postgres/contrib/cube/cube.c

/******************************************************************************
  This file contains routines that can be bound to a Postgres backend and
  called by the backend in the process of processing queries.  The calling
  format for these routines is dictated by Postgres architecture.
******************************************************************************/

#include "postgres.h"

#include <math.h>

#include "access/gist.h"
#include "access/rtree.h"
#include "utils/elog.h"
#include "utils/palloc.h"
#include "utils/builtins.h"

#include "cubedata.h"

#define max(a,b)		((a) >	(b) ? (a) : (b))
#define min(a,b)		((a) <= (b) ? (a) : (b))
#define abs(a)			((a) <	(0) ? (-a) : (a))

extern void set_parse_buffer(char *str);
extern int	cube_yyparse();

/*
** Input/Output routines
*/
NDBOX	   *cube_in(char *str);
char	   *cube_out(NDBOX * cube);


/*
** GiST support methods
*/
bool		g_cube_consistent(GISTENTRY *entry, NDBOX * query, StrategyNumber strategy);
GISTENTRY  *g_cube_compress(GISTENTRY *entry);
GISTENTRY  *g_cube_decompress(GISTENTRY *entry);
float	   *g_cube_penalty(GISTENTRY *origentry, GISTENTRY *newentry, float *result);
GIST_SPLITVEC *g_cube_picksplit(bytea *entryvec, GIST_SPLITVEC *v);
bool		g_cube_leaf_consistent(NDBOX * key, NDBOX * query, StrategyNumber strategy);
bool		g_cube_internal_consistent(NDBOX * key, NDBOX * query, StrategyNumber strategy);
NDBOX	   *g_cube_union(bytea *entryvec, int *sizep);
NDBOX	   *g_cube_binary_union(NDBOX * r1, NDBOX * r2, int *sizep);
bool	   *g_cube_same(NDBOX * b1, NDBOX * b2, bool *result);

/*
** R-tree suport functions
*/
bool		cube_same(NDBOX * a, NDBOX * b);
bool		cube_different(NDBOX * a, NDBOX * b);
bool		cube_contains(NDBOX * a, NDBOX * b);
bool		cube_contained(NDBOX * a, NDBOX * b);
bool		cube_overlap(NDBOX * a, NDBOX * b);
NDBOX	   *cube_union(NDBOX * a, NDBOX * b);
NDBOX	   *cube_inter(NDBOX * a, NDBOX * b);
float	   *cube_size(NDBOX * a);
void		rt_cube_size(NDBOX * a, float *sz);

/*
** These make no sense for this type, but R-tree wants them
*/
bool		cube_over_left(NDBOX * a, NDBOX * b);
bool		cube_over_right(NDBOX * a, NDBOX * b);
bool		cube_left(NDBOX * a, NDBOX * b);
bool		cube_right(NDBOX * a, NDBOX * b);

/*
** miscellaneous
*/
bool		cube_lt(NDBOX * a, NDBOX * b);
bool		cube_gt(NDBOX * a, NDBOX * b);
float	   *cube_distance(NDBOX * a, NDBOX * b);

/*
** Auxiliary funxtions
*/
static float distance_1D(float a1, float a2, float b1, float b2);
static NDBOX *swap_corners(NDBOX * a);


/*****************************************************************************
 * Input/Output functions
 *****************************************************************************/

/* NdBox = [(lowerleft),(upperright)] */
/* [(xLL(1)...xLL(N)),(xUR(1)...xUR(n))] */
NDBOX *
cube_in(char *str)
{
	void	   *result;

	set_parse_buffer(str);

	if (cube_yyparse(&result) != 0)
		return NULL;

	return ((NDBOX *) result);
}

/*
 * You might have noticed a slight inconsistency between the following
 * declaration and the SQL definition:
 *	   CREATE FUNCTION cube_out(opaque) RETURNS opaque ...
 * The reason is that the argument pass into cube_out is really just a
 * pointer. POSTGRES thinks all output functions are:
 *	   char *out_func(char *);
 */
char *
cube_out(NDBOX * cube)
{
	char	   *result;
	char	   *p;
	int			equal = 1;
	int			dim = cube->dim;
	int			i;

	if (cube == NULL)
		return (NULL);

	p = result = (char *) palloc(100);

