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Optimize and simplify tile retention logic (mapbox#6995)
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* clean up tile retention logic a bit

* simplify retention logic further

* simplify raster tile retaining logic

* avoid delete when retaining child tiles

* much faster children retention logic

* simplify parent tile retention

* address PR feedback

* clear up source cache comments
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@mourner @pirxpilot
mourner authored and pirxpilot committed Jun 18, 2019
1 parent d7111ef commit 3553202
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Showing 3 changed files with 126 additions and 140 deletions.
2 changes: 1 addition & 1 deletion src/render/draw_raster.js
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Original file line number Diff line number Diff line change
Expand Up @@ -47,7 +47,7 @@ function drawRaster(painter, sourceCache, layer, coords) {

gl.uniformMatrix4fv(program.uniforms.u_matrix, false, posMatrix);

const parentTile = sourceCache.findLoadedParent(coord, 0, {}),
const parentTile = sourceCache.findLoadedParent(coord, 0),
fade = getFadeValues(tile, parentTile, sourceCache, layer, painter.transform);

let parentScaleBy, parentTL;
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246 changes: 121 additions & 125 deletions src/source/source_cache.js
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Original file line number Diff line number Diff line change
Expand Up @@ -166,7 +166,7 @@ class SourceCache extends Evented {
}

hasRenderableParent(tileID) {
const parentTile = this.findLoadedParent(tileID, 0, {});
const parentTile = this.findLoadedParent(tileID, 0);
if (parentTile) {
return this._isIdRenderable(parentTile.tileID.key);
}
Expand Down Expand Up @@ -298,59 +298,59 @@ class SourceCache extends Evented {
}

/**
* Recursively find children of the given tile (up to maxCoveringZoom) that are already loaded;
* adds found tiles to retain object; returns true if any child is found.
* For a given set of tiles, retain children that are loaded and have a zoom
* between `zoom` (exclusive) and `maxCoveringZoom` (inclusive)
*/
_findLoadedChildren(tileID, maxCoveringZoom, retain) {
let found = false;

_retainLoadedChildren(idealTiles, zoom, maxCoveringZoom, retain) {
for (const id in this._tiles) {
let tile = this._tiles[id];

// only consider renderable tiles on higher zoom levels (up to maxCoveringZoom)
if (retain[id] || !tile.hasData() || tile.tileID.overscaledZ <= tileID.overscaledZ || tile.tileID.overscaledZ > maxCoveringZoom) continue;

// disregard tiles that are not descendants of the given tile coordinate
const z2 = Math.pow(2, tile.tileID.canonical.z - tileID.canonical.z);
if (Math.floor(tile.tileID.canonical.x / z2) !== tileID.canonical.x ||
Math.floor(tile.tileID.canonical.y / z2) !== tileID.canonical.y)
continue;
// only consider renderable tiles up to maxCoveringZoom
if (retain[id] ||
!tile.hasData() ||
tile.tileID.overscaledZ <= zoom ||
tile.tileID.overscaledZ > maxCoveringZoom
) continue;

// found loaded child
retain[id] = tile.tileID;
found = true;
// loop through parents and retain the topmost loaded one if found
let topmostLoadedID = tile.tileID;
while (tile && tile.tileID.overscaledZ > zoom + 1) {
const parentID = tile.tileID.scaledTo(tile.tileID.overscaledZ - 1);

// loop through parents; retain the topmost loaded one if found
while (tile && tile.tileID.overscaledZ - 1 > tileID.overscaledZ) {
const parent = tile.tileID.scaledTo(tile.tileID.overscaledZ - 1);
if (!parent) break;
tile = this._tiles[parentID.key];

tile = this._tiles[parent.key];
if (tile && tile.hasData()) {
delete retain[id];
retain[parent.key] = parent;
topmostLoadedID = parentID;
}
}

// loop through ancestors of the topmost loaded child to see if there's one that needed it
let tileID = topmostLoadedID;
while (tileID.overscaledZ > zoom) {
tileID = tileID.scaledTo(tileID.overscaledZ - 1);

if (idealTiles[tileID.key]) {
// found a parent that needed a loaded child; retain that child
retain[topmostLoadedID.key] = topmostLoadedID;
break;
}
}
}
return found;
}

/**
* Find a loaded parent of the given tile (up to minCoveringZoom);
* adds the found tile to retain object and returns the tile if found
* Find a loaded parent of the given tile (up to minCoveringZoom)
*/
findLoadedParent(tileID, minCoveringZoom, retain) {
findLoadedParent(tileID, minCoveringZoom) {
for (let z = tileID.overscaledZ - 1; z >= minCoveringZoom; z--) {
const parent = tileID.scaledTo(z);
if (!parent) return;
const id = String(parent.key);
const tile = this._tiles[id];
if (tile && tile.hasData()) {
retain[id] = parent;
return tile;
}
if (this._cache.has(parent)) {
retain[id] = parent;
return this._cache.get(parent);
}
}
Expand Down Expand Up @@ -464,52 +464,48 @@ class SourceCache extends Evented {
// parent or child tiles that are *already* loaded.
const retain = this._updateRetainedTiles(idealTileIDs, zoom);

const parentsForFading = {};

if (isRasterType(this._source.type)) {
const parentsForFading = {};
const fadingTiles = {};
const ids = Object.keys(retain);
for (let k = 0; k < ids.length; k++) {
const id = ids[k];
for (const id of ids) {
const tileID = retain[id];
assert(tileID.key === +id);

const tile = this._tiles[id];
if (!tile) continue;

