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Reduce the memory allocation during search with mutable IndexedScore. #8225

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Reduce the memory allocation during search with mutable IndexedScore. #8225

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1 change: 1 addition & 0 deletions CHANGELOG.md
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Expand Up @@ -2,6 +2,7 @@ Important changes to data models, configuration, and migrations between each
AppEngine version, listed here to ease deployment and troubleshooting.

## Next Release (replace with git tag when deployed)
* `search` uses the `IndexedScore` to reduce memory allocations.

## `20241031t095600-all`
* Bumped runtimeVersion to `2024.10.29`.
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83 changes: 37 additions & 46 deletions app/lib/search/mem_index.dart
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Expand Up @@ -311,32 +311,28 @@ class InMemoryPackageIndex {
// We cannot update the main `packages` variable yet, as the dartdoc API
// symbols are added on top of the core results, and `packages` is used
// there too.
final coreScores = <Score>[];
var wordScopedPackages = packages;
final coreScores = IndexedScore(_packageNameIndex._packageNames);
for (var i = 0; i < _documents.length; i++) {
if (packages.contains(_documents[i].package)) {
coreScores.setValue(i, 1.0);
}
}

for (final word in words) {
final nameScore = _packageNameIndex.searchWord(word,
filterOnPackages: wordScopedPackages);
if (includeNameMatches && _documentsByName.containsKey(word)) {
nameMatches ??= <String>{};
nameMatches.add(word);
}

final descr = _descrIndex
.searchWords([word], weight: 0.90, limitToIds: wordScopedPackages);
final readme = _readmeIndex
.searchWords([word], weight: 0.75, limitToIds: wordScopedPackages);
final score = Score.max([nameScore, descr, readme]);
coreScores.add(score);
// don't update if the query is single-word
if (words.length > 1) {
wordScopedPackages = score.keys.toSet();
if (wordScopedPackages.isEmpty) {
break;
}
}
final wordScore =
_packageNameIndex.searchWord(word, filterOnNonZeros: coreScores);
_descrIndex.searchAndAccumulate(word,
weight: 0.90.toDouble(), score: wordScore);
_readmeIndex.searchAndAccumulate(word,
weight: 0.75.toDouble(), score: wordScore);
coreScores.multiplyAllFrom(wordScore);
}

final core = Score.multiply(coreScores);
final core = coreScores.toScore();

var symbolPages = Score.empty;
if (!checkAborted()) {
Expand Down Expand Up @@ -502,16 +498,13 @@ class _TextResults {
@visibleForTesting
class PackageNameIndex {
final List<String> _packageNames;
late final Map<String, _PkgNameData> _data;
late final List<_PkgNameData> _data;

PackageNameIndex(this._packageNames) {
_data = Map.fromEntries(_packageNames.map((package) {
_data = _packageNames.map((package) {
final collapsed = _collapseName(package);
return MapEntry(
package,
_PkgNameData(collapsed, trigrams(collapsed).toSet()),
);
}));
return _PkgNameData(collapsed, trigrams(collapsed).toSet());
}).toList();
}

/// Maps package name to a reduced form of the name:
Expand All @@ -522,45 +515,43 @@ class PackageNameIndex {
/// Search [text] and return the matching packages with scores.
@visibleForTesting
Score search(String text) {
Score? score;
IndexedScore? score;
for (final w in splitForQuery(text)) {
final s = searchWord(w, filterOnPackages: score?.keys);
final s = searchWord(w, filterOnNonZeros: score);
if (score == null) {
score = s;
} else {
// Note: on one hand, it is inefficient to multiply the [Score] on each
// iteration. However, (1) this is only happening in test, (2) it may be
// better for the next iteration to work on a more limited `filterOnPackages`,
// and (3) it will be updated to a more efficient in-place update (#8225).
score = Score.multiply([score, s]);
score.multiplyAllFrom(s);
}
}
return score ?? Score.empty;
return score?.toScore() ?? Score.empty;

}

/// Search using the parsed [word] and return the matching packages with scores
/// as a new [Score] instance.
/// as a new [IndexedScore] instance.
///
/// When [filterOnPackages] is present, only the names present are evaluated.
Score searchWord(
/// When [filterOnNonZeros] is present, only the indexes with an already
/// non-zero value are evaluated.
IndexedScore searchWord(
String word, {
Iterable<String>? filterOnPackages,
IndexedScore? filterOnNonZeros,
}) {
final pkgNamesToCheck = filterOnPackages ?? _packageNames;
final values = <String, double>{};
final score = IndexedScore(_packageNames);
final singularWord = word.length <= 3 || !word.endsWith('s')
? word
: word.substring(0, word.length - 1);
final collapsedWord = _collapseName(singularWord);
final parts =
collapsedWord.length <= 3 ? [collapsedWord] : trigrams(collapsedWord);
for (final pkg in pkgNamesToCheck) {
final entry = _data[pkg];
if (entry == null) {
for (var i = 0; i < _data.length; i++) {
if (filterOnNonZeros?.isNotPositive(i) ?? false) {
continue;
}

final entry = _data[i];
if (entry.collapsed.contains(collapsedWord)) {
values[pkg] = 1.0;
score.setValue(i, 1.0);
continue;
}
var matched = 0;
Expand All @@ -574,11 +565,11 @@ class PackageNameIndex {
if (matched > 0) {
final v = matched / parts.length;
if (v >= 0.5) {
values[pkg] = v;
score.setValue(i, v);
}
}
}
return Score(values);
return score;
}
}