	/*
	 * while printing the first (LL) corner, check if it is equal to the
	 * scond one
	 */
	p += sprintf(p, "(");
	for (i = 0; i < dim; i++)
	{
		p += sprintf(p, "%g", cube->x[i]);
		p += sprintf(p, ", ");
		if (cube->x[i] != cube->x[i + dim])
			equal = 0;
	}
	p -= 2;						/* get rid of the last ", " */
	p += sprintf(p, ")");

	if (!equal)
	{
		p += sprintf(p, ",(");
		for (i = dim; i < dim * 2; i++)
		{
			p += sprintf(p, "%g", cube->x[i]);
			p += sprintf(p, ", ");
		}
		p -= 2;
		p += sprintf(p, ")");
	}

	return (result);
}


/*****************************************************************************
 *						   GiST functions
 *****************************************************************************/

/*
** The GiST Consistent method for boxes
** Should return false if for all data items x below entry,
** the predicate x op query == FALSE, where op is the oper
** corresponding to strategy in the pg_amop table.
*/
bool
g_cube_consistent(GISTENTRY *entry,
				  NDBOX * query,
				  StrategyNumber strategy)
{

	/*
	 * * if entry is not leaf, use g_cube_internal_consistent, * else use
	 * g_cube_leaf_consistent
	 */
	if (GIST_LEAF(entry))
		return (g_cube_leaf_consistent((NDBOX *) (entry->pred), query, strategy));
	else
		return (g_cube_internal_consistent((NDBOX *) (entry->pred), query, strategy));
}


/*
** The GiST Union method for boxes
** returns the minimal bounding box that encloses all the entries in entryvec
*/
NDBOX *
g_cube_union(bytea *entryvec, int *sizep)
{
	int			numranges,
				i;
	NDBOX	   *out = (NDBOX *) NULL;
	NDBOX	   *tmp;

	/*
	 * fprintf(stderr, "union\n");
	 */
	numranges = (VARSIZE(entryvec) - VARHDRSZ) / sizeof(GISTENTRY);
	tmp = (NDBOX *) (((GISTENTRY *) (VARDATA(entryvec)))[0]).pred;

	/*
	 * sizep = sizeof(NDBOX); -- NDBOX has variable size
	 */
	*sizep = tmp->size;

	for (i = 1; i < numranges; i++)
	{
		out = g_cube_binary_union(tmp, (NDBOX *)
						   (((GISTENTRY *) (VARDATA(entryvec)))[i]).pred,
								  sizep);

		/*
		 * fprintf(stderr, "\t%s ^ %s -> %s\n", cube_out(tmp),
		 * cube_out((NDBOX *)(((GISTENTRY
		 * *)(VARDATA(entryvec)))[i]).pred), cube_out(out));
		 */
		if (i > 1)
			pfree(tmp);
		tmp = out;
	}

	return (out);
}

/*
** GiST Compress and Decompress methods for boxes
** do not do anything.
*/
GISTENTRY  *
g_cube_compress(GISTENTRY *entry)
{
	return (entry);
}

GISTENTRY  *
g_cube_decompress(GISTENTRY *entry)
{
	return (entry);
}

/*
** The GiST Penalty method for boxes
** As in the R-tree paper, we use change in area as our penalty metric
*/
float *
g_cube_penalty(GISTENTRY *origentry, GISTENTRY *newentry, float *result)
{
	Datum		ud;
	float		tmp1,
				tmp2;

	ud = (Datum) cube_union((NDBOX *) (origentry->pred), (NDBOX *) (newentry->pred));
	rt_cube_size((NDBOX *) ud, &tmp1);
	rt_cube_size((NDBOX *) (origentry->pred), &tmp2);
	*result = tmp1 - tmp2;
	pfree((char *) ud);

	/*
	 * fprintf(stderr, "penalty\n"); fprintf(stderr, "\t%g\n", *result);
	 */
	return (result);
}



