((share && ap2 < HB) ||
	    (ap2 >= HB && ap2 < H)) {
	  /* If this is newer than the current term, just reuse */
	  *ptf++ = d0;
	  continue;
	} 
	f = (Functor)(*ap2);

	if (IsExtensionFunctor(f)) {
	  switch((CELL)f) {
	  case (CELL)FunctorDBRef:
	  case (CELL)FunctorAttVar:
	    *ptf++ = d0;
	    break;
	  case (CELL)FunctorLongInt:
	    if (H > ASP - (MIN_ARENA_SIZE+3)) {
	      goto overflow;
	    }
	    *ptf++ = AbsAppl(H);
	    H[0] = (CELL)f;
	    H[1] = ap2[1];
	    H[2] = EndSpecials;
	    H += 3;
	    if (H > ASP - MIN_ARENA_SIZE) {
	      goto overflow;
	    }
	    break;
	  case (CELL)FunctorDouble:
	    if (H > ASP - (MIN_ARENA_SIZE+(2+SIZEOF_DOUBLE/sizeof(CELL)))) {
	      goto overflow;
	    }
	    *ptf++ = AbsAppl(H);
	    H[0] = (CELL)f;
	    H[1] = ap2[1];
#if SIZEOF_DOUBLE == 2*SIZEOF_LONG_INT
	    H[2] = ap2[2];
	    H[3] = EndSpecials;
	    H += 4;
#else
	    H[2] = EndSpecials;
	    H += 3;
#endif
	    break;
	  default:
	    {
	      /* big int */
	      UInt sz = (sizeof(MP_INT)+3*CellSize+
			 ((MP_INT *)(ap2+2))->_mp_alloc*sizeof(mp_limb_t))/CellSize, i;

	      if (H > ASP - (MIN_ARENA_SIZE+sz)) {
		goto overflow;
	      }
	      *ptf++ = AbsAppl(H);
	      H[0] = (CELL)f;
	      for (i = 1; i < sz; i++) {
		H[i] = ap2[i];
	      }
	      H += sz;
	    }
	  }
	  continue;
	}
	*ptf = AbsAppl(H);
	ptf++;
	/* store the terms to visit */
#ifdef RATIONAL_TREES
	if (to_visit+1 >= (struct cp_frame *)AuxSp) {
	  goto heap_overflow;
	}
	to_visit->start_cp = pt0;
	to_visit->end_cp = pt0_end;
	to_visit->to = ptf;
	to_visit->oldv = *pt0;
	to_visit->ground = ground;
	/* fool the system into thinking we had a variable there */
	*pt0 = AbsAppl(H);
	to_visit ++;
#else
	if (pt0 < pt0_end) {
	  if (to_visit ++ >= (CELL **)AuxSp) {
	    goto heap_overflow;
	  }
	  to_visit->start_cp = pt0;
	  to_visit->end_cp = pt0_end;
	  to_visit->to = ptf;
	  to_visit->ground = ground;
	  to_visit ++;
	}
#endif
	ground = (f != FunctorMutable);
	d0 = ArityOfFunctor(f);
	pt0 = ap2;
	pt0_end = ap2 + d0;
	/* store the functor for the new term */
	H[0] = (CELL)f;
	ptf = H+1;
	H += 1+d0;
	if (H > ASP - MIN_ARENA_SIZE) {
	  goto overflow;
	}
      } else {
	/* just copy atoms or integers */
	*ptf++ = d0;
      }
      continue;
    }

    derefa_body(d0, ptd0, copy_term_unk, copy_term_nvar);
    ground = FALSE;
    /* don't need to copy variables if we want to share the global term */
    if ((share && ptd0 < HB && ptd0 > H0) ||
	(ptd0 >= HLow && ptd0 < H)) { 
      /* we have already found this cell */
      *ptf++ = (CELL) ptd0;
    } else {
#if COROUTINING
      if (copy_att_vars && GlobalIsAttachedTerm((CELL)ptd0)) {
	/* if unbound, call the standard copy term routine */
	struct cp_frame *bp;
	CELL new;

	bp = to_visit;
	if (!GLOBAL_attas[ExtFromCell(ptd0)].copy_term_op(ptd0, &bp, ptf PASS_REGS)) {
	  goto overflow;
	}
	to_visit = bp;
	new = *ptf;
	if (TR > (tr_fr_ptr)LOCAL_TrailTop - 256) {
	  /* Trail overflow */
	  if (!Yap_growtrail((TR-TR0)*sizeof(tr_fr_ptr *), TRUE)) {
	    goto trail_overflow;
	  }
	}
	Bind_and_Trail(ptd0, new);
	ptf++;
      } else {
#endif
	/* first time we met this term */
	RESET_VARIABLE(ptf);
	if ((ADDR)TR > LOCAL_TrailTop-MIN_ARENA_SIZE)
	  goto trail_overflow;
	Bind_and_Trail(ptd0, (CELL)ptf);
	ptf++;
#ifdef COROUTINING
      }
#endif
    }
  }

  /* Do we still have compound terms to visit */
  if (to_visit > to_visit0) {
    to_visit --;
    pt0 = to_visit->start_cp;
    pt0_end = to_visit->end_cp;
    ptf = to_visit->to;
#ifdef RATIONAL_TREES
    *pt0 = to_visit->oldv;
#endif
    ground = (ground && to_visit->ground);
    goto loop;
  }

  /* restore our nice, friendly, term to its original state */
  HB = HB0;
  clean_dirty_tr(TR0 PASS_REGS);
  /* follow chain of multi-assigned variables */
  return 0;

 overflow:
  /* oops, we're in trouble */
  H = HLow;
  /* we've done it */
  /* restore our nice, friendly, term to its original state */
  HB = HB0;
#ifdef RATIONAL_TREES
  while (to_visit > to_visit0) {
    to_visit --;
    pt0 = to_visit->start_cp;
    pt0_end = to_visit->end_cp;
    ptf = to_visit->to;
    *pt0 = to_visit->oldv;
  }
#endif
  reset_trail(TR0);
  return -1;

 heap_overflow:
  /* oops, we're in trouble */
  H = HLow;
  /* we've done it */
  /* restore our nice, friendly, term to its original state */
  HB = HB0;
#ifdef RATIONAL_TREES
  while (to_visit > to_visit0) {
    to_visit--;
    pt0 = to_visit->start_cp;
    pt0_end = to_visit->end_cp;
    ptf = to_visit->to;
    *pt0 = to_visit->oldv;
  }
#endif
  reset_trail(TR0);
  return -2;

 trail_overflow:
  /* oops, we're in trouble */
  H = HLow;
  /* we've done it */
  /* restore our nice, friendly, term to its original state */
  HB = HB0;
#ifdef RATIONAL_TREES
  while (to_visit > to_visit0) {
    to_visit--;
    pt0 = to_visit->start_cp;
    pt0_end = to_visit->end_cp;
    ptf = to_visit->to;
    *pt0 = to_visit->oldv;
  }
#endif
  reset_trail(TR0);
  return -4;
}

static Term
CopyTermToArena(Term t, Term arena, int share, int copy_att_vars, UInt arity, Term *newarena, UInt min_grow USES_REGS)
{
  UInt old_size = ArenaSz(arena);
  CELL *oldH = H;
  CELL *oldHB = HB;
  CELL *oldASP = ASP;
  int res = 0;
  Term tn;

 restart:
  t = Deref(t);
  if (IsVarTerm(t)) {
    ASP = ArenaLimit(arena);
    H = HB = ArenaPt(arena);
#if COROUTINING
    if (GlobalIsAttachedTerm(t)) {
      CELL *Hi;

      *H = t;
      Hi = H+1;
      H += 2;
      if ((res = copy_complex_term(Hi-2, Hi-1, share, copy_att_vars, Hi, Hi PASS_REGS)) < 0) 
	goto error_handler;
      CloseArena(oldH, oldHB, oldASP, newarena, old_size PASS_REGS);
      return Hi[0];
    }
#endif
    if (share && VarOfTerm(t) > ArenaPt(arena)) {
      CloseArena(oldH, oldHB, oldASP, newarena, old_size PASS_REGS);
      return t;
    }
    tn = MkVarTerm();
    if (H > ASP - MIN_ARENA_SIZE) {
      res = -1;
      goto error_handler;
    }
    CloseArena(oldH, oldHB, oldASP, newarena, old_size PASS_REGS);
    return tn;
  } else if (IsAtomOrIntTerm(t)) {
    return t;
  } else if (IsPairTerm(t)) {
    Term tf;
    CELL *ap;
    CELL *Hi;

    if (share && ArenaPt(arena) > RepPair(t)) {
      return t;
    }
    H = HB = ArenaPt(arena);
    ASP = ArenaLimit(arena);
    ap = RepPair(t);
    Hi = H;
    tf = AbsPair(H);
    H += 2;
    if ((res = copy_complex_term(ap-1, ap+1, share, copy_att_vars, Hi, Hi PASS_REGS)) < 0) {
	goto error_handler;
    }
    CloseArena(oldH, oldHB, oldASP, newarena, old_size PASS_REGS);
    return tf;
  } else {
    Functor f;
    Term tf;
    CELL *HB0;
    CELL *ap;

    if (share && ArenaPt(arena) > RepAppl(t)) {
      return t;
    }
    H = HB = ArenaPt(arena);
    ASP = ArenaLimit(arena);
    f = FunctorOfTerm(t);
    HB0 = H;
    ap = RepAppl(t);
    tf = AbsAppl(H);
    H[0] = (CELL)f;
    if (IsExtensionFunctor(f)) {
      switch((CELL)f) {
      case (CELL)FunctorDBRef:
	CloseArena(oldH, oldHB, oldASP, newarena, old_size PASS_REGS);
	return t;
      case (CELL)FunctorLongInt:
	if (H > ASP - (MIN_ARENA_SIZE+3)) {
	  res = -1;
	  goto error_handler;
	}
	H[1] = ap[1];
	H[2] = EndSpecials;
	H += 3;
	break;
      case (CELL)FunctorDouble:
	if (H > ASP - (MIN_ARENA_SIZE+(2+SIZEOF_DOUBLE/sizeof(CELL)))) {
	  res = -1;
	  goto error_handler;
	}
	H[1] = ap[1];
#if SIZEOF_DOUBLE == 2*SIZEOF_LONG_INT
	H[2] = ap[2];
	H[3] = EndSpecials;
	H += 4;
#else
	H[2] = EndSpecials;
	H += 3;
#endif
	break;
      default:
	{
	  UInt sz = ArenaSz(t), i;

