4-bit PQ: Reading and Implementation Notes
Notes from implementing 4-bit product quantization: why it should be faster than 8-bit PQ, where the paper leaves implementation gaps, and what tradeoffs worked in practice.
systems notes / paper reading / build logs
Yang Cen
Notes on vector databases, query engines, operating systems, and the engineering details that decide whether an idea actually ships.
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Paper Reading: VBASE, Relational Queries via Relaxed Monotonicity
A reading note on VBASE and relaxed monotonicity: how ANN search can expose a streaming primitive and why that matters for filters, hybrid scoring, and vector joins.
Paper Reading: Filter Representation in Vectorized Query Execution
A reading note on bitmap and selection-vector filter representations in vectorized query engines, including when each strategy wins and why a hybrid plan can help.
Overwatch Basics: The Monitor Theory Behind Brief Black Screens
A debugging note on why a 2K 240 Hz monitor briefly blacked out when switching away from fullscreen games, and how refresh rate, bit depth, DisplayPort bandwidth, and DSC explain it.
Swap, Cache, and mmap
Notes on swap, page cache, mmap, why databases moved away from mmap as a buffer-pool replacement, and why read-only mmap can still be acceptable for immutable Milvus data.
MIT 6.824 2022 Lab 2: Raft
Notes from redoing MIT 6.824 Lab 2, covering Raft elections, log replication, persistence, log compaction, and common edge cases in the lab tests.
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