/*
** The GiST PickSplit method for boxes
** We use Guttman's poly time split algorithm
*/
GIST_SPLITVEC *
g_cube_picksplit(bytea *entryvec,
				 GIST_SPLITVEC *v)
{
	OffsetNumber i,
				j;
	NDBOX	   *datum_alpha,
			   *datum_beta;
	NDBOX	   *datum_l,
			   *datum_r;
	NDBOX	   *union_d,
			   *union_dl,
			   *union_dr;
	NDBOX	   *inter_d;
	bool		firsttime;
	float		size_alpha,
				size_beta,
				size_union,
				size_inter;
	float		size_waste,
				waste;
	float		size_l,
				size_r;
	int			nbytes;
	OffsetNumber seed_1 = 0,
				seed_2 = 0;
	OffsetNumber *left,
			   *right;
	OffsetNumber maxoff;

	/*
	 * fprintf(stderr, "picksplit\n");
	 */
	maxoff = ((VARSIZE(entryvec) - VARHDRSZ) / sizeof(GISTENTRY)) - 2;
	nbytes = (maxoff + 2) * sizeof(OffsetNumber);
	v->spl_left = (OffsetNumber *) palloc(nbytes);
	v->spl_right = (OffsetNumber *) palloc(nbytes);

	firsttime = true;
	waste = 0.0;

	for (i = FirstOffsetNumber; i < maxoff; i = OffsetNumberNext(i))
	{
		datum_alpha = (NDBOX *) (((GISTENTRY *) (VARDATA(entryvec)))[i].pred);
		for (j = OffsetNumberNext(i); j <= maxoff; j = OffsetNumberNext(j))
		{
			datum_beta = (NDBOX *) (((GISTENTRY *) (VARDATA(entryvec)))[j].pred);

			/* compute the wasted space by unioning these guys */
			/* size_waste = size_union - size_inter; */
			union_d = (NDBOX *) cube_union(datum_alpha, datum_beta);
			rt_cube_size(union_d, &size_union);
			inter_d = (NDBOX *) cube_inter(datum_alpha, datum_beta);
			rt_cube_size(inter_d, &size_inter);
			size_waste = size_union - size_inter;

			pfree(union_d);

			if (inter_d != (NDBOX *) NULL)
				pfree(inter_d);

			/*
			 * are these a more promising split than what we've already
			 * seen?
			 */

			if (size_waste > waste || firsttime)
			{
				waste = size_waste;
				seed_1 = i;
				seed_2 = j;
				firsttime = false;
			}
		}
	}

	left = v->spl_left;
	v->spl_nleft = 0;
	right = v->spl_right;
	v->spl_nright = 0;

	datum_alpha = (NDBOX *) (((GISTENTRY *) (VARDATA(entryvec)))[seed_1].pred);
	datum_l = (NDBOX *) cube_union(datum_alpha, datum_alpha);
	rt_cube_size((NDBOX *) datum_l, &size_l);
	datum_beta = (NDBOX *) (((GISTENTRY *) (VARDATA(entryvec)))[seed_2].pred);;
	datum_r = (NDBOX *) cube_union(datum_beta, datum_beta);
	rt_cube_size((NDBOX *) datum_r, &size_r);

	/*
	 * Now split up the regions between the two seeds.	An important
	 * property of this split algorithm is that the split vector v has the
	 * indices of items to be split in order in its left and right
	 * vectors.  We exploit this property by doing a merge in the code
	 * that actually splits the page.
	 *
	 * For efficiency, we also place the new index tuple in this loop. This
	 * is handled at the very end, when we have placed all the existing
	 * tuples and i == maxoff + 1.
	 */

	maxoff = OffsetNumberNext(maxoff);
	for (i = FirstOffsetNumber; i <= maxoff; i = OffsetNumberNext(i))
	{

		/*
		 * If we've already decided where to place this item, just put it
		 * on the right list.  Otherwise, we need to figure out which page
		 * needs the least enlargement in order to store the item.
		 */

		if (i == seed_1)
		{
			*left++ = i;
			v->spl_nleft++;
			continue;
		}
		else if (i == seed_2)
		{
			*right++ = i;
			v->spl_nright++;
			continue;
		}