	  if (H > ASP - (MIN_ARENA_SIZE+sz)) {
	    res = -1;
	    goto error_handler;
	  }
	  for (i = 1; i < sz; i++) {
	    H[i] = ap[i];
	  }
	  H += sz;
	}
      }
    } else {
      H += 1+ArityOfFunctor(f);
      if (H > ASP-MIN_ARENA_SIZE) {
	res = -1;
	goto error_handler;
      } 
      if ((res = copy_complex_term(ap, ap+ArityOfFunctor(f), share, copy_att_vars, HB0+1, HB0 PASS_REGS)) < 0) {
	goto error_handler;
      }
    }
    CloseArena(oldH, oldHB, oldASP, newarena, old_size PASS_REGS);
    return tf;
  }
 error_handler:
  H = HB;
  CloseArena(oldH, oldHB, oldASP, newarena, old_size PASS_REGS);
  XREGS[arity+1] = t;
  XREGS[arity+2] = arena;
  XREGS[arity+3] = (CELL)newarena;
  {
    CELL *old_top = ArenaLimit(*newarena);
    ASP = oldASP;
    H = oldH;
    HB = oldHB;
    switch (res) {
    case -1:
      if (arena == LOCAL_GlobalArena)
	LOCAL_GlobalArenaOverflows++;
      if (!GrowArena(arena, old_top, old_size, min_grow, arity+3 PASS_REGS)) {
	Yap_Error(OUT_OF_STACK_ERROR, TermNil, LOCAL_ErrorMessage);
	return 0L;
      }
      break;
    default: /* temporary space overflow */
      if (!Yap_ExpandPreAllocCodeSpace(0,NULL,TRUE)) {
	Yap_Error(OUT_OF_AUXSPACE_ERROR, TermNil, LOCAL_ErrorMessage);
	return 0L;
      }
    }
  }
  oldH = H;
  oldHB = HB;
  oldASP = ASP;
  newarena = (CELL *)XREGS[arity+3];
  arena = Deref(XREGS[arity+2]);
  t = XREGS[arity+1];
  old_size = ArenaSz(arena);
  goto restart;
}

static Term
CreateTermInArena(Term arena, Atom Na, UInt Nar, UInt arity, Term *newarena, Term init USES_REGS)
{
  UInt old_size = ArenaSz(arena);
  CELL *oldH = H;
  CELL *oldHB = HB;
  CELL *oldASP = ASP;
  Term tf;
  CELL *HB0;
  Functor f = Yap_MkFunctor(Na, Nar);
  UInt i;

 restart:
  H = HB = ArenaPt(arena);
  ASP = ArenaLimit(arena);
  HB0 = H;
  tf = AbsAppl(H);
  H[0] = (CELL)f;
  H += 1+ArityOfFunctor(f);
  if (H > ASP-MIN_ARENA_SIZE) {
    /* overflow */
    H = HB;
    CloseArena(oldH, oldHB, oldASP, newarena, old_size PASS_REGS);
    XREGS[arity+1] = arena;
    XREGS[arity+2] = (CELL)newarena;
    {
      CELL *old_top = ArenaLimit(*newarena);
      ASP = oldASP;
      H = oldH;
      HB = oldHB;
      if (arena == LOCAL_GlobalArena)
	LOCAL_GlobalArenaOverflows++;
      if (!GrowArena(arena, old_top, old_size, Nar*sizeof(CELL), arity+2 PASS_REGS)) {
	Yap_Error(OUT_OF_STACK_ERROR, TermNil, "while creating large global term");
	return 0L;
      }
    }
    oldH = H;
    oldHB = HB;
    oldASP = ASP;
    newarena = (CELL *)XREGS[arity+2];
    arena = Deref(XREGS[arity+1]);
    old_size = ArenaSz(arena);
    goto restart;
  } 
  if (init == 0L) {
    for (i=1; i<=Nar; i++) {
      RESET_VARIABLE(HB0+i);
    }
  } else {
    for (i=1; i<=Nar; i++) {
      HB0[i] = init;
    }
  }
  CloseArena(oldH, oldHB, oldASP, newarena, old_size PASS_REGS);
  return tf;
}

inline static GlobalEntry *
FindGlobalEntry(Atom at USES_REGS)
/* get predicate entry for ap/arity; create it if neccessary.              */
{
  Prop p0;
  AtomEntry *ae = RepAtom(at);

  READ_LOCK(ae->ARWLock);
  p0 = ae->PropsOfAE;
  while (p0) {
    GlobalEntry *pe = RepGlobalProp(p0);
    if ( pe->KindOfPE == GlobalProperty
#if THREADS
	 && pe->owner_id == worker_id
#endif
	 ) {
      READ_UNLOCK(ae->ARWLock);
      return pe;
    }
    p0 = pe->NextOfPE;
  }
  READ_UNLOCK(ae->ARWLock);
  return NULL;
}

inline static GlobalEntry *
GetGlobalEntry(Atom at USES_REGS)
/* get predicate entry for ap/arity; create it if neccessary.              */
{
  Prop p0;
  AtomEntry *ae = RepAtom(at);
  GlobalEntry *new;

  WRITE_LOCK(ae->ARWLock);
  p0 = ae->PropsOfAE;
  while (p0) {
    GlobalEntry *pe = RepGlobalProp(p0);
    if ( pe->KindOfPE == GlobalProperty
#if THREADS
	 && pe->owner_id == worker_id
#endif
	 ) {
      WRITE_UNLOCK(ae->ARWLock);
      return pe;
    }
    p0 = pe->NextOfPE;
  }
  new = (GlobalEntry *) Yap_AllocAtomSpace(sizeof(*new));
  INIT_RWLOCK(new->GRWLock);
  new->KindOfPE = GlobalProperty;
#if THREADS
  new->owner_id = worker_id;
#endif
  new->NextGE = LOCAL_GlobalVariables;
  LOCAL_GlobalVariables = new;
  new->AtomOfGE = ae;
  AddPropToAtom(ae, (PropEntry *)new);
  RESET_VARIABLE(&new->global);
  WRITE_UNLOCK(ae->ARWLock);
  return new;
}

static UInt
garena_overflow_size(CELL *arena USES_REGS)
{
  UInt dup = (((CELL *)arena-H0)*sizeof(CELL))>>3;
  if (dup < 64*1024*LOCAL_GlobalArenaOverflows)
    dup = 64*1024*LOCAL_GlobalArenaOverflows;
  if (dup > 1024*1024)
    return 1024*1024;
  return dup;
}

static Int
p_nb_setarg( USES_REGS1 )
{
  Term wheret = Deref(ARG1);
  Term dest;
  Term to;
  UInt arity, pos;
  CELL *destp;

  if (IsVarTerm(wheret)) {
    Yap_Error(INSTANTIATION_ERROR,wheret,"nb_setarg");
    return FALSE; 
  }
  if (!IsIntegerTerm(wheret)) {
    Yap_Error(TYPE_ERROR_INTEGER,wheret,"nb_setarg");
    return FALSE; 
  }
  pos = IntegerOfTerm(wheret);
  dest = Deref(ARG2);
  if (IsVarTerm(dest)) {
    Yap_Error(INSTANTIATION_ERROR,dest,"nb_setarg");
    return FALSE; 
  } else if (IsPrimitiveTerm(dest)) {
    arity = 0;
  } else if (IsPairTerm(dest)) {
    arity = 2;
  } else {
    arity = ArityOfFunctor(FunctorOfTerm(dest));
  }
  if (pos < 1 || pos > arity)
    return FALSE;

  to = Deref(ARG3);
  to = CopyTermToArena(ARG3, LOCAL_GlobalArena, FALSE, TRUE, 3, &LOCAL_GlobalArena, garena_overflow_size(ArenaPt(LOCAL_GlobalArena) PASS_REGS) PASS_REGS);
  if (to == 0L)
    return FALSE;

  dest = Deref(ARG2);
  if (IsPairTerm(dest)) {
    destp = RepPair(dest)-1;
  } else {
    destp = RepAppl(dest);
  }
  destp[pos] = to;
  return TRUE;
}

static Int
p_nb_set_shared_arg( USES_REGS1 )
{
  Term wheret = Deref(ARG1);
  Term dest = Deref(ARG2);
  Term to;
  UInt arity, pos;
  CELL *destp;

  if (IsVarTerm(wheret)) {
    Yap_Error(INSTANTIATION_ERROR,wheret,"nb_setarg");
    return FALSE; 
  }
  if (!IsIntegerTerm(wheret)) {
    Yap_Error(TYPE_ERROR_INTEGER,wheret,"nb_setarg");
    return FALSE; 
  }
  pos = IntegerOfTerm(wheret);
  if (IsVarTerm(dest)) {
    Yap_Error(INSTANTIATION_ERROR,dest,"nb_setarg");
    return FALSE; 
  } else if (IsPrimitiveTerm(dest)) {
    arity = 0;
  } else if (IsPairTerm(dest)) {
    arity = 2;
  } else {
    arity = ArityOfFunctor(FunctorOfTerm(dest));
  }
  if (pos < 1 || pos > arity)
    return FALSE;
  to = CopyTermToArena(ARG3, LOCAL_GlobalArena, TRUE, TRUE, 3, &LOCAL_GlobalArena, garena_overflow_size(ArenaPt(LOCAL_GlobalArena) PASS_REGS) PASS_REGS);
  if (to == 0L)
    return FALSE;
  if (IsPairTerm(dest)) {
    destp = RepPair(dest)-1;
  } else {
    destp = RepAppl(dest);
  }
  destp[pos] = to;
  return TRUE;
}

static Int
p_nb_linkarg( USES_REGS1 )
{
  Term wheret = Deref(ARG1);
  Term dest = Deref(ARG2);
  UInt arity, pos;
  CELL *destp;

