leerho commented on code in PR #676:
URL: https://github.com/apache/datasketches-java/pull/676#discussion_r2229748283
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src/main/java/org/apache/datasketches/count/CountMinSketch.java:
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@@ -57,30 +65,59 @@ int mask() {
* @param seed The base hash seed
*/
CountMinSketch(final byte numHashes, final int numBuckets, final long seed) {
- numHashes_ = numHashes;
- numBuckets_ = numBuckets;
- seed_ = seed;
- hashSeeds_ = new long[numHashes];
- sketchArray_ = new long[numHashes * numBuckets];
- totalWeight_ = 0;
+ // Validate numHashes
+ if (numHashes <= 0) {
+ throw new SketchesArgumentException("Number of hash functions must be
positive, got: " + numHashes);
+ }
+ // Validate numBuckets with clear mathematical justification
+ if (numBuckets <= 0) {
+ throw new SketchesArgumentException("Number of buckets must be positive,
got: " + numBuckets);
+ }
if (numBuckets < 3) {
- throw new SketchesArgumentException("Using fewer than 3 buckets incurs
relative error greater than 1.");
+ throw new SketchesArgumentException("Number of buckets must be at least
3 to ensure relative error ≤ 1.0. " +
+ "With " + numBuckets + " buckets, relative error would be " +
String.format("%.3f", Math.exp(1.0) / numBuckets));
Review Comment:
The "+" should be at the beginning of the next line.
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