		/* okay, which page needs least enlargement? */
		datum_alpha = (NDBOX *) (((GISTENTRY *) (VARDATA(entryvec)))[i].pred);
		union_dl = (NDBOX *) cube_union(datum_l, datum_alpha);
		union_dr = (NDBOX *) cube_union(datum_r, datum_alpha);
		rt_cube_size((NDBOX *) union_dl, &size_alpha);
		rt_cube_size((NDBOX *) union_dr, &size_beta);

		/* pick which page to add it to */
		if (size_alpha - size_l < size_beta - size_r)
		{
			pfree(datum_l);
			pfree(union_dr);
			datum_l = union_dl;
			size_l = size_alpha;
			*left++ = i;
			v->spl_nleft++;
		}
		else
		{
			pfree(datum_r);
			pfree(union_dl);
			datum_r = union_dr;
			size_r = size_alpha;
			*right++ = i;
			v->spl_nright++;
		}
	}
	*left = *right = FirstOffsetNumber; /* sentinel value, see dosplit() */

	v->spl_ldatum = (char *) datum_l;
	v->spl_rdatum = (char *) datum_r;

	return v;
}

/*
** Equality method
*/
bool *
g_cube_same(NDBOX * b1, NDBOX * b2, bool *result)
{
	if (cube_same(b1, b2))
		*result = TRUE;
	else
		*result = FALSE;

	/*
	 * fprintf(stderr, "same: %s\n", (*result ? "TRUE" : "FALSE" ));
	 */
	return (result);
}

/*
** SUPPORT ROUTINES
*/
bool
g_cube_leaf_consistent(NDBOX * key,
					   NDBOX * query,
					   StrategyNumber strategy)
{
	bool		retval;

	/*
	 * fprintf(stderr, "leaf_consistent, %d\n", strategy);
	 */
	switch (strategy)
	{
		case RTLeftStrategyNumber:
			retval = (bool) cube_left(key, query);
			break;
		case RTOverLeftStrategyNumber:
			retval = (bool) cube_over_left(key, query);
			break;
		case RTOverlapStrategyNumber:
			retval = (bool) cube_overlap(key, query);
			break;
		case RTOverRightStrategyNumber:
			retval = (bool) cube_over_right(key, query);
			break;
		case RTRightStrategyNumber:
			retval = (bool) cube_right(key, query);
			break;
		case RTSameStrategyNumber:
			retval = (bool) cube_same(key, query);
			break;
		case RTContainsStrategyNumber:
			retval = (bool) cube_contains(key, query);
			break;
		case RTContainedByStrategyNumber:
			retval = (bool) cube_contained(key, query);
			break;
		default:
			retval = FALSE;
	}
	return (retval);
}

bool
g_cube_internal_consistent(NDBOX * key,
						   NDBOX * query,
						   StrategyNumber strategy)
{
	bool		retval;

	/*
	 * fprintf(stderr, "internal_consistent, %d\n", strategy);
	 */
	switch (strategy)
	{
		case RTLeftStrategyNumber:
		case RTOverLeftStrategyNumber:
			retval = (bool) cube_over_left(key, query);
			break;
		case RTOverlapStrategyNumber:
			retval = (bool) cube_overlap(key, query);
			break;
		case RTOverRightStrategyNumber:
		case RTRightStrategyNumber:
			retval = (bool) cube_right(key, query);
			break;
		case RTSameStrategyNumber:
		case RTContainsStrategyNumber:
			retval = (bool) cube_contains(key, query);
			break;
		case RTContainedByStrategyNumber:
			retval = (bool) cube_overlap(key, query);
			break;
		default:
			retval = FALSE;
	}
	return (retval);
}