  if (IsVarTerm(wheret)) {
    Yap_Error(INSTANTIATION_ERROR,wheret,"nb_setarg");
    return FALSE; 
  }
  if (!IsIntegerTerm(wheret)) {
    Yap_Error(TYPE_ERROR_INTEGER,wheret,"nb_setarg");
    return FALSE; 
  }
  pos = IntegerOfTerm(wheret);
  if (IsVarTerm(dest)) {
    Yap_Error(INSTANTIATION_ERROR,dest,"nb_setarg");
    return FALSE; 
  } else if (IsPrimitiveTerm(dest)) {
    arity = 0;
    destp = NULL;
  } else if (IsPairTerm(dest)) {
    arity = 2;
    destp = RepPair(dest)-1;
  } else {
    arity = ArityOfFunctor(FunctorOfTerm(dest));
    destp = RepAppl(dest);
  }
  if (pos < 1 || pos > arity)
    return FALSE;
  destp[pos] = Deref(ARG3);
  return TRUE;
}

static Int
p_nb_linkval( USES_REGS1 )
{
  Term t = Deref(ARG1), to;
  GlobalEntry *ge;
  if (IsVarTerm(t)) {
    Yap_Error(INSTANTIATION_ERROR,t,"nb_linkval");
    return (TermNil);
  } else if (!IsAtomTerm(t)) {
      Yap_Error(TYPE_ERROR_ATOM,t,"nb_linkval");
      return (FALSE);
  }
  ge = GetGlobalEntry(AtomOfTerm(t) PASS_REGS);
  to = Deref(ARG2);
  WRITE_LOCK(ge->GRWLock);
  ge->global=to;
  WRITE_UNLOCK(ge->GRWLock);
  return TRUE;
}



static Int
p_nb_create_accumulator( USES_REGS1 )
{
  Term t = Deref(ARG1), acct, to;
  CELL *destp;

  if (IsVarTerm(t)) {
    Yap_Error(INSTANTIATION_ERROR,t,"nb_create_accumulator");
    return FALSE; 
  }
  if (!IsIntegerTerm(t) && !IsBigIntTerm(t) && !IsFloatTerm(t)) {
    Yap_Error(TYPE_ERROR_NUMBER,t,"nb_create_accumulator");
    return FALSE; 
  }
  acct = Yap_MkApplTerm(FunctorGNumber,1,&t);
  if (!Yap_unify(ARG2, acct)) {
    return FALSE;
  }
  to = CopyTermToArena(t, LOCAL_GlobalArena, TRUE, TRUE, 2, &LOCAL_GlobalArena, garena_overflow_size(ArenaPt(LOCAL_GlobalArena) PASS_REGS) PASS_REGS);
  if (to == 0L)
    return FALSE;
  destp = RepAppl(Deref(ARG2));
  destp[1] = to;
  return TRUE;
}

static Int
p_nb_add_to_accumulator( USES_REGS1 )
{
  Term t = Deref(ARG1), t0, tadd;
  Functor f;
  CELL *destp;

  if (IsVarTerm(t)) {
    Yap_Error(INSTANTIATION_ERROR,t,"nb_create_accumulator");
    return FALSE; 
  }
  if (!IsApplTerm(t)) {
    Yap_Error(TYPE_ERROR_NUMBER,t,"nb_accumulator_value");
    return FALSE; 
  }
  f = FunctorOfTerm(t);
  if (f != FunctorGNumber) {
    return FALSE;
  }
  destp = RepAppl(t);
  t0 = Deref(destp[1]);
  tadd = Deref(ARG2);
  if (IsVarTerm(tadd)) {
    Yap_Error(INSTANTIATION_ERROR,tadd,"nb_create_accumulator");
    return FALSE; 
  }
  if (IsIntegerTerm(t0) && IsIntegerTerm(tadd)) {
    Int i0 = IntegerOfTerm(t0);
    Int i1 = IntegerOfTerm(tadd);
    Term new = MkIntegerTerm(i0+i1);

    if (IsIntTerm(new)) {
      /* forget it if it was something else */
      destp[1] = new;
    } else {
      /* long, do we have spapce or not ?? */
      if (IsLongIntTerm(t0)) {
	CELL *target = RepAppl(t0);
	CELL *source = RepAppl(new);
	target[1] = source[1];
      } else {
	/* we need to create a new long int */
	new = CopyTermToArena(new, LOCAL_GlobalArena, TRUE, TRUE, 2, &LOCAL_GlobalArena, garena_overflow_size(ArenaPt(LOCAL_GlobalArena) PASS_REGS) PASS_REGS);
	destp = RepAppl(Deref(ARG1));
	destp[1] = new;
      }
    }
    return TRUE;
  }
  if (IsFloatTerm(t0) && IsFloatTerm(tadd)) {
    Float f0 = FloatOfTerm(t0);
    Float f1 = FloatOfTerm(tadd);
    Term new = MkFloatTerm(f0+f1);
    CELL *target = RepAppl(t0);
    CELL *source = RepAppl(new);

#if  SIZEOF_DOUBLE == 2*SIZEOF_LONG_INT
    target[2] = source[2];
#endif
    target[1] = source[1];
    return TRUE;
  }
  if (IsNumTerm(t0) && IsNumTerm(tadd)) {
    Term t2[2], new;
    t2[0] = t0;
    t2[1] = tadd;
    new = Yap_MkApplTerm(FunctorPlus, 2, t2);

    new = Yap_Eval(new);
    new = CopyTermToArena(new, LOCAL_GlobalArena, TRUE, TRUE, 2, &LOCAL_GlobalArena, garena_overflow_size(ArenaPt(LOCAL_GlobalArena) PASS_REGS)  PASS_REGS);
    destp = RepAppl(Deref(ARG1));
    destp[1] = new;    

    return TRUE;
  }
  return FALSE;
}


static Int
p_nb_accumulator_value( USES_REGS1 )
{
  Term t = Deref(ARG1), to;
  Functor f;

  if (IsVarTerm(t)) {
    Yap_Error(INSTANTIATION_ERROR,t,"nb_accumulator_value");
    return FALSE; 
  }
  if (!IsApplTerm(t)) {
    Yap_Error(TYPE_ERROR_NUMBER,t,"nb_accumulator_value");
    return FALSE; 
  }
  f = FunctorOfTerm(t);
  if (f != FunctorGNumber) {
    return FALSE;
  }
  to = Yap_CopyTerm(RepAppl(t)[1]);
  return Yap_unify(to, ARG2);
}


Term
Yap_SetGlobalVal(Atom at, Term t0)
{
  CACHE_REGS
  Term to;
  GlobalEntry *ge;
  ge = GetGlobalEntry(at PASS_REGS);
  to = CopyTermToArena(t0, LOCAL_GlobalArena, FALSE, TRUE, 2, &LOCAL_GlobalArena, garena_overflow_size(ArenaPt(LOCAL_GlobalArena) PASS_REGS) PASS_REGS);
  if (to == 0L)
    return to;
  WRITE_LOCK(ge->GRWLock);
  ge->global=to;
  WRITE_UNLOCK(ge->GRWLock);
  return to;
}

Term
Yap_SaveTerm(Term t0)
{
  CACHE_REGS
  Term to;
  to = CopyTermToArena(t0, LOCAL_GlobalArena, FALSE, TRUE, 2, &LOCAL_GlobalArena, garena_overflow_size(ArenaPt(LOCAL_GlobalArena) PASS_REGS) PASS_REGS);
  if (to == 0L)
    return to;
  return to;
}

static Int
p_nb_setval( USES_REGS1 )
{
  Term t = Deref(ARG1);
  if (IsVarTerm(t)) {
    Yap_Error(INSTANTIATION_ERROR,t,"nb_setval");
    return (TermNil);
  } else if (!IsAtomTerm(t)) {
      Yap_Error(TYPE_ERROR_ATOM,t,"nb_setval");
      return (FALSE);
  }
  return Yap_SetGlobalVal(AtomOfTerm(t), ARG2);
}

static Int
p_nb_set_shared_val( USES_REGS1 )
{
  Term t = Deref(ARG1), to;
  GlobalEntry *ge;
  if (IsVarTerm(t)) {
    Yap_Error(INSTANTIATION_ERROR,t,"nb_setval");
    return (TermNil);
  } else if (!IsAtomTerm(t)) {
      Yap_Error(TYPE_ERROR_ATOM,t,"nb_setval");
      return (FALSE);
  }
  ge = GetGlobalEntry(AtomOfTerm(t) PASS_REGS);
  to = CopyTermToArena(ARG2, LOCAL_GlobalArena, TRUE, TRUE, 2, &LOCAL_GlobalArena, garena_overflow_size(ArenaPt(LOCAL_GlobalArena) PASS_REGS) PASS_REGS);
  if (to == 0L)
    return FALSE;
  WRITE_LOCK(ge->GRWLock);
  ge->global=to;
  WRITE_UNLOCK(ge->GRWLock);
  return TRUE;
}

static Int
p_b_setval( USES_REGS1 )
{
  Term t = Deref(ARG1);
  GlobalEntry *ge;

  if (IsVarTerm(t)) {
    Yap_Error(INSTANTIATION_ERROR,t,"b_setval");
    return (TermNil);
  } else if (!IsAtomTerm(t)) {
      Yap_Error(TYPE_ERROR_ATOM,t,"b_setval");
      return (FALSE);
  }
  ge = GetGlobalEntry(AtomOfTerm(t) PASS_REGS);
  WRITE_LOCK(ge->GRWLock);
#ifdef MULTI_ASSIGNMENT_VARIABLES
  /* the evil deed is to be done now */
  {
    /* but first make sure we are doing on a global object, or a constant! */
    Term t = Deref(ARG2);
    if (IsVarTerm(t) && VarOfTerm(t) > H && VarOfTerm(t) < LCL0) {
      Term tn = MkVarTerm();
      Bind_Local(VarOfTerm(t), tn);
      t = tn;
    }
    MaBind(&ge->global, t);
  }
  WRITE_UNLOCK(ge->GRWLock);
  return TRUE;
#else
  WRITE_UNLOCK(ge->GRWLock);
  Yap_Error(SYSTEM_ERROR,t,"update_array");
  return FALSE;
#endif
}

