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Improve performance and readability of recall and precision measurements #647

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100 changes: 51 additions & 49 deletions jvector-examples/src/main/java/io/github/jbellis/jvector/example/util/AccuracyMetrics.java
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Original file line number Diff line number Diff line change
Expand Up @@ -17,11 +17,9 @@
package io.github.jbellis.jvector.example.util;

import io.github.jbellis.jvector.graph.SearchResult;

import java.util.Arrays;
import java.util.HashSet;
import java.util.List;
import java.util.stream.Collectors;
import java.util.stream.IntStream;
import java.util.Set;

/**
* Computes accuracy metrics, such as recall and mean average precision.
Expand All @@ -41,43 +39,44 @@ public static double recallFromSearchResults(List<? extends List<Integer>> gt, L
if (gt.size() != retrieved.size()) {
throw new IllegalArgumentException("Insufficient ground truth for the number of retrieved elements");
}
Long correctCount = IntStream.range(0, gt.size())
.mapToObj(i -> topKCorrect(gt.get(i), retrieved.get(i), kGT, kRetrieved))
.reduce(0L, Long::sum);

long correctCount = 0;
for (int i = 0; i < gt.size(); i++) {
correctCount += topKCorrect(gt.get(i), retrieved.get(i), kGT, kRetrieved);
}

return (double) correctCount / (kGT * gt.size());
}

private static long topKCorrect(List<Integer> gt, List<Integer> retrieved, int kGT, int kRetrieved) {
private static long topKCorrect(List<Integer> gt, SearchResult retrieved, int kGT, int kRetrieved) {
// Exception validation
var nodes = retrieved.getNodes();
if (kGT > kRetrieved) {
throw new IllegalArgumentException("kGT: " + kGT + " > kRetrieved: " + kRetrieved);
}
if (kGT > gt.size()) {
throw new IllegalArgumentException("kGT: " + kGT + " > Gt size: " + gt.size());
}
if (kRetrieved > retrieved.size()) {
throw new IllegalArgumentException("kRetrieved: " + kRetrieved + " > retrieved size: " + retrieved.size());
if (kRetrieved > nodes.length) {
throw new IllegalArgumentException("kRetrieved: " + kRetrieved + " > retrieved size: " + nodes.length);
}

var gtView = crop(gt, kGT);
var retrievedView = crop(retrieved, kRetrieved);

if (gtView.size() > retrieved.size()) {
return gtView.stream().filter(retrievedView::contains).count();
} else {
return retrievedView.stream().filter(gtView::contains).count();
// Build HashSet with explicit capacity to avoid rehashing.
// Load factor is 0.75, so sized to kGT / 0.75.
Set<Integer> gtSet = new HashSet<>((int) (kGT / 0.75f) + 1);
for (int i = 0; i < kGT; i++) {
gtSet.add(gt.get(i));
}
}

private static long topKCorrect(List<Integer> gt, SearchResult retrieved, int kGT, int kRetrieved) {
var temp = Arrays.stream(retrieved.getNodes()).mapToInt(nodeScore -> nodeScore.node)
.boxed()
.collect(Collectors.toList());
return topKCorrect(gt, temp, kGT, kRetrieved);
}
// Manual primitive loop for speed (no Stream setup).
int hits = 0;
for (int i = 0; i < kRetrieved; i++) {
if (gtSet.contains(nodes[i].node)) {
hits++;
Comment on lines +74 to +75
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@ashkrisk ashkrisk Mar 20, 2026

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Wondering if we should handle dupes in retrieved like we do in case of averagePrecisionAtK. That said, the earlier version of this function didn't handle duplicates either.

}
}

private static List<Integer> crop(List<Integer> list, int k) {
int count = Math.min(list.size(), k);
return list.subList(0, count);
return hits;
}

/**
Expand All @@ -89,33 +88,34 @@ private static List<Integer> crop(List<Integer> list, int k) {
* @return the average precision
*/
public static double averagePrecisionAtK(List<Integer> gt, SearchResult retrieved, int k) {
var retrievedTemp = Arrays.stream(retrieved.getNodes()).mapToInt(nodeScore -> nodeScore.node)
.boxed()
.collect(Collectors.toList());

var nodes = retrieved.getNodes();
if (k > gt.size()) {
throw new IllegalArgumentException("k: " + k + " > Gt size: " + gt.size());
}
if (k > retrievedTemp.size()) {
throw new IllegalArgumentException("k: " + k + " > retrieved size: " + retrievedTemp.size());
if (k > nodes.length) {
throw new IllegalArgumentException("k: " + k + " > retrieved size: " + nodes.length);
}

var gtView = crop(gt, k);
var retrievedView = crop(retrievedTemp, k);
// Sized hashset used for performance.
Set<Integer> gtSet = new HashSet<>((int) (k / 0.75f) + 1);
for (int i = 0; i < k; i++) {
gtSet.add(gt.get(i));
}

double score = 0.;
int num_hits = 0;
int i = 0;
// Handles potential duplicates in O(1).
Set<Integer> seen = new HashSet<>((int) (k / 0.75f) + 1);

for (var p : retrievedView) {
if (gtView.contains(p) && !retrievedView.subList(0, i).contains(p)) {
num_hits += 1;
score += num_hits / (i + 1.0);
double score = 0.;
int hits = 0;
for (int i = 0; i < k; i++) {
int p = nodes[i].node;
if (gtSet.contains(p) && seen.add(p)) {
hits++;
score += (double) hits / (i + 1);
}
i++;
}

return score / gtView.size();
return score / k;
}

/**
Expand All @@ -130,10 +130,12 @@ public static double meanAveragePrecisionAtK(List<? extends List<Integer>> gt, L
if (gt.size() != retrieved.size()) {
throw new IllegalArgumentException("Insufficient ground truth for the number of retrieved elements");
}
Double apk = IntStream.range(0, gt.size())
.mapToObj(i -> averagePrecisionAtK(gt.get(i), retrieved.get(i), k))
.reduce(0., Double::sum);
return apk / gt.size();
}

double totalAp = 0;
for (int i = 0; i < gt.size(); i++) {
totalAp += averagePrecisionAtK(gt.get(i), retrieved.get(i), k);
}

return totalAp / gt.size();
}
}
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