NDBOX *
g_cube_binary_union(NDBOX * r1, NDBOX * r2, int *sizep)
{
	NDBOX	   *retval;

	retval = cube_union(r1, r2);
	*sizep = retval->size;

	return (retval);
}


/* cube_union */
NDBOX *
cube_union(NDBOX * box_a, NDBOX * box_b)
{
	int			i;
	NDBOX	   *result;
	NDBOX	   *a = swap_corners(box_a);
	NDBOX	   *b = swap_corners(box_b);

	if (a->dim >= b->dim)
	{
		result = palloc(a->size);
		result->size = a->size;
		result->dim = a->dim;
	}
	else
	{
		result = palloc(b->size);
		result->size = b->size;
		result->dim = b->dim;
	}

	/* swap the box pointers if needed */
	if (a->dim < b->dim)
	{
		NDBOX	   *tmp = b;

		b = a;
		a = tmp;
	}

	/*
	 * use the potentially smaller of the two boxes (b) to fill in the
	 * result, padding absent dimensions with zeroes
	 */
	for (i = 0; i < b->dim; i++)
	{
		result->x[i] = b->x[i];
		result->x[i + a->dim] = b->x[i + b->dim];
	}
	for (i = b->dim; i < a->dim; i++)
	{
		result->x[i] = 0;
		result->x[i + a->dim] = 0;
	}

	/* compute the union */
	for (i = 0; i < a->dim; i++)
		result->x[i] = min(a->x[i], result->x[i]);
	for (i = a->dim; i < a->dim * 2; i++)
		result->x[i] = max(a->x[i], result->x[i]);

	pfree(a);
	pfree(b);

	return (result);
}

/* cube_inter */
NDBOX *
cube_inter(NDBOX * box_a, NDBOX * box_b)
{
	int			i;
	NDBOX	   *result;
	NDBOX	   *a = swap_corners(box_a);
	NDBOX	   *b = swap_corners(box_b);

	if (a->dim >= b->dim)
	{
		result = palloc(a->size);
		result->size = a->size;
		result->dim = a->dim;
	}
	else
	{
		result = palloc(b->size);
		result->size = b->size;
		result->dim = b->dim;
	}

	/* swap the box pointers if needed */
	if (a->dim < b->dim)
	{
		NDBOX	   *tmp = b;

		b = a;
		a = tmp;
	}

	/*
	 * use the potentially	smaller of the two boxes (b) to fill in the
	 * result, padding absent dimensions with zeroes
	 */
	for (i = 0; i < b->dim; i++)
	{
		result->x[i] = b->x[i];
		result->x[i + a->dim] = b->x[i + b->dim];
	}
	for (i = b->dim; i < a->dim; i++)
	{
		result->x[i] = 0;
		result->x[i + a->dim] = 0;
	}

	/* compute the intersection */
	for (i = 0; i < a->dim; i++)
		result->x[i] = max(a->x[i], result->x[i]);
	for (i = a->dim; i < a->dim * 2; i++)
		result->x[i] = min(a->x[i], result->x[i]);

	pfree(a);
	pfree(b);

	/*
	 * Is it OK to return a non-null intersection for non-overlapping
	 * boxes?
	 */
	return (result);
}

/* cube_size */
float *
cube_size(NDBOX * a)
{
	int			i,
				j;
	float	   *result;

	result = (float *) palloc(sizeof(float));

	*result = 1.0;
	for (i = 0, j = a->dim; i < a->dim; i++, j++)
		*result = (*result) * abs((a->x[j] - a->x[i]));

	return (result);
}

void
rt_cube_size(NDBOX * a, float *size)
{
	int			i,
				j;

	if (a == (NDBOX *) NULL)
		*size = 0.0;
	else
	{
		*size = 1.0;
		for (i = 0, j = a->dim; i < a->dim; i++, j++)
			*size = (*size) * abs((a->x[j] - a->x[i]));
	}
	return;
}

/* The following four methods compare the projections of the boxes
   onto the 0-th coordinate axis. These methods are useless for dimensions
   larger than 2, but it seems that R-tree requires all its strategies
   map to real functions that return something */