static Int
p_nb_getval( USES_REGS1 )
{
  Term t = Deref(ARG1), to;
  GlobalEntry *ge;

  if (IsVarTerm(t)) {
    Yap_Error(INSTANTIATION_ERROR,t,"nb_getval");
    return FALSE;
  } else if (!IsAtomTerm(t)) {
    Yap_Error(TYPE_ERROR_ATOM,t,"nb_getval");
    return FALSE;
  }
  ge = FindGlobalEntry(AtomOfTerm(t) PASS_REGS);
  if (!ge) {
    return Yap_unify(TermNil, ARG3);
  }
  READ_LOCK(ge->GRWLock);
  to = ge->global;
  if (IsVarTerm(to) && IsUnboundVar(VarOfTerm(to))) {
    Term t = MkVarTerm();
    Bind(VarOfTerm(to), t);
    to = t;
  }
  READ_UNLOCK(ge->GRWLock);
  if (to == TermFoundVar)
    return FALSE;
  return Yap_unify(ARG2, to);
}


static Int 
nbdelete(Atom at USES_REGS)
{
  GlobalEntry *ge, *g;
  AtomEntry *ae;
  Prop gp, g0;

  ge = FindGlobalEntry(at PASS_REGS);
  if (!ge) {
    Yap_Error(EXISTENCE_ERROR_VARIABLE,MkAtomTerm(at),"nb_delete");
    return FALSE;
  }
  WRITE_LOCK(ge->GRWLock);
  ae = ge->AtomOfGE;
  if (LOCAL_GlobalVariables == ge) {
    LOCAL_GlobalVariables = ge->NextGE;
  } else {
    g = LOCAL_GlobalVariables;
    while (g->NextGE != ge) 
      g = g->NextGE;
    g->NextGE = ge->NextGE;
  }
  gp = AbsGlobalProp(ge);
  WRITE_LOCK(ae->ARWLock);
  if (ae->PropsOfAE == gp) {
    ae->PropsOfAE = ge->NextOfPE;
  } else {
    g0 = ae->PropsOfAE;
    while (g0->NextOfPE != gp) 
      g0 = g0->NextOfPE;
    g0->NextOfPE = ge->NextOfPE;
  }
  WRITE_UNLOCK(ae->ARWLock);
  WRITE_UNLOCK(ge->GRWLock);
  Yap_FreeCodeSpace((char *)ge);
  return TRUE;
}

Int
Yap_DeleteGlobal(Atom at)
{
  CACHE_REGS
  return nbdelete(at PASS_REGS);
}

static Int
p_nb_delete( USES_REGS1 )
{
  Term t = Deref(ARG1);

  if (IsVarTerm(t)) {
    Yap_Error(INSTANTIATION_ERROR,t,"nb_delete");
    return FALSE;
  } else if (!IsAtomTerm(t)) {
    Yap_Error(TYPE_ERROR_ATOM,t,"nb_delete");
    return FALSE;
  }
  return nbdelete(AtomOfTerm(t) PASS_REGS);
}

static Int
p_nb_create( USES_REGS1 )
{
  Term t = Deref(ARG1);
  Term tname = Deref(ARG2);
  Term tarity = Deref(ARG3);
  Term to;
  GlobalEntry *ge;

  if (IsVarTerm(t)) {
    Yap_Error(INSTANTIATION_ERROR,t,"nb_create");
    return FALSE;
  } else if (!IsAtomTerm(t)) {
    Yap_Error(TYPE_ERROR_ATOM,t,"nb_create");
    return FALSE;
  }
  ge = GetGlobalEntry(AtomOfTerm(t) PASS_REGS);
  if (!ge) {
    Yap_Error(EXISTENCE_ERROR_VARIABLE,t,"nb_create");
    return FALSE;
  }
  if (IsVarTerm(tarity)) {
    Yap_Error(INSTANTIATION_ERROR,tarity,"nb_create");
    return FALSE;
  } else if (!IsIntegerTerm(tarity)) {
    Yap_Error(TYPE_ERROR_INTEGER,tarity,"nb_create");
    return FALSE;
  }
  if (IsVarTerm(tname)) {
    Yap_Error(INSTANTIATION_ERROR,tname,"nb_create");
    return FALSE;
  } else if (!IsAtomTerm(tname)) {
    Yap_Error(TYPE_ERROR_ATOM,tname,"nb_create");
    return FALSE;
  }
  to = CreateTermInArena(LOCAL_GlobalArena, AtomOfTerm(tname), IntegerOfTerm(tarity),  3, &LOCAL_GlobalArena, 0L PASS_REGS);
  if (!to)
    return FALSE;
  WRITE_LOCK(ge->GRWLock);
  ge->global=to;
  WRITE_UNLOCK(ge->GRWLock);
  return TRUE;
}

static Int
p_nb_create2( USES_REGS1 )
{
  Term t = Deref(ARG1);
  Term tname = Deref(ARG2);
  Term tarity = Deref(ARG3);
  Term tinit = Deref(ARG4);
  Term to;
  GlobalEntry *ge;

  if (IsVarTerm(t)) {
    Yap_Error(INSTANTIATION_ERROR,t,"nb_create");
    return FALSE;
  } else if (!IsAtomTerm(t)) {
    Yap_Error(TYPE_ERROR_ATOM,t,"nb_create");
    return FALSE;
  }
  ge = GetGlobalEntry(AtomOfTerm(t) PASS_REGS);
  if (!ge) {
    Yap_Error(EXISTENCE_ERROR_VARIABLE,t,"nb_create");
    return FALSE;
  }
  if (IsVarTerm(tarity)) {
    Yap_Error(INSTANTIATION_ERROR,tarity,"nb_create");
    return FALSE;
  } else if (!IsIntegerTerm(tarity)) {
    Yap_Error(TYPE_ERROR_INTEGER,tarity,"nb_create");
    return FALSE;
  }
  if (IsVarTerm(tname)) {
    Yap_Error(INSTANTIATION_ERROR,tname,"nb_create");
    return FALSE;
  } else if (!IsAtomTerm(tname)) {
    Yap_Error(TYPE_ERROR_ATOM,tname,"nb_create");
    return FALSE;
  }
  if (IsVarTerm(tinit)) {
    Yap_Error(INSTANTIATION_ERROR,tname,"nb_create");
    return FALSE;
  } else if (!IsAtomTerm(tinit)) {
    Yap_Error(TYPE_ERROR_ATOM,tname,"nb_create");
    return FALSE;
  }
  to = CreateTermInArena(LOCAL_GlobalArena, AtomOfTerm(tname), IntegerOfTerm(tarity), 4, &LOCAL_GlobalArena, tinit PASS_REGS);
  if (!to)
    return FALSE;
  WRITE_LOCK(ge->GRWLock);
  ge->global=to;
  WRITE_UNLOCK(ge->GRWLock);
  return TRUE;
}

/* a non-backtrackable queue is a term of the form $array(Arena,Start,End,Size) plus an Arena. */

static Int 
nb_queue(UInt arena_sz USES_REGS)
{
  Term queue_arena, queue, ar[QUEUE_FUNCTOR_ARITY], *nar;
  Term t = Deref(ARG1);

  LOCAL_DepthArenas++;
  if (!IsVarTerm(t)) {
    if (!IsApplTerm(t)) {
      return FALSE;
    }
    return (FunctorOfTerm(t) == FunctorNBQueue);
  }
  ar[QUEUE_ARENA] = 
    ar[QUEUE_HEAD] =
    ar[QUEUE_TAIL] =
    ar[QUEUE_SIZE] =
    MkIntTerm(0);
  queue = Yap_MkApplTerm(FunctorNBQueue,QUEUE_FUNCTOR_ARITY,ar);
  if (!Yap_unify(queue,ARG1))
    return FALSE;
  if (arena_sz < 4*1024)
    arena_sz = 4*1024;
  queue_arena = NewArena(arena_sz, 1, NULL PASS_REGS);
  if (queue_arena == 0L) {
    return FALSE;
  }
  nar = RepAppl(Deref(ARG1))+1;
  nar[QUEUE_ARENA] = queue_arena;
  return TRUE;
}

static Int
p_nb_queue( USES_REGS1 )
{
  UInt arena_sz = (ASP-H)/16;
  if (LOCAL_DepthArenas > 1)
    arena_sz /= LOCAL_DepthArenas;
  if (arena_sz < MIN_ARENA_SIZE)
    arena_sz = MIN_ARENA_SIZE;
  if (arena_sz > MAX_ARENA_SIZE)
    arena_sz = MAX_ARENA_SIZE;
  return nb_queue(arena_sz PASS_REGS);
}

static Int
p_nb_queue_sized( USES_REGS1 )
{
  Term t = Deref(ARG2);
  if (IsVarTerm(t)) {
    Yap_Error(INSTANTIATION_ERROR,t,"nb_queue");
    return FALSE;
  }
  if (!IsIntegerTerm(t)) {
      Yap_Error(TYPE_ERROR_INTEGER,t,"nb_queue");
      return FALSE;
  }
  return nb_queue((UInt)IntegerOfTerm(t) PASS_REGS);
}

static CELL *
GetQueue(Term t, char* caller)
{
  t = Deref(t);

  if (IsVarTerm(t)) {
    Yap_Error(INSTANTIATION_ERROR,t,caller);
    return NULL;
  } 
  if (!IsApplTerm(t)) {
      Yap_Error(TYPE_ERROR_COMPOUND,t,caller);
      return NULL;
  }
  if (FunctorOfTerm(t) != FunctorNBQueue) {
      Yap_Error(DOMAIN_ERROR_ARRAY_TYPE,t,caller);
      return NULL;
  }
  return RepAppl(t)+1;
}

static Term
GetQueueArena(CELL *qd, char* caller)
{
  Term t = Deref(qd[QUEUE_ARENA]);

  if (IsVarTerm(t)) {
    Yap_Error(INSTANTIATION_ERROR,t,caller);
    return 0L;
  } 
  if (!IsApplTerm(t)) {
      Yap_Error(TYPE_ERROR_COMPOUND,t,caller);
      return 0L;
  }
  if (FunctorOfTerm(t) != FunctorBigInt) {
      Yap_Error(DOMAIN_ERROR_ARRAY_TYPE,t,caller);
      return 0L;
  }
  return t;
}

static void
RecoverArena(Term arena USES_REGS)
{
  CELL *pt = ArenaPt(arena),
    *max = ArenaLimit(arena);
  
  if (max == H) {
    H = pt;
  }
}

static Int
p_nb_queue_close( USES_REGS1 )
{
  Term t = Deref(ARG1);
  Int out;