// If the drawRasterTile has never seen this tile, then
// tile.fadeEndTime may be unset. In that case, or if
// fadeEndTime is in the future, then this tile is still
// fading in. Find tiles to cross-fade with it.
if (typeof tile.fadeEndTime === 'undefined' || tile.fadeEndTime >= browser.now()) {
if (this._findLoadedChildren(tileID, maxCoveringZoom, retain)) {
retain[id] = tileID;
}
const parentTile = this.findLoadedParent(tileID, minCoveringZoom, parentsForFading);
if (parentTile) {
this._addTile(parentTile.tileID);
}
if (!tile || tile.fadeEndTime && tile.fadeEndTime <= browser.now()) continue;

// if the tile is loaded but still fading in, find parents to cross-fade with it
const parentTile = this.findLoadedParent(tileID, minCoveringZoom);
if (parentTile) {
this._addTile(parentTile.tileID);
parentsForFading[parentTile.tileID.key] = parentTile.tileID;
}

fadingTiles[id] = tileID;
}
}

let fadedParent;
for (fadedParent in parentsForFading) {
if (!retain[fadedParent]) {
// If a tile is only needed for fading, mark it as covered so that it isn't rendered on it's own.
this._coveredTiles[fadedParent] = true;
// for tiles that are still fading in, also find children to cross-fade with
this._retainLoadedChildren(fadingTiles, zoom, maxCoveringZoom, retain);

for (const id in parentsForFading) {
if (!retain[id]) {
// If a tile is only needed for fading, mark it as covered so that it isn't rendered on it's own.
this._coveredTiles[id] = true;
retain[id] = parentsForFading[id];
}
}
}
for (fadedParent in parentsForFading) {
retain[fadedParent] = parentsForFading[fadedParent];
}

for (const retainedId in retain) {
// Make sure retained tiles always clear any existing fade holds
// so that if they're removed again their fade timer starts fresh.
this._tiles[retainedId].clearFadeHold();
}

// Remove the tiles we don't need anymore.
const remove = keysDifference(this._tiles, retain);
for (let i = 0; i < remove.length; i++) {
const tileID = remove[i];
for (const tileID of remove) {
const tile = this._tiles[tileID];
if (tile.hasSymbolBuckets && !tile.holdingForFade()) {
tile.setHoldDuration(this.map._fadeDuration);
Expand All @@ -533,74 +529,74 @@ class SourceCache extends Evented {
const minCoveringZoom = Math.max(zoom - SourceCache.maxOverzooming, this._source.minzoom);
const maxCoveringZoom = Math.max(zoom + SourceCache.maxUnderzooming, this._source.minzoom);

for (let i = 0; i < idealTileIDs.length; i++) {
const tileID = idealTileIDs[i];
let tile = this._addTile(tileID);
let parentWasRequested = false;
if (tile.hasData()) {
retain[tileID.key] = tileID;
} else {
// The tile we require is not yet loaded or does not exist.
// We are now attempting to load child and parent tiles.

// As we descend up and down the tile pyramid of the ideal tile, we check whether the parent
// tile has been previously requested (and errored in this case due to the previous conditional)
// in order to determine if we need to request its parent.
parentWasRequested = tile.wasRequested();

// The tile isn't loaded yet, but retain it anyway because it's an ideal tile.
retain[tileID.key] = tileID;
let covered = true;
const overscaledZ = zoom + 1;
if (overscaledZ > this._source.maxzoom) {
// We're looking for an overzoomed child tile.
const childCoord = tileID.children(this._source.maxzoom)[0];
const childTile = this.getTile(childCoord);
if (!!childTile && childTile.hasData()) {
retain[childCoord.key] = childCoord;
} else {
covered = false;
}
} else {
this._findLoadedChildren(tileID, maxCoveringZoom, retain);
// check if all 4 immediate children are loaded (i.e. the missing ideal tile is covered)
const children = tileID.children(this._source.maxzoom);
for (let j = 0; j < children.length; j++) {
if (!retain[children[j].key]) {
covered = false;
break;
}
}
const missingTiles = {};
for (const tileID of idealTileIDs) {
const tile = this._addTile(tileID);

// retain the tile even if it's not loaded because it's an ideal tile.
retain[tileID.key] = tileID;

if (tile.hasData()) continue;

if (zoom < this._source.maxzoom) {
// save missing tiles that potentially have loaded children
missingTiles[tileID.key] = tileID;
}
}