/*	is the right edge of (a) located to the left of
	the right edge of (b)? */
bool
cube_over_left(NDBOX * box_a, NDBOX * box_b)
{
	NDBOX	   *a;
	NDBOX	   *b;

	if ((box_a == NULL) || (box_b == NULL))
		return (FALSE);

	a = swap_corners(box_a);
	b = swap_corners(box_b);

	return (a->x[a->dim - 1] <= b->x[b->dim - 1] && !cube_left(a, b) && !cube_right(a, b));
}

/*	is the left edge of (a) located to the right of
	the left edge of (b)? */
bool
cube_over_right(NDBOX * box_a, NDBOX * box_b)
{
	NDBOX	   *a;
	NDBOX	   *b;

	if ((box_a == NULL) || (box_b == NULL))
		return (FALSE);

	a = swap_corners(box_a);
	b = swap_corners(box_b);

	return (a->x[a->dim - 1] >= b->x[b->dim - 1] && !cube_left(a, b) && !cube_right(a, b));
}


/* return 'true' if the projection of 'a' is
   entirely on the left of the projection of 'b' */
bool
cube_left(NDBOX * box_a, NDBOX * box_b)
{
	NDBOX	   *a;
	NDBOX	   *b;

	if ((box_a == NULL) || (box_b == NULL))
		return (FALSE);

	a = swap_corners(box_a);
	b = swap_corners(box_b);

	return (a->x[a->dim - 1] < b->x[0]);
}

/* return 'true' if the projection of 'a' is
   entirely on the right  of the projection of 'b' */
bool
cube_right(NDBOX * box_a, NDBOX * box_b)
{
	NDBOX	   *a;
	NDBOX	   *b;

	if ((box_a == NULL) || (box_b == NULL))
		return (FALSE);

	a = swap_corners(box_a);
	b = swap_corners(box_b);

	return (a->x[0] > b->x[b->dim - 1]);
}

/* make up a metric in which one box will be 'lower' than the other
   -- this can be useful for srting and to determine uniqueness */
bool
cube_lt(NDBOX * box_a, NDBOX * box_b)
{
	int			i;
	int			dim;
	NDBOX	   *a;
	NDBOX	   *b;

	if ((box_a == NULL) || (box_b == NULL))
		return (FALSE);

	a = swap_corners(box_a);
	b = swap_corners(box_b);
	dim = min(a->dim, b->dim);

	/*
	 * if all common dimensions are equal, the cube with more dimensions
	 * wins
	 */
	if (cube_same(a, b))
	{
		if (a->dim < b->dim)
			return (TRUE);
		else
			return (FALSE);
	}

	/* compare the common dimensions */
	for (i = 0; i < dim; i++)
	{
		if (a->x[i] > b->x[i])
			return (FALSE);
		if (a->x[i] < b->x[i])
			return (TRUE);
	}
	for (i = 0; i < dim; i++)
	{
		if (a->x[i + a->dim] > b->x[i + b->dim])
			return (FALSE);
		if (a->x[i + a->dim] < b->x[i + b->dim])
			return (TRUE);
	}

	/* compare extra dimensions to zero */
	if (a->dim > b->dim)
	{
		for (i = dim; i < a->dim; i++)
		{
			if (a->x[i] > 0)
				return (FALSE);
			if (a->x[i] < 0)
				return (TRUE);
		}
		for (i = 0; i < dim; i++)
		{
			if (a->x[i + a->dim] > 0)
				return (FALSE);
			if (a->x[i + a->dim] < 0)
				return (TRUE);
		}
	}
	if (a->dim < b->dim)
	{
		for (i = dim; i < b->dim; i++)
		{
			if (b->x[i] > 0)
				return (TRUE);
			if (b->x[i] < 0)
				return (FALSE);
		}
		for (i = 0; i < dim; i++)
		{
			if (b->x[i + b->dim] > 0)
				return (TRUE);
			if (b->x[i + b->dim] < 0)
				return (FALSE);
		}
	}

	return (FALSE);
}


bool
cube_gt(NDBOX * box_a, NDBOX * box_b)
{
	int			i;
	int			dim;
	NDBOX	   *a;
	NDBOX	   *b;

	if ((box_a == NULL) || (box_b == NULL))
		return (FALSE);

	a = swap_corners(box_a);
	b = swap_corners(box_b);
	dim = min(a->dim, b->dim);