  LOCAL_DepthArenas--;
  if (!IsVarTerm(t)) {
    CELL *qp;

    qp = GetQueue(t, "queue/3");
    if (qp == NULL) {
      return
	Yap_unify(ARG3, ARG2);
    }
    if (qp[QUEUE_ARENA] != MkIntTerm(0))
      RecoverArena(qp[QUEUE_ARENA] PASS_REGS);
    if (qp[QUEUE_SIZE] == MkIntTerm(0)) {
      return 
	Yap_unify(ARG3, ARG2);
    }
    out = 
      Yap_unify(ARG3, qp[QUEUE_TAIL]) &&
      Yap_unify(ARG2, qp[QUEUE_HEAD]);
    qp[-1] = (CELL)Yap_MkFunctor(AtomHeap,1);
    qp[QUEUE_ARENA] =
    qp[QUEUE_HEAD] = 
    qp[QUEUE_TAIL] = MkIntegerTerm(0);
    return out;
  }
  Yap_Error(INSTANTIATION_ERROR,t,"queue/3");
  return FALSE;
}

static Int
p_nb_queue_enqueue( USES_REGS1 )
{
  CELL *qd = GetQueue(ARG1,"enqueue"), *oldH, *oldHB;
  UInt old_sz;
  Term arena, qsize, to;
  UInt min_size;

  if (!qd)
    return FALSE;
  arena = GetQueueArena(qd,"enqueue");
  if (arena == 0L)
    return FALSE;
  if (IsPairTerm(qd[QUEUE_HEAD])) {
    min_size = ArenaPt(arena)-RepPair(qd[QUEUE_HEAD]);
  } else {
    min_size = 0L;
  }
  to = CopyTermToArena(ARG2, arena, FALSE, TRUE, 2, qd+QUEUE_ARENA, min_size PASS_REGS);
  if (to == 0L)
    return FALSE;
  qd = GetQueue(ARG1,"enqueue");
  arena = GetQueueArena(qd,"enqueue");
  /* garbage collection ? */
  oldH = H;
  oldHB = HB;
  H = HB = ArenaPt(arena);
  old_sz = ArenaSz(arena);
  qsize = IntegerOfTerm(qd[QUEUE_SIZE]);
  while (old_sz < MIN_ARENA_SIZE) {
    UInt gsiz = H-RepPair(qd[QUEUE_HEAD]);
    H = oldH;
    HB = oldHB;
    if (gsiz > 1024*1024) {
      gsiz = 1024*1024;
    } else if (gsiz < 1024) {
      gsiz = 1024;
    }
    ARG3 = to;
    /*    fprintf(stderr,"growing %ld cells\n",(unsigned long int)gsiz);*/
    if (!GrowArena(arena, ArenaLimit(arena), old_sz, gsiz, 3 PASS_REGS)) {
      Yap_Error(OUT_OF_STACK_ERROR, arena, LOCAL_ErrorMessage);
      return 0L;
    }    
    to = ARG3;
    qd = RepAppl(Deref(ARG1))+1;
    arena = GetQueueArena(qd,"enqueue");
    oldH = H;
    oldHB = HB;
    H = HB = ArenaPt(arena);
    old_sz = ArenaSz(arena);    
  }
  qd[QUEUE_SIZE] = Global_MkIntegerTerm(qsize+1);
  if (qsize == 0) {
    qd[QUEUE_HEAD] = AbsPair(H);
  } else {
    *VarOfTerm(qd[QUEUE_TAIL]) = AbsPair(H);
  }
  *H++ = to;
  RESET_VARIABLE(H);
  qd[QUEUE_TAIL] = (CELL)H;
  H++;
  CloseArena(oldH, oldHB, ASP, qd+QUEUE_ARENA, old_sz PASS_REGS);
  return TRUE;
}

static Int
p_nb_queue_dequeue( USES_REGS1 )
{
  CELL *qd = GetQueue(ARG1,"dequeue");
  UInt old_sz, qsz;
  Term arena, out;
  CELL *oldH, *oldHB;

  if (!qd)
    return FALSE;
  qsz = IntegerOfTerm(qd[QUEUE_SIZE]);
  if (qsz == 0)
    return FALSE;
  arena = GetQueueArena(qd,"dequeue");
  if (arena == 0L)
    return FALSE;
  old_sz = ArenaSz(arena);
  out = HeadOfTerm(qd[QUEUE_HEAD]);
  qd[QUEUE_HEAD] = TailOfTerm(qd[QUEUE_HEAD]);
  /* garbage collection ? */
  oldH = H;
  oldHB = HB;
  qd[QUEUE_SIZE] = Global_MkIntegerTerm(qsz-1);
  CloseArena(oldH, oldHB, ASP, &arena, old_sz PASS_REGS);
  return Yap_unify(out, ARG2);
}

/* purge an entry from the queue, replacing it by [] */
static Int
p_nb_queue_replace( USES_REGS1 )
{
  CELL *qd = GetQueue(ARG1,"dequeue");
  UInt qsz;
  Term queue, t = Deref(ARG2);

  if (!qd)
    return FALSE;
  qsz = IntegerOfTerm(qd[QUEUE_SIZE]);
  if (qsz == 0)
    return FALSE;
  
  queue = qd[QUEUE_HEAD];
  for (; qsz > 0; qsz--) {
    if (Yap_eq(HeadOfTerm(queue), t)) {
      *RepPair(Deref(queue)) = Deref(ARG3);
      return TRUE;
    }
    queue = TailOfTerm(queue);
  }
  return FALSE;
}

static Int
p_nb_queue_peek( USES_REGS1 )
{
  CELL *qd = GetQueue(ARG1,"queue_peek");
  UInt qsz;

  if (!qd)
    return FALSE;
  qsz = IntegerOfTerm(qd[QUEUE_SIZE]);
  if (qsz == 0)
    return FALSE;
  return Yap_unify(HeadOfTerm(qd[QUEUE_HEAD]), ARG2);
}

static Int
p_nb_queue_empty( USES_REGS1 )
{
  CELL *qd = GetQueue(ARG1,"queue_empty");

  if (!qd)
    return FALSE;
  return (IntegerOfTerm(qd[QUEUE_SIZE]) == 0);
}

static Int
p_nb_queue_size( USES_REGS1 )
{
  CELL *qd = GetQueue(ARG1,"queue_size");

  if (!qd)
    return FALSE;
  return Yap_unify(ARG2,qd[QUEUE_SIZE]);
}

static Int
p_nb_queue_show( USES_REGS1 )
{
  CELL *qd = GetQueue(ARG1,"queue_size");

  if (!qd)
    return FALSE;
  return Yap_unify(ARG2,qd[QUEUE_HEAD]);
}


static CELL *
GetHeap(Term t, char* caller)
{
  t = Deref(t);

  if (IsVarTerm(t)) {
    Yap_Error(INSTANTIATION_ERROR,t,caller);
    return NULL;
  } 
  if (!IsApplTerm(t)) {
      Yap_Error(TYPE_ERROR_COMPOUND,t,caller);
      return NULL;
  }
  return RepAppl(t)+1;
}

static Term
MkZeroApplTerm(Functor f, UInt sz USES_REGS)
{
  Term t0, tf;
  CELL *pt;

  if (H+(sz+1) > ASP-1024)
    return TermNil;
  tf = AbsAppl(H);
  *H = (CELL)f;
  t0 = MkIntTerm(0);
  pt = H+1;
  while (sz--) {
    *pt++ = t0;
  }
  H = pt;
  return tf;
}

static Int
p_nb_heap( USES_REGS1 )
{
  Term heap_arena, heap, *ar, *nar;
  UInt hsize;
  Term tsize = Deref(ARG1);
  UInt arena_sz = (H-H0)/16;

  if (IsVarTerm(tsize)) {
    Yap_Error(INSTANTIATION_ERROR,tsize,"nb_heap");
    return FALSE;
  } else {
    if (!IsIntegerTerm(tsize)) {
      Yap_Error(TYPE_ERROR_INTEGER,tsize,"nb_heap");
      return FALSE;
    }
    hsize = IntegerOfTerm(tsize);
  }

  while ((heap = MkZeroApplTerm(Yap_MkFunctor(AtomHeap,2*hsize+HEAP_START+1),2*hsize+HEAP_START+1 PASS_REGS)) == TermNil) {
    if (!Yap_gcl((2*hsize+HEAP_START+1)*sizeof(CELL), 2, ENV, P)) {
      Yap_Error(OUT_OF_STACK_ERROR, TermNil, LOCAL_ErrorMessage);
      return FALSE;
    }
  }
  if (!Yap_unify(heap,ARG2))
    return FALSE;
  ar = RepAppl(heap)+1;
  ar[HEAP_ARENA] = 
    ar[HEAP_SIZE] = 
    MkIntTerm(0);
  ar[HEAP_MAX] = tsize;
  if (arena_sz < 1024)
    arena_sz = 1024;
  heap_arena = NewArena(arena_sz,1,NULL PASS_REGS);
  if (heap_arena == 0L) {
    return FALSE;
  }
  nar = RepAppl(Deref(ARG2))+1;
  nar[HEAP_ARENA] = heap_arena;
  return TRUE;
}

static Int
p_nb_heap_close( USES_REGS1 )
{
  Term t = Deref(ARG1);
  if (!IsVarTerm(t)) {
    CELL *qp;

    qp = RepAppl(t)+1;
    if (qp[HEAP_ARENA] != MkIntTerm(0))
      RecoverArena(qp[HEAP_ARENA] PASS_REGS);
    qp[-1] = (CELL)Yap_MkFunctor(AtomHeap,1);
    qp[0] = MkIntegerTerm(0);
    return TRUE;
  }
  Yap_Error(INSTANTIATION_ERROR,t,"heap_close/1");
  return FALSE;
}

