Question 1

RoaringBitmap vs Java BitSet when to use which

Accepted Answer

Use RoaringBitmap for large, sparse integer sets where memory efficiency and fast set operations are critical; BitSet is better for small, dense ranges under 128 values due to its simplicity and lower overhead. Always benchmark with your specific data to confirm performance gains.

Question 2

How to serialize RoaringBitmap to a file safely

Accepted Answer

Serialize using DataOutputStream and deserialize with DataInputStream, then call validate() to check for corruption. For untrusted sources, add hashing for tamper detection, as recommended in the README examples to ensure data integrity.

Question 3

Roaring64NavigableMap or Roaring64Bitmap which one is faster

Accepted Answer

Roaring64NavigableMap uses a red-black tree and is more established, while Roaring64Bitmap uses an ART data structure for potentially better performance with 48-bit keys. Test both with your dataset, as the README notes different underlying structures but doesn't provide clear benchmarks.

Question 4

Does RoaringBitmap handle negative integers correctly

Accepted Answer

Yes, it treats integers as unsigned using Integer.compareUnsigned, so negative values are interpreted as high positive numbers in the range. Use Integer.toUnsignedLong for proper interpretation, as explained in the Unsigned Integers section.

Question 5

How to optimize RoaringBitmap for consecutive values

Accepted Answer

Call runOptimize() after building the bitmap to compress runs of consecutive values into run-length encoding, which can reduce serialized size. However, this may slightly impact some operation speeds, so profile if needed.

Question 6

Is RoaringBitmap thread safe for multiple readers

Accepted Answer

Only immutable bitmaps are thread-safe for concurrent reads; mutable bitmaps require external synchronization. The README states that ImmutableRoaringBitmap instances can be accessed from multiple threads if used via the ImmutableBitmapDataProvider interface.

RoaringBitmap

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