	/*
	 * if all common dimensions are equal, the cube with more dimensions
	 * wins
	 */
	if (cube_same(a, b))
	{
		if (a->dim > b->dim)
			return (TRUE);
		else
			return (FALSE);
	}

	/* compare the common dimensions */
	for (i = 0; i < dim; i++)
	{
		if (a->x[i] < b->x[i])
			return (FALSE);
		if (a->x[i] > b->x[i])
			return (TRUE);
	}
	for (i = 0; i < dim; i++)
	{
		if (a->x[i + a->dim] < b->x[i + b->dim])
			return (FALSE);
		if (a->x[i + a->dim] > b->x[i + b->dim])
			return (TRUE);
	}


	/* compare extra dimensions to zero */
	if (a->dim > b->dim)
	{
		for (i = dim; i < a->dim; i++)
		{
			if (a->x[i] < 0)
				return (FALSE);
			if (a->x[i] > 0)
				return (TRUE);
		}
		for (i = 0; i < dim; i++)
		{
			if (a->x[i + a->dim] < 0)
				return (FALSE);
			if (a->x[i + a->dim] > 0)
				return (TRUE);
		}
	}
	if (a->dim < b->dim)
	{
		for (i = dim; i < b->dim; i++)
		{
			if (b->x[i] < 0)
				return (TRUE);
			if (b->x[i] > 0)
				return (FALSE);
		}
		for (i = 0; i < dim; i++)
		{
			if (b->x[i + b->dim] < 0)
				return (TRUE);
			if (b->x[i + b->dim] > 0)
				return (FALSE);
		}
	}

	return (FALSE);
}


/* Equal */
bool
cube_same(NDBOX * box_a, NDBOX * box_b)
{
	int			i;
	NDBOX	   *a;
	NDBOX	   *b;

	if ((box_a == NULL) || (box_b == NULL))
		return (FALSE);

	a = swap_corners(box_a);
	b = swap_corners(box_b);

	/* swap the box pointers if necessary */
	if (a->dim < b->dim)
	{
		NDBOX	   *tmp = b;

		b = a;
		a = tmp;
	}

	for (i = 0; i < b->dim; i++)
	{
		if (a->x[i] != b->x[i])
			return (FALSE);
		if (a->x[i + a->dim] != b->x[i + b->dim])
			return (FALSE);
	}

	/*
	 * all dimensions of (b) are compared to those of (a); instead of
	 * those in (a) absent in (b), compare (a) to zero
	 */
	for (i = b->dim; i < a->dim; i++)
	{
		if (a->x[i] != 0)
			return (FALSE);
		if (a->x[i + a->dim] != 0)
			return (FALSE);
	}

	pfree(a);
	pfree(b);

	return (TRUE);
}

/* Different */
bool
cube_different(NDBOX * box_a, NDBOX * box_b)
{
	return (!cube_same(box_a, box_b));
}


/* Contains */
/* Box(A) CONTAINS Box(B) IFF pt(A) < pt(B) */
bool
cube_contains(NDBOX * box_a, NDBOX * box_b)
{
	int			i;
	NDBOX	   *a;
	NDBOX	   *b;

	if ((box_a == NULL) || (box_b == NULL))
		return (FALSE);

	a = swap_corners(box_a);
	b = swap_corners(box_b);

	if (a->dim < b->dim)
	{

		/*
		 * the further comparisons will make sense if the excess
		 * dimensions of (b) were zeroes
		 */
		for (i = a->dim; i < b->dim; i++)
		{
			if (b->x[i] != 0)
				return (FALSE);
			if (b->x[i + b->dim] != 0)
				return (FALSE);
		}
	}