static void
PushHeap(CELL *pt, UInt off)
{
  while (off) {
    UInt noff = (off+1)/2-1;
    if (Yap_compare_terms(pt[2*off], pt[2*noff]) < 0) {
      Term tk = pt[2*noff];
      Term tv = pt[2*noff+1];
      pt[2*noff] = pt[2*off];
      pt[2*noff+1] = pt[2*off+1];
      pt[2*off] = tk;
      pt[2*off+1] = tv;
      off = noff;
    } else {
      return;
    }
  }
}

static void
DelHeapRoot(CELL *pt, UInt sz)
{
  UInt indx = 0;
  Term tk, tv;

  sz--;
  tk = pt[2*sz];
  tv = pt[2*sz+1];
  pt[2*sz] = TermNil;
  pt[2*sz+1] = TermNil;
  while (TRUE) {
    if (sz < 2*indx+3 || Yap_compare_terms(pt[4*indx+2],pt[4*indx+4]) < 0) {
      if (sz < 2*indx+2 || Yap_compare_terms(tk, pt[4*indx+2]) < 0) {
	pt[2*indx] = tk;
	pt[2*indx+1] = tv;
	return;
      } else {
	pt[2*indx] = pt[4*indx+2];
	pt[2*indx+1] = pt[4*indx+3];
	indx = 2*indx+1;
      }
    } else {
      if (Yap_compare_terms(tk, pt[4*indx+4]) < 0) {
	pt[2*indx] = tk;
	pt[2*indx+1] = tv;
	return;
      } else {
	pt[2*indx] = pt[4*indx+4];
	pt[2*indx+1] = pt[4*indx+5];
	indx = 2*indx+2;
      }
    }
  }
}

static Int
p_nb_heap_add_to_heap( USES_REGS1 )
{
  CELL *qd = GetHeap(ARG1,"add_to_heap"), *oldH, *oldHB, *pt;
  UInt hsize, hmsize, old_sz;
  Term arena, to, key;
  UInt mingrow;

  if (!qd)
    return FALSE;
 restart:
  hsize = IntegerOfTerm(qd[HEAP_SIZE]);
  hmsize = IntegerOfTerm(qd[HEAP_MAX]);
  if (hsize == hmsize) {
    CELL *top = qd+(HEAP_START+2*hmsize);
    UInt extra_size;

    if (hmsize <= 64*1024) {
      extra_size = 64*1024;
    } else {
      extra_size = hmsize;
    }
    if ((extra_size=Yap_InsertInGlobal(top, extra_size*2*sizeof(CELL)))==0) {
      Yap_Error(OUT_OF_STACK_ERROR,TermNil,"No Stack Space for Non-Backtrackable terms");
      return FALSE;
    }
    extra_size = extra_size/(2*sizeof(CELL));
    qd = GetHeap(ARG1,"add_to_heap");
    hmsize += extra_size;
    if (!qd)
      return FALSE;
    qd[-1] = (CELL)Yap_MkFunctor(AtomHeap,2*hmsize+HEAP_START);
    top = qd+(HEAP_START+2*(hmsize-extra_size));
    while (extra_size) {
      RESET_VARIABLE(top);
      RESET_VARIABLE(top+1);
      top+=2;
      extra_size--;
    }
    arena = qd[HEAP_ARENA];
    old_sz = ArenaSz(arena);
    oldH = H;
    oldHB = HB;
    H = HB = ArenaPt(arena);
    qd[HEAP_MAX] = Global_MkIntegerTerm(hmsize);
    CloseArena(oldH, oldHB, ASP, qd+HEAP_ARENA, old_sz PASS_REGS);
    goto restart;
  }
  arena = qd[HEAP_ARENA];
  if (arena == 0L)
    return FALSE;
  mingrow = garena_overflow_size(ArenaPt(arena) PASS_REGS);
  ARG2 = CopyTermToArena(ARG2, arena, FALSE, TRUE, 3, qd+HEAP_ARENA, mingrow PASS_REGS);
  qd = GetHeap(ARG1,"add_to_heap");
  arena = qd[HEAP_ARENA];
  to = CopyTermToArena(ARG3, arena, FALSE, TRUE, 3, qd+HEAP_ARENA, mingrow PASS_REGS);
  /* protect key in ARG2 in case there is an overflow while copying to */
  key = ARG2;
  if (key == 0 || to == 0L)
    return FALSE;
  qd = GetHeap(ARG1,"add_to_heap");
  arena = qd[HEAP_ARENA];
  /* garbage collection ? */
  oldH = H;
  oldHB = HB;
  H = HB = ArenaPt(arena);
  old_sz = ArenaSz(arena);
  while (old_sz < MIN_ARENA_SIZE) {
    UInt gsiz = hsize*2;

    H = oldH;
    HB = oldHB;
    if (gsiz > 1024*1024) {
      gsiz = 1024*1024;
    } else if (gsiz < 1024) {
      gsiz = 1024;
    }
    ARG3 = to;
    if (!GrowArena(arena, ArenaLimit(arena), old_sz, gsiz, 3 PASS_REGS)) {
      Yap_Error(OUT_OF_STACK_ERROR, arena, LOCAL_ErrorMessage);
      return 0L;
    }    
    to = ARG3;
    qd = RepAppl(Deref(ARG1))+1;
    arena = qd[HEAP_ARENA];
    oldH = H;
    oldHB = HB;
    H = HB = ArenaPt(arena);
    old_sz = ArenaSz(arena);    
  }
  pt = qd+HEAP_START;
  pt[2*hsize] = key;
  pt[2*hsize+1] = to;
  PushHeap(pt, hsize);
  qd[HEAP_SIZE] = Global_MkIntegerTerm(hsize+1);
  CloseArena(oldH, oldHB, ASP, qd+HEAP_ARENA, old_sz PASS_REGS);
  return TRUE;
}

static Int
p_nb_heap_del( USES_REGS1 )
{
  CELL *qd = GetHeap(ARG1,"deheap");
  UInt old_sz, qsz;
  Term arena;
  CELL *oldH, *oldHB;
  Term tk, tv;

  if (!qd)
    return FALSE;
  qsz = IntegerOfTerm(qd[HEAP_SIZE]);
  if (qsz == 0)
    return FALSE;
  arena = qd[HEAP_ARENA];
  if (arena == 0L)
    return FALSE;
  old_sz = ArenaSz(arena);
  /* garbage collection ? */
  oldH = H;
  oldHB = HB;
  qd[HEAP_SIZE] = Global_MkIntegerTerm(qsz-1);
  CloseArena(oldH, oldHB, ASP, &arena, old_sz PASS_REGS);
  tk = qd[HEAP_START];
  tv = qd[HEAP_START+1];
  DelHeapRoot(qd+HEAP_START, qsz);
  return Yap_unify(tk, ARG2) &&
    Yap_unify(tv, ARG3);
}

static Int
p_nb_heap_peek( USES_REGS1 )
{
  CELL *qd = GetHeap(ARG1,"heap_peek");
  UInt qsz;
  Term tk, tv;

  if (!qd)
    return FALSE;
  qsz = IntegerOfTerm(qd[HEAP_SIZE]);
  if (qsz == 0)
    return FALSE;
  tk = qd[HEAP_START];
  tv = qd[HEAP_START+1];
  return Yap_unify(tk, ARG2) &&
    Yap_unify(tv, ARG3);
}

static Int
p_nb_heap_empty( USES_REGS1 )
{
  CELL *qd = GetHeap(ARG1,"heap_empty");

  if (!qd)
    return FALSE;
  return (IntegerOfTerm(qd[HEAP_SIZE]) == 0);
}

static Int
p_nb_heap_size( USES_REGS1 )
{
  CELL *qd = GetHeap(ARG1,"heap_size");

  if (!qd)
    return FALSE;
  return Yap_unify(ARG2,qd[HEAP_SIZE]);
}

static Int
p_nb_beam( USES_REGS1 )
{
  Term beam_arena, beam, *ar, *nar;
  UInt hsize;
  Term tsize = Deref(ARG1);
  UInt arena_sz = (H-H0)/16;

  if (IsVarTerm(tsize)) {
    Yap_Error(INSTANTIATION_ERROR,tsize,"nb_beam");
    return FALSE;
  } else {
    if (!IsIntegerTerm(tsize)) {
      Yap_Error(TYPE_ERROR_INTEGER,tsize,"nb_beam");
      return FALSE;
    }
    hsize = IntegerOfTerm(tsize);
  }
  while ((beam = MkZeroApplTerm(Yap_MkFunctor(AtomHeap,5*hsize+HEAP_START+1),5*hsize+HEAP_START+1 PASS_REGS)) == TermNil) {
    if (!Yap_gcl((4*hsize+HEAP_START+1)*sizeof(CELL), 2, ENV, P)) {
      Yap_Error(OUT_OF_STACK_ERROR, TermNil, LOCAL_ErrorMessage);
      return FALSE;
    }
  }
  if (!Yap_unify(beam,ARG2))
    return FALSE;
  ar = RepAppl(beam)+1;
  ar[HEAP_ARENA] = 
    ar[HEAP_SIZE] = 
    MkIntTerm(0);
  ar[HEAP_MAX] = tsize;
  if (arena_sz < 1024)
    arena_sz = 1024;
  beam_arena = NewArena(arena_sz,1,NULL PASS_REGS);
  if (beam_arena == 0L) {
    return FALSE;
  }
  nar = RepAppl(Deref(ARG2))+1;
  nar[HEAP_ARENA] = beam_arena;
  return TRUE;
}

static Int
p_nb_beam_close( USES_REGS1 )
{
  return p_nb_heap_close( PASS_REGS1 );
}


/* we have two queues, one with
   Key, IndxQueue2
   the other with
   Key, IndxQueue1, Val
*/
static void
PushBeam(CELL *pt, CELL *npt, UInt hsize, Term key, Term to)
{
  UInt off = hsize, off2 = hsize;
  Term toff, toff2;