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113 changes: 69 additions & 44 deletions app/lib/search/token_index.dart
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Expand Up @@ -206,37 +206,22 @@ class TokenIndex {
return tokenMatch;
}

/// Returns an {id: score} map of the documents stored in the [TokenIndex].
/// The tokens in [tokenMatch] will be used to calculate a weighted sum of scores.
///
/// When [limitToIds] is specified, the result will contain only the set of
/// identifiers in it.
Map<String, double> _scoreDocs(TokenMatch tokenMatch,
{double weight = 1.0, Set<String>? limitToIds}) {
// Summarize the scores for the documents.
final docScores = List<double>.filled(_length, 0.0);
/// Searches the index with [word] and stores the results in [score], using
/// accumulation operation on the already existing values.
void searchAndAccumulate(
String word, {
double weight = 1.0,
required IndexedScore score,
}) {
assert(score.length == _length);
final tokenMatch = lookupTokens(word);
for (final token in tokenMatch.tokens) {
final docWeights = _inverseIds[token]!;
for (final e in docWeights.entries) {
final i = e.key;
docScores[i] = math.max(docScores[i], tokenMatch[token]! * e.value);
final matchWeight = tokenMatch[token]!;
final tokenWeight = _inverseIds[token]!;
for (final e in tokenWeight.entries) {
score.setValueMaxOf(e.key, matchWeight * e.value * weight);
}
}

final result = <String, double>{};
// post-process match weights
for (var i = 0; i < _length; i++) {
final id = _ids[i];
final w = docScores[i];
if (w <= 0.0) {
continue;
}
if (limitToIds != null && !limitToIds.contains(id)) {
continue;
}
result[id] = w * weight;
}
return result;
}

/// Search the index for [text], with a (term-match / document coverage percent)
Expand All @@ -248,24 +233,64 @@ class TokenIndex {

/// Search the index for [words], with a (term-match / document coverage percent)
/// scoring.
Score searchWords(List<String> words,
{double weight = 1.0, Set<String>? limitToIds}) {
if (limitToIds != null && limitToIds.isEmpty) {
return Score.empty;
}
final scores = <Score>[];
Score searchWords(List<String> words, {double weight = 1.0}) {
IndexedScore? score;
for (final w in words) {
final tokens = lookupTokens(w);
final values = _scoreDocs(
tokens,
weight: weight,
limitToIds: limitToIds,
);
if (values.isEmpty) {
return Score.empty;
final s = IndexedScore(_ids);
searchAndAccumulate(w, score: s, weight: weight);
if (score == null) {
score = s;
// reset weight
weight = 1.0;
} else {
score.multiplyAllFrom(s);
}
}
return score?.toScore() ?? Score.empty;
}
}

/// Mutable score list that can accessed via integer index.
class IndexedScore {
final List<String> _keys;
final List<double> _values;

IndexedScore._(this._keys, this._values);

factory IndexedScore(List<String> keys) =>
IndexedScore._(keys, List<double>.filled(keys.length, 0.0));

late final length = _values.length;

bool isNotPositive(int index) {
return _values[index] <= 0.0;
}

void setValue(int index, double value) {
_values[index] = value;
}

void setValueMaxOf(int index, double value) {
_values[index] = math.max(_values[index], value);
}

void multiplyAllFrom(IndexedScore other) {
assert(other._values.length == _values.length);
for (var i = 0; i < _values.length; i++) {
if (_values[i] == 0.0) continue;
final v = other._values[i];
_values[i] = v == 0.0 ? 0.0 : _values[i] * v;
}
}

Score toScore() {
final map = <String, double>{};
for (var i = 0; i < _values.length; i++) {
final v = _values[i];
if (v > 0.0) {
map[_keys[i]] = v;
}
scores.add(Score(values));
}
return Score.multiply(scores);
return Score._(map);
}
}
4 changes: 2 additions & 2 deletions app/test/search/api_doc_page_test.dart
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Expand Up @@ -99,7 +99,7 @@ void main() {
'packageHits': [
{
'package': 'foo',
'score': closeTo(0.18, 0.01), // find WebPageGenerator
'score': closeTo(0.26, 0.01), // find WebPageGenerator
'apiPages': [
{'path': 'generator.html'},
],
Expand All @@ -119,7 +119,7 @@ void main() {
'packageHits': [
{
'package': 'foo',
'score': closeTo(0.11, 0.01), // find WebPageGenerator
'score': closeTo(0.15, 0.01), // find WebPageGenerator
'apiPages': [
{'path': 'generator.html'},
],
Expand Down
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