	/* Can't care less about the excess dimensions of (a), if any */
	for (i = 0; i < min(a->dim, b->dim); i++)
	{
		if (a->x[i] > b->x[i])
			return (FALSE);
		if (a->x[i + a->dim] < b->x[i + b->dim])
			return (FALSE);
	}

	pfree(a);
	pfree(b);

	return (TRUE);
}

/* Contained */
/* Box(A) Contained by Box(B) IFF Box(B) Contains Box(A) */
bool
cube_contained(NDBOX * a, NDBOX * b)
{
	if (cube_contains(b, a) == TRUE)
		return (TRUE);
	else
		return (FALSE);
}

/* Overlap */
/* Box(A) Overlap Box(B) IFF (pt(a)LL < pt(B)UR) && (pt(b)LL < pt(a)UR) */
bool
cube_overlap(NDBOX * box_a, NDBOX * box_b)
{
	int			i;
	NDBOX	   *a;
	NDBOX	   *b;

	/*
	 * This *very bad* error was found in the source: if ( (a==NULL) ||
	 * (b=NULL) ) return(FALSE);
	 */
	if ((box_a == NULL) || (box_b == NULL))
		return (FALSE);

	a = swap_corners(box_a);
	b = swap_corners(box_b);

	/* swap the box pointers if needed */
	if (a->dim < b->dim)
	{
		NDBOX	   *tmp = b;

		b = a;
		a = tmp;
	}

	/* compare within the dimensions of (b) */
	for (i = 0; i < b->dim; i++)
	{
		if (a->x[i] > b->x[i + b->dim])
			return (FALSE);
		if (a->x[i + a->dim] < b->x[i])
			return (FALSE);
	}

	/* compare to zero those dimensions in (a) absent in (b) */
	for (i = b->dim; i < a->dim; i++)
	{
		if (a->x[i] > 0)
			return (FALSE);
		if (a->x[i + a->dim] < 0)
			return (FALSE);
	}

	pfree(a);
	pfree(b);

	return (TRUE);
}


/* Distance */
/* The distance is computed as a per axis sum of the squared distances
   between 1D projections of the boxes onto Cartesian axes. Assuming zero
   distance between overlapping projections, this metric coincides with the
   "common sense" geometric distance */
float *
cube_distance(NDBOX * a, NDBOX * b)
{
	int			i;
	double		d,
				distance;
	float	   *result;

	result = (float *) palloc(sizeof(float));

	/* swap the box pointers if needed */
	if (a->dim < b->dim)
	{
		NDBOX	   *tmp = b;

		b = a;
		a = tmp;
	}

	distance = 0.0;
	/* compute within the dimensions of (b) */
	for (i = 0; i < b->dim; i++)
	{
		d = distance_1D(a->x[i], a->x[i + a->dim], b->x[i], b->x[i + b->dim]);
		distance += d * d;
	}

	/* compute distance to zero for those dimensions in (a) absent in (b) */
	for (i = b->dim; i < a->dim; i++)
	{
		d = distance_1D(a->x[i], a->x[i + a->dim], 0.0, 0.0);
		distance += d * d;
	}

	*result = (float) sqrt(distance);

	return (result);
}

static float
distance_1D(float a1, float a2, float b1, float b2)
{
	/* interval (a) is entirely on the left of (b) */
	if ((a1 <= b1) && (a2 <= b1) && (a1 <= b2) && (a2 <= b2))
		return (min(b1, b2) - max(a1, a2));

	/* interval (a) is entirely on the right of (b) */
	if ((a1 > b1) && (a2 > b1) && (a1 > b2) && (a2 > b2))
		return (min(a1, a2) - max(b1, b2));

	/* the rest are all sorts of intersections */
	return (0.0);
}

/* normalize the box's co-ordinates by placing min(xLL,xUR) to LL
   and max(xLL,xUR) to UR
*/
static NDBOX *
swap_corners(NDBOX * a)
{
	int			i,
				j;
	NDBOX	   *result;

	result = palloc(a->size);
	result->size = a->size;
	result->dim = a->dim;

	for (i = 0, j = a->dim; i < a->dim; i++, j++)
	{
		result->x[i] = min(a->x[i], a->x[j]);
		result->x[j] = max(a->x[i], a->x[j]);
	}

	return (result);
}