  /* push into first queue */
  while (off) {
    UInt noff = (off+1)/2-1;
    if (Yap_compare_terms(key, pt[2*noff]) < 0) {
      UInt i2 = IntegerOfTerm(pt[2*noff+1]);

      pt[2*off] = pt[2*noff];
      pt[2*off+1] = pt[2*noff+1];
      npt[3*i2+1] = Global_MkIntegerTerm(off);
      off = noff;
    } else {
      break;
    }
  }
  toff = Global_MkIntegerTerm(off);
  /* off says where we are in first queue */
  /* push into second queue */
  while (off2) {
    UInt noff = (off2+1)/2-1;
    if (Yap_compare_terms(key, npt[3*noff]) > 0) {
      UInt i1 = IntegerOfTerm(npt[3*noff+1]);

      npt[3*off2] = npt[3*noff];
      npt[3*off2+1] = npt[3*noff+1];
      npt[3*off2+2] = npt[3*noff+2];
      pt[2*i1+1] = Global_MkIntegerTerm(off2);
      off2 = noff;
    } else {
      break;
    }
  }
  toff2 = Global_MkIntegerTerm(off2);
  /* store elements in their rightful place */
  npt[3*off2] = pt[2*off] = key;
  pt[2*off+1] = toff2;
  npt[3*off2+1] = toff;
  npt[3*off2+2] = to;
}

static void
DelBeamMax(CELL *pt, CELL *pt2, UInt sz)
{
  UInt off = IntegerOfTerm(pt2[1]);
  UInt indx = 0;
  Term tk, ti, tv;

  sz--;
  /* first, fix the reverse queue */
  tk = pt2[3*sz];
  ti = pt2[3*sz+1];
  tv = pt2[3*sz+2];
  while (TRUE) {
    if (sz < 2*indx+3 || Yap_compare_terms(pt2[6*indx+3],pt2[6*indx+6]) > 0) {
      if (sz < 2*indx+2 || Yap_compare_terms(tk, pt2[6*indx+3]) > 0) {
	break;
      } else {
	UInt off = IntegerOfTerm(pt2[6*indx+4]);

	pt2[3*indx] = pt2[6*indx+3];
	pt2[3*indx+1] = pt2[6*indx+4];
	pt2[3*indx+2] = pt2[6*indx+5];
	pt[2*off+1] = Global_MkIntegerTerm(indx);
	indx = 2*indx+1;
      }
    } else {
      if (Yap_compare_terms(tk, pt2[6*indx+6]) > 0) {
	break;
      } else {
	UInt off = IntegerOfTerm(pt2[6*indx+7]);

	pt2[3*indx] = pt2[6*indx+6];
	pt2[3*indx+1] = pt2[6*indx+7];
	pt2[3*indx+2] = pt2[6*indx+8];
	pt[2*off+1] = Global_MkIntegerTerm(indx);
	indx = 2*indx+2;
      }
    }
  }
  pt[2*IntegerOfTerm(ti)+1] = Global_MkIntegerTerm(indx);
  pt2[3*indx] = tk;
  pt2[3*indx+1] = ti;
  pt2[3*indx+2] = tv;
  /* now, fix the standard queue */
  if (off != sz) {
    Term toff, toff2, key;
    UInt off2;

    key = pt[2*sz];
    toff2 = pt[2*sz+1];
    off2 = IntegerOfTerm(toff2);
    /* off says where we are in first queue */
    /* push into second queue */
    while (off) {
      UInt noff = (off+1)/2-1;
      if (Yap_compare_terms(key, pt[2*noff]) < 0) {
	UInt i1 = IntegerOfTerm(pt[2*noff+1]);

	pt[2*off] = pt[2*noff];
	pt[2*off+1] = pt[2*noff+1];
	pt2[3*i1+1] = Global_MkIntegerTerm(off);
	off = noff;
      } else {
	break;
      }
    }
    toff = Global_MkIntegerTerm(off);
    /* store elements in their rightful place */
    pt[2*off] = key;
    pt2[3*off2+1] = toff;
    pt[2*off+1] = toff2;
  }
}

static Term
DelBeamMin(CELL *pt, CELL *pt2, UInt sz)
{
  UInt off2 = IntegerOfTerm(pt[1]);
  Term ov = pt2[3*off2+2]; /* return value */
  UInt indx = 0;
  Term tk, tv;

  sz--;
  /* first, fix the standard queue */
  tk = pt[2*sz];
  tv = pt[2*sz+1];
  while (TRUE) {
    if (sz < 2*indx+3 || Yap_compare_terms(pt[4*indx+2],pt[4*indx+4]) < 0) {
      if (sz < 2*indx+2 || Yap_compare_terms(tk, pt[4*indx+2]) < 0) {
	break;
      } else {
	UInt off2 = IntegerOfTerm(pt[4*indx+3]);
	pt[2*indx] = pt[4*indx+2];
	pt[2*indx+1] = pt[4*indx+3];
	pt2[3*off2+1] = Global_MkIntegerTerm(indx);
	indx = 2*indx+1;
      }
    } else {
      if (Yap_compare_terms(tk, pt[4*indx+4]) < 0) {
	break;
      } else {
	UInt off2 = IntegerOfTerm(pt[4*indx+5]);

	pt[2*indx] = pt[4*indx+4];
	pt[2*indx+1] = pt[4*indx+5];
	pt2[3*off2+1] = Global_MkIntegerTerm(indx);
	indx = 2*indx+2;
      }
    }
  }
  pt[2*indx] = tk;
  pt[2*indx+1] = tv;
  pt2[3*IntegerOfTerm(tv)+1] = Global_MkIntegerTerm(indx);
  /* now, fix the reverse queue */
  if (off2 != sz) {
    Term to, toff, toff2, key;
    UInt off;

    key = pt2[3*sz];
    toff = pt2[3*sz+1];
    to = pt2[3*sz+2];
    off = IntegerOfTerm(toff);
    /* off says where we are in first queue */
    /* push into second queue */
    while (off2) {
      UInt noff = (off2+1)/2-1;
      if (Yap_compare_terms(key, pt2[3*noff]) > 0) {
	UInt i1 = IntegerOfTerm(pt2[3*noff+1]);

	pt2[3*off2] = pt2[3*noff];
	pt2[3*off2+1] = pt2[3*noff+1];
	pt2[3*off2+2] = pt2[3*noff+2];
	pt[2*i1+1] = Global_MkIntegerTerm(off2);
	off2 = noff;
      } else {
	break;
      }
    }
    toff2 = Global_MkIntegerTerm(off2);
    /* store elements in their rightful place */
    pt2[3*off2] = key;
    pt[2*off+1] = toff2;
    pt2[3*off2+1] = toff;
    pt2[3*off2+2] = to;
  }
  return ov;
}

static Int
p_nb_beam_add_to_beam( USES_REGS1 )
{
  CELL *qd = GetHeap(ARG1,"add_to_beam"), *oldH, *oldHB, *pt;
  UInt hsize, hmsize, old_sz;
  Term arena, to, key;
  UInt mingrow;

  if (!qd)
    return FALSE;
  hsize = IntegerOfTerm(qd[HEAP_SIZE]);
  hmsize = IntegerOfTerm(qd[HEAP_MAX]);
  key = Deref(ARG2);
  if (hsize == hmsize) {
    pt = qd+HEAP_START;
    if (Yap_compare_terms(pt[2*hmsize],Deref(ARG2)) > 0) {
      /* smaller than current max, we need to drop current max */
      DelBeamMax(pt, pt+2*hmsize, hmsize);
      hsize--;
    } else {
      return TRUE;
    }
  }
  arena = qd[HEAP_ARENA];
  if (arena == 0L)
    return FALSE;
  mingrow = garena_overflow_size(ArenaPt(arena) PASS_REGS);
  key = CopyTermToArena(ARG2, qd[HEAP_ARENA], FALSE, TRUE, 3, qd+HEAP_ARENA, mingrow PASS_REGS);
  arena = qd[HEAP_ARENA];
  to = CopyTermToArena(ARG3, arena, FALSE, TRUE, 3, qd+HEAP_ARENA, mingrow PASS_REGS);
  if (key == 0 || to == 0L)
    return FALSE;
  qd = GetHeap(ARG1,"add_to_beam");
  arena = qd[HEAP_ARENA];
  /* garbage collection ? */
  oldH = H;
  oldHB = HB;
  H = HB = ArenaPt(arena);
  old_sz = ArenaSz(arena);
  while (old_sz < MIN_ARENA_SIZE) {
    UInt gsiz = hsize*2;

    H = oldH;
    HB = oldHB;
    if (gsiz > 1024*1024) {
      gsiz = 1024*1024;
    } else if (gsiz < 1024) {
      gsiz = 1024;
    }
    ARG3 = to;
    if (!GrowArena(arena, ArenaLimit(arena), old_sz, gsiz, 3 PASS_REGS)) {
      Yap_Error(OUT_OF_STACK_ERROR, arena, LOCAL_ErrorMessage);
      return 0L;
    }    
    to = ARG3;
    qd = RepAppl(Deref(ARG1))+1;
    arena = qd[HEAP_ARENA];
    oldH = H;
    oldHB = HB;
    H = HB = ArenaPt(arena);
    old_sz = ArenaSz(arena);    
  }
  pt = qd+HEAP_START;
  PushBeam(pt, pt+2*hmsize, hsize, key, to);
  qd[HEAP_SIZE] = Global_MkIntegerTerm(hsize+1);
  CloseArena(oldH, oldHB, ASP, qd+HEAP_ARENA, old_sz PASS_REGS);
  return TRUE;
}

static Int
p_nb_beam_del( USES_REGS1 )
{
  CELL *qd = GetHeap(ARG1,"debeam");
  UInt old_sz, qsz;
  Term arena;
  CELL *oldH, *oldHB;
  Term tk, tv;

  if (!qd)
    return FALSE;
  qsz = IntegerOfTerm(qd[HEAP_SIZE]);
  if (qsz == 0)
    return FALSE;
  arena = qd[HEAP_ARENA];
  if (arena == 0L)
    return FALSE;
  old_sz = ArenaSz(arena);
  /* garbage collection ? */
  oldH = H;
  oldHB = HB;
  qd[HEAP_SIZE] = Global_MkIntegerTerm(qsz-1);
  CloseArena(oldH, oldHB, ASP, &arena, old_sz PASS_REGS);
  tk = qd[HEAP_START];
  tv = DelBeamMin(qd+HEAP_START, qd+(HEAP_START+2*IntegerOfTerm(qd[HEAP_MAX])), qsz);
  return Yap_unify(tk, ARG2) &&
    Yap_unify(tv, ARG3);
}

