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// Copyright Vespa.ai. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
#include <vespa/vespalib/geo/zcurve.h>
#include <vespa/vespalib/util/priority_queue.h>
#include <vespa/vespalib/util/fiddle.h>
#include <algorithm>
#include <limits>
namespace vespalib::geo {
namespace {
/**
* An area defined by its upper left and lower right corners. The
* z-coordinates between these corners act as a spacial
* over-estimation of the actual area. These areas may never cross
* signed borders, since that would break the whole concept of
* hierarchical spatial partitioning.
**/
struct Area {
const ZCurve::Point min;
const ZCurve::Point max;
Area(const Area &rhs) = default;
Area(int32_t min_x, int32_t min_y,
int32_t max_x, int32_t max_y)
: min(min_x, min_y), max(max_x, max_y)
{
assert((min_x <= max_x) && ((min_x < 0) == (max_x < 0)));
assert((min_y <= max_y) && ((min_y < 0) == (max_y < 0)));
}
Area &operator=(Area &&rhs) { new ((void*)this) Area(rhs); return *this; }
int64_t size() const { return (static_cast<int64_t>(max.x) - min.x + 1) * (static_cast<int64_t>(max.y) - min.y + 1); }
int64_t estimate() const { return (max.z - min.z + 1); }
int64_t error() const { return estimate() - size(); }
};
class ZAreaQueue
{
private:
struct MaxAreaErrorCmp {
bool operator()(const Area &a, const Area &b) const {
return (a.error() > b.error());
}
};
using Range = ZCurve::Range;
using RangeVector = ZCurve::RangeVector;
using Queue = PriorityQueue<Area, MaxAreaErrorCmp, LeftArrayHeap>;
Queue _queue;
int64_t _total_estimate;
public:
ZAreaQueue() : _queue(), _total_estimate(0) {}
int64_t total_estimate() const { return _total_estimate; }
void put(Area area) {
_total_estimate += std::min(area.estimate(), std::numeric_limits<int64_t>::max() - _total_estimate);
_queue.push(std::move(area));
}
Area get() {
assert(!_queue.empty());
Area area(_queue.front());
_queue.pop_front();
_total_estimate -= area.estimate();
return area;
}
size_t size() const { return _queue.size(); }
RangeVector extract_ranges() {
RangeVector ranges;
ranges.reserve(_queue.size());
while (!_queue.empty()) {
const Area &area = _queue.any();
ranges.push_back(Range(area.min.z, area.max.z));
_queue.pop_any();
}
return ranges;
}
};
class ZAreaSplitter
{
private:
using RangeVector = ZCurve::RangeVector;
ZAreaQueue _queue;
public:
ZAreaSplitter(int min_x, int min_y, int max_x, int max_y) : _queue() {
assert(min_x <= max_x);
assert(min_y <= max_y);
bool cross_x = (min_x < 0) != (max_x < 0);
bool cross_y = (min_y < 0) != (max_y < 0);
if (cross_x) {
if (cross_y) {
_queue.put(Area(min_x, min_y, -1, -1));
_queue.put(Area( 0, min_y, max_x, -1));
_queue.put(Area(min_x, 0, -1, max_y));
_queue.put(Area( 0, 0, max_x, max_y));
} else {
_queue.put(Area(min_x, min_y, -1, max_y));
_queue.put(Area( 0, min_y, max_x, max_y));
}
} else {
if (cross_y) {
_queue.put(Area(min_x, min_y, max_x, -1));
_queue.put(Area(min_x, 0, max_x, max_y));
} else {
_queue.put(Area(min_x, min_y, max_x, max_y));
}
}
}
size_t num_ranges() const { return _queue.size(); }
int64_t total_estimate() const { return _queue.total_estimate(); }
void split_worst() {
Area area = _queue.get();
uint32_t x_first_max, x_last_min;
uint32_t y_first_max, y_last_min;
uint32_t x_bits = bits::split_range(area.min.x, area.max.x, x_first_max, x_last_min);
uint32_t y_bits = bits::split_range(area.min.y, area.max.y, y_first_max, y_last_min);
if (x_bits > y_bits) {
_queue.put(Area(area.min.x, area.min.y, x_first_max, area.max.y));
_queue.put(Area(x_last_min, area.min.y, area.max.x, area.max.y));
} else {
assert(y_bits > 0);
_queue.put(Area(area.min.x, area.min.y, area.max.x, y_first_max));
_queue.put(Area(area.min.x, y_last_min, area.max.x, area.max.y));
}
}
RangeVector extract_ranges() { return _queue.extract_ranges(); }
};
} // namespace vespalib::geo::<unnamed>
ZCurve::BoundingBox::BoundingBox(int32_t minx,
int32_t maxx,
int32_t miny,
int32_t maxy)
: _zMinx(ZCurve::encode(minx, 0)),
_zMaxx(ZCurve::encode(maxx, 0)),
_zMiny(ZCurve::encode(0, miny)),
_zMaxy(ZCurve::encode(0, maxy))
{
}
ZCurve::RangeVector
ZCurve::find_ranges(int min_x, int min_y,
int max_x, int max_y)
{
uint64_t x_size = (static_cast<int64_t>(max_x) - min_x + 1);
uint64_t y_size = (static_cast<int64_t>(max_y) - min_y + 1);
uint64_t total_size = (x_size > std::numeric_limits<uint32_t>::max() &&
y_size > std::numeric_limits<uint32_t>::max()) ?
std::numeric_limits<uint64_t>::max() :
(x_size * y_size);
int64_t estimate_target = (total_size > std::numeric_limits<int64_t>::max() / 4) ?
std::numeric_limits<int64_t>::max() :
(total_size * 4);
ZAreaSplitter splitter(min_x, min_y, max_x, max_y);
while (splitter.total_estimate() > estimate_target && splitter.num_ranges() < 42) {
splitter.split_worst();
}
RangeVector ranges = splitter.extract_ranges();
std::sort(ranges.begin(), ranges.end());
return ranges;
}
int64_t
ZCurve::encodeSlow(int32_t x, int32_t y)
{
uint64_t res = 0;
uint32_t ibit = 1;
uint64_t obit = 1;
for (;
ibit != 0;
ibit <<= 1, obit <<= 2)
{
if (static_cast<uint32_t>(x) & ibit)
res |= obit;
if (static_cast<uint32_t>(y) & ibit)
res |= (obit << 1);
}
return static_cast<int64_t>(res);
}
void
ZCurve::decodeSlow(int64_t enc, int32_t *xp, int32_t *yp)
{
uint32_t x = 0;
uint32_t y = 0;
uint64_t ibit = 1;
uint32_t obit = 1;
for (;
ibit != 0;
ibit <<= 2, obit <<= 1)
{
if ((static_cast<uint64_t>(enc) & ibit) != 0)
x |= obit;
if ((static_cast<uint64_t>(enc) & (ibit << 1)) != 0)
y |= obit;
}
*xp = static_cast<int32_t>(x);
*yp = static_cast<int32_t>(y);
}
}
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