// retain any loaded children of ideal tiles up to maxCoveringZoom
this._retainLoadedChildren(missingTiles, zoom, maxCoveringZoom, retain);

for (const tileID of idealTileIDs) {
let tile = this._tiles[tileID.key];

if (tile.hasData()) continue;

// The tile we require is not yet loaded or does not exist;
// Attempt to find children that fully cover it.

if (zoom + 1 > this._source.maxzoom) {
// We're looking for an overzoomed child tile.
const childCoord = tileID.children(this._source.maxzoom)[0];
const childTile = this.getTile(childCoord);
if (!!childTile && childTile.hasData()) {
retain[childCoord.key] = childCoord;
continue; // tile is covered by overzoomed child
}
} else {
// check if all 4 immediate children are loaded (i.e. the missing ideal tile is covered)
const children = tileID.children(this._source.maxzoom);

if (retain[children[0].key] &&
retain[children[1].key] &&
retain[children[2].key] &&
retain[children[3].key]) continue; // tile is covered by children
}

// We couldn't find child tiles that entirely cover the ideal tile; look for parents now.

if (!covered) {

// We couldn't find child tiles that entirely cover the ideal tile.
for (let overscaledZ = tileID.overscaledZ - 1; overscaledZ >= minCoveringZoom; --overscaledZ) {

const parentId = tileID.scaledTo(overscaledZ);
if (checked[parentId.key]) {
// Break parent tile ascent, this route has been previously checked by another child.
break;
} else {
checked[parentId.key] = true;
}

tile = this.getTile(parentId);
if (!tile && parentWasRequested) {
tile = this._addTile(parentId);
}

if (tile) {
retain[parentId.key] = parentId;
// Save the current values, since they're the parent of the next iteration
// of the parent tile ascent loop.
parentWasRequested = tile.wasRequested();
if (tile.hasData()) {
break;
}
}
}
// As we ascend up the tile pyramid of the ideal tile, we check whether the parent
// tile has been previously requested (and errored because we only loop over tiles with no data)
// in order to determine if we need to request its parent.
let parentWasRequested = tile.wasRequested();

for (let overscaledZ = tileID.overscaledZ - 1; overscaledZ >= minCoveringZoom; --overscaledZ) {
const parentId = tileID.scaledTo(overscaledZ);

// Break parent tile ascent if this route has been previously checked by another child.
if (checked[parentId.key]) break;
checked[parentId.key] = true;

tile = this.getTile(parentId);
if (!tile && parentWasRequested) {
tile = this._addTile(parentId);
}
if (tile) {
retain[parentId.key] = parentId;
// Save the current values, since they're the parent of the next iteration
// of the parent tile ascent loop.
parentWasRequested = tile.wasRequested();
if (tile.hasData()) break;
}
}
}
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18 changes: 4 additions & 14 deletions test/unit/source/source_cache.test.js
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Original file line number Diff line number Diff line change
Expand Up @@ -1413,13 +1413,8 @@ test('SourceCache#findLoadedParent', (t) => {

sourceCache._tiles[tile.tileID.key] = tile;

const retain = {};
const expectedRetain = {};
expectedRetain[tile.tileID.key] = tile.tileID;

t.equal(sourceCache.findLoadedParent(new OverscaledTileID(2, 0, 2, 3, 3), 0, retain), undefined);
t.deepEqual(sourceCache.findLoadedParent(new OverscaledTileID(2, 0, 2, 0, 0), 0, retain), tile);
t.deepEqual(retain, expectedRetain);
t.equal(sourceCache.findLoadedParent(new OverscaledTileID(2, 0, 2, 3, 3), 0), undefined);
t.deepEqual(sourceCache.findLoadedParent(new OverscaledTileID(2, 0, 2, 0, 0), 0), tile);
t.end();
});

Expand All @@ -1434,13 +1429,8 @@ test('SourceCache#findLoadedParent', (t) => {
const tile = new Tile(new OverscaledTileID(1, 0, 1, 0, 0), 512, 22);
sourceCache._cache.add(tile.tileID, tile);

const retain = {};
const expectedRetain = {};
expectedRetain[tile.tileID.key] = tile.tileID;

t.equal(sourceCache.findLoadedParent(new OverscaledTileID(2, 0, 2, 3, 3), 0, retain), undefined);
t.equal(sourceCache.findLoadedParent(new OverscaledTileID(2, 0, 2, 0, 0), 0, retain), tile);
t.deepEqual(retain, expectedRetain);
t.equal(sourceCache.findLoadedParent(new OverscaledTileID(2, 0, 2, 3, 3), 0), undefined);
t.equal(sourceCache.findLoadedParent(new OverscaledTileID(2, 0, 2, 0, 0), 0), tile);
t.equal(sourceCache._cache.order.length, 1);

t.end();
Expand Down

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