#ifdef DEBUG
static Int
p_nb_beam_check( USES_REGS1 )
{
  CELL *qd = GetHeap(ARG1,"debeam");
  UInt qsz, qmax;
  CELL *pt, *pt2;
  UInt i;

  if (!qd)
    return FALSE;
  qsz = IntegerOfTerm(qd[HEAP_SIZE]);
  qmax = IntegerOfTerm(qd[HEAP_MAX]);
  if (qsz == 0)
    return TRUE;
  pt = qd+HEAP_START;
  pt2 = pt+2*qmax;
  for (i = 1; i < qsz; i++) {
    UInt back;
    if (Yap_compare_terms(pt[2*((i+1)/2-1)],pt[2*i]) > 0) {
      Yap_DebugPlWrite(pt[2*((i+1)/2-1)]); fprintf(stderr,"\n");
      Yap_DebugPlWrite(pt[2*i]); fprintf(stderr,"\n");
      fprintf(stderr,"Error at %ld\n",(unsigned long int)i);
      return FALSE;
    }
    back = IntegerOfTerm(pt[2*i+1]);
    if (IntegerOfTerm(pt2[3*back+1]) != i) {
      fprintf(stderr,"Link error at %ld\n",(unsigned long int)i);
      return FALSE;
    }
  }
  for (i = 1; i < qsz; i++) {
    if (Yap_compare_terms(pt2[3*((i+1)/2-1)],pt2[3*i]) < 0) {
      fprintf(stderr,"Error at sec %ld\n",(unsigned long int)i);
      Yap_DebugPlWrite(pt2[3*((i+1)/2-1)]); fprintf(stderr,"\n");
      Yap_DebugPlWrite(pt2[3*i]); fprintf(stderr,"\n");
      return FALSE;
    }
  }
  return TRUE;
}

#endif

static Int
p_nb_beam_keys( USES_REGS1 )
{
  CELL *qd;
  UInt qsz;
  CELL *pt, *ho;
  UInt i;

 restart:
  qd = GetHeap(ARG1,"beam_keys");
  if (!qd)
    return FALSE;
  qsz = IntegerOfTerm(qd[HEAP_SIZE]);
  ho = H;
  pt = qd+HEAP_START;
  if (qsz == 0)
    return Yap_unify(ARG2, TermNil);
  for (i=0; i < qsz; i++) {
    if (H > ASP-1024) {
      H = ho;
      if (!Yap_gcl(((ASP-H)-1024)*sizeof(CELL), 2, ENV, P)) {
	Yap_Error(OUT_OF_STACK_ERROR, TermNil, LOCAL_ErrorMessage);
	return TermNil;
      }
      goto restart;
    }
    *H++ = pt[0];
    *H = AbsPair(H+1);
    H++;
    pt += 2;
  }
  H[-1] = TermNil;
  return Yap_unify(ARG2, AbsPair(ho));
}

static Int
p_nb_beam_peek( USES_REGS1 )
{
  CELL *qd = GetHeap(ARG1,"beam_peek"), *pt, *pt2;
  UInt qsz, qbsize;
  Term tk, tv;

  if (!qd)
    return FALSE;
  qsz = IntegerOfTerm(qd[HEAP_SIZE]);
  qbsize = IntegerOfTerm(qd[HEAP_MAX]);
  if (qsz == 0)
    return FALSE;
  pt = qd+HEAP_START;
  pt2 = pt+2*qbsize;
  tk = pt[0];
  tv = pt2[2];
  return Yap_unify(tk, ARG2) &&
    Yap_unify(tv, ARG3);
}

static Int
p_nb_beam_empty( USES_REGS1 )
{
  CELL *qd = GetHeap(ARG1,"beam_empty");

  if (!qd)
    return FALSE;
  return (IntegerOfTerm(qd[HEAP_SIZE]) == 0);
}

static Int
p_nb_beam_size( USES_REGS1 )
{
  CELL *qd = GetHeap(ARG1,"beam_size");

  if (!qd)
    return FALSE;
  return Yap_unify(ARG2,qd[HEAP_SIZE]);
}

static Int 
cont_current_nb( USES_REGS1 )
{
  Int unif;
  GlobalEntry *ge = (GlobalEntry *)IntegerOfTerm(EXTRA_CBACK_ARG(1,1));

  unif = Yap_unify(MkAtomTerm(AbsAtom(ge->AtomOfGE)), ARG1);
  ge = ge->NextGE;
  if (!ge) {
    if (unif)
      cut_succeed();
    else
      cut_fail();
  } else {
    EXTRA_CBACK_ARG(1,1) =  MkIntegerTerm((Int)ge);
    return unif;
  }
}

static Int 
init_current_nb( USES_REGS1 )
{				/* current_atom(?Atom)		 */
  Term t1 = Deref(ARG1);
  if (!IsVarTerm(t1)) {
    if (IsAtomTerm(t1)) {
      if (!FindGlobalEntry(AtomOfTerm(t1) PASS_REGS)) {
	  cut_fail();
      } else {
	cut_succeed();
      }
    } else {
      Yap_Error(TYPE_ERROR_ATOM,t1,"nb_current");
      cut_fail();
    }
  }
  READ_LOCK(HashChain[0].AERWLock);
  EXTRA_CBACK_ARG(1,1) =  MkIntegerTerm((Int)LOCAL_GlobalVariables);
  return cont_current_nb( PASS_REGS1 );
}


void Yap_InitGlobals(void)
{
  CACHE_REGS
  Term cm = CurrentModule;
  Yap_InitCPred("$allocate_arena", 2, p_allocate_arena, 0);
  Yap_InitCPred("arena_size", 1, p_default_arena_size, 0);
  Yap_InitCPred("b_setval", 2, p_b_setval, SafePredFlag);
  Yap_InitCPred("nb_setval", 2, p_nb_setval, 0L);
  Yap_InitCPred("nb_set_shared_val", 2, p_nb_set_shared_val, 0L);
  Yap_InitCPred("nb_linkval", 2, p_nb_linkval, 0L);
  Yap_InitCPred("$nb_getval", 3, p_nb_getval, SafePredFlag);
  Yap_InitCPred("nb_setarg", 3, p_nb_setarg, 0L);
  Yap_InitCPred("nb_set_shared_arg", 3, p_nb_set_shared_arg, 0L);
  Yap_InitCPred("nb_linkarg", 3, p_nb_linkarg, 0L);
  Yap_InitCPred("nb_delete", 1, p_nb_delete, 0L);
  Yap_InitCPred("nb_create", 3, p_nb_create, 0L);
  Yap_InitCPred("nb_create", 4, p_nb_create2, 0L);
  Yap_InitCPredBack("$nb_current", 1, 1, init_current_nb, cont_current_nb, SafePredFlag);
  CurrentModule = GLOBALS_MODULE;
  Yap_InitCPred("nb_queue", 1, p_nb_queue, 0L);
  Yap_InitCPred("nb_queue", 2, p_nb_queue_sized, 0L);
  Yap_InitCPred("nb_queue_close", 3, p_nb_queue_close, SafePredFlag);
  Yap_InitCPred("nb_queue_enqueue", 2, p_nb_queue_enqueue, 0L);
  Yap_InitCPred("nb_queue_dequeue", 2, p_nb_queue_dequeue, SafePredFlag);
  Yap_InitCPred("nb_queue_peek", 2, p_nb_queue_peek, SafePredFlag);
  Yap_InitCPred("nb_queue_empty", 1, p_nb_queue_empty, SafePredFlag);
  Yap_InitCPred("nb_queue_replace", 3, p_nb_queue_replace, SafePredFlag);
  Yap_InitCPred("nb_queue_size", 2, p_nb_queue_size, SafePredFlag);
  Yap_InitCPred("nb_queue_show", 2, p_nb_queue_show, SafePredFlag);
  Yap_InitCPred("nb_heap", 2, p_nb_heap, 0L);
  Yap_InitCPred("nb_heap_close", 1, p_nb_heap_close, SafePredFlag);
  Yap_InitCPred("nb_heap_add", 3, p_nb_heap_add_to_heap, 0L);
  Yap_InitCPred("nb_heap_del", 3, p_nb_heap_del, SafePredFlag);
  Yap_InitCPred("nb_heap_peek", 3, p_nb_heap_peek, SafePredFlag);
  Yap_InitCPred("nb_heap_empty", 1, p_nb_heap_empty, SafePredFlag);
  Yap_InitCPred("nb_heap_size", 2, p_nb_heap_size, SafePredFlag);
  Yap_InitCPred("nb_beam", 2, p_nb_beam, 0L);
  Yap_InitCPred("nb_beam_close", 1, p_nb_beam_close, SafePredFlag);
  Yap_InitCPred("nb_beam_add", 3, p_nb_beam_add_to_beam, 0L);
  Yap_InitCPred("nb_beam_del", 3, p_nb_beam_del, SafePredFlag);
  Yap_InitCPred("nb_beam_peek", 3, p_nb_beam_peek, SafePredFlag);
  Yap_InitCPred("nb_beam_empty", 1, p_nb_beam_empty, SafePredFlag);
  Yap_InitCPred("nb_beam_keys", 2, p_nb_beam_keys, 0L);
  Yap_InitCPred("nb_create_accumulator", 2, p_nb_create_accumulator, 0L);
  Yap_InitCPred("nb_add_to_accumulator", 2, p_nb_add_to_accumulator, 0L);
  Yap_InitCPred("nb_accumulator_value", 2, p_nb_accumulator_value, 0L);
#ifdef DEBUG
  Yap_InitCPred("nb_beam_check", 1, p_nb_beam_check, SafePredFlag);
#endif
  Yap_InitCPred("nb_beam_size", 2, p_nb_beam_size, SafePredFlag);
  CurrentModule = cm;
}
