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Improve memory usage when computing the true bounding box #25

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Merged
lesserwhirls merged 1 commit into from
Jul 8, 2026
Merged

Improve memory usage when computing the true bounding box #25

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89 changes: 61 additions & 28 deletions cdm/src/main/java/uk/ac/rdg/resc/edal/grid/cdm/CdmTransformedGrid.java
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Original file line number Diff line number Diff line change
Expand Up @@ -31,18 +31,22 @@
import java.util.Collections;
import java.util.List;

import java.util.Objects;
import org.apache.sis.metadata.iso.extent.DefaultGeographicBoundingBox;
import org.ehcache.Cache;
import org.ehcache.config.builders.CacheConfigurationBuilder;
import org.ehcache.config.builders.ResourcePoolsBuilder;
import org.opengis.metadata.extent.GeographicBoundingBox;
import org.opengis.referencing.crs.CoordinateReferenceSystem;

import ucar.nc2.dataset.CoordinateAxis1D;
import ucar.nc2.dt.GridCoordSystem;
import ucar.unidata.geoloc.LatLonPoint;
import ucar.unidata.geoloc.LatLonRect;
import ucar.unidata.geoloc.Projection;
import ucar.unidata.geoloc.ProjectionImpl;
import ucar.unidata.geoloc.ProjectionPoint;
import ucar.unidata.geoloc.projection.RotatedPole;
import uk.ac.rdg.resc.edal.cache.EdalCache;
import uk.ac.rdg.resc.edal.domain.Extent;
import uk.ac.rdg.resc.edal.geometry.BoundingBox;
import uk.ac.rdg.resc.edal.geometry.BoundingBoxImpl;
Expand All @@ -68,6 +72,11 @@
*/
public class CdmTransformedGrid extends AbstractTransformedGrid {
private static final long serialVersionUID = 1L;

private static final int MAX_HEAP_ENTRIES = 50;
private static final String CACHE_NAME = "BBOX_CACHE";
private static final Cache<Integer, BoundingBox> bboxCache;

private final ProjectionImpl proj;
private final ReferenceableAxis<Double> xAxis;

Expand All @@ -76,6 +85,19 @@ public class CdmTransformedGrid extends AbstractTransformedGrid {

private transient Array2D<GridCell2D> domainObjs = null;

static {
Cache<Integer, BoundingBox> existing = EdalCache.cacheManager
.getCache("BBOX_CACHE", Integer.class, BoundingBox.class);
if (existing == null) {
bboxCache = EdalCache.cacheManager.createCache(CACHE_NAME,
CacheConfigurationBuilder.newCacheConfigurationBuilder(Integer.class,
BoundingBox.class,
ResourcePoolsBuilder.heap(MAX_HEAP_ENTRIES)));
} else {
bboxCache = existing;
}
}

/**
* Create a new {@link CdmTransformedGrid} from a defined
* {@link ProjectionImpl} and a pair of axes
Expand Down Expand Up @@ -133,44 +155,50 @@ public CdmTransformedGrid(GridCoordSystem coordSys) {
xAxis = CdmUtils.createReferenceableAxis((CoordinateAxis1D) coordSys.getXHorizAxis(),
xAxisIsLongitude);
yAxis = CdmUtils.createReferenceableAxis((CoordinateAxis1D) coordSys.getYHorizAxis());

List<HorizontalPosition> gridPoints = new ArrayList<>();
for(Double x : xAxis.getCoordinateValues()) {
for(Double y : yAxis.getCoordinateValues() ) {
LatLonPoint ll = proj.projToLatLon(x, y);
gridPoints.add(new HorizontalPosition(ll.getLongitude(), ll.getLatitude()));
// create the key for the bbox cache
final int hcsHash = Objects.hash(xAxis, yAxis);
if (!bboxCache.containsKey(hcsHash)) {
// compute the bounding box (can be expensive for large grids)
System.out.println("Computing bounding box for grid with hash " + hcsHash);
double latMin = Double.MAX_VALUE;
double lonMin = Double.MAX_VALUE;
double latMax = Double.MIN_VALUE;
double lonMax = Double.MIN_VALUE;

for (Double x : xAxis.getCoordinateValues()) {
for (Double y : yAxis.getCoordinateValues()) {
LatLonPoint ll = proj.projToLatLon(x, y);
lonMin = Math.min(lonMin, ll.getLongitude());
lonMax = Math.max(lonMax, ll.getLongitude());
latMin = Math.min(latMin, ll.getLatitude());
latMax = Math.max(latMax, ll.getLatitude());
}
}
}

BoundingBox latLonBoundingBox = GISUtils.getBoundingBox(gridPoints);
/*
* Some projections do not have a well-defined lat-lon bounding box and
* return NaNs. In these cases, we fall back to using global limits
*/
double lonMin = latLonBoundingBox.getMinX();
double lonMax = latLonBoundingBox.getMaxX();
double latMin = latLonBoundingBox.getMinY();
double latMax = latLonBoundingBox.getMaxY();
if (Double.isNaN(lonMin)) {
/*
* Some projections do not have a well-defined lat-lon bounding box and
* return NaNs. In these cases, we fall back to using global limits
*/
if (Double.isNaN(lonMin)) {
lonMin = -180.0;
}
if (Double.isNaN(lonMax)) {
}
if (Double.isNaN(lonMax)) {
lonMax = 180.0;
}
if (Double.isNaN(latMin) || Math.abs(latMin + 90) < 1) {
}
if (Double.isNaN(latMin) || Math.abs(latMin + 90) < 1) {
latMin = -90.0;
}
if (Double.isNaN(latMax) || Math.abs(latMax - 90) < 1) {
}
if (Double.isNaN(latMax) || Math.abs(latMax - 90) < 1) {
latMax = 90.0;
}
}

if (latMin != latMax && lonMin != lonMax) {
if (latMin != latMax && lonMin != lonMax) {
/*
* The normal situation - use the bounds to create the bounding box
*/
bbox = new BoundingBoxImpl(lonMin, latMin, lonMax, latMax,
GISUtils.defaultGeographicCRS());
} else {
GISUtils.defaultGeographicCRS());
} else {
/*
* Some projections (MSGnavigation as returned by GRIB is the only
* one I've actually found so far) end up returning a bounding box
Expand All @@ -180,6 +208,11 @@ public CdmTransformedGrid(GridCoordSystem coordSys) {
* It seems to be the case that the projection just doesn't work.
*/
bbox = BoundingBoxImpl.global();
}
bboxCache.put(hcsHash, bbox);
} else {
System.out.println("Obtain bounding box for grid with hash " + hcsHash + " from cache");
bbox = bboxCache.get(hcsHash);
}
}

Expand Down
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