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Add release notes for PR #681 #683

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Add release notes for PR #681
r-devulap Jun 19, 2026
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Format release notes based on guidelines
r-devulap Jun 25, 2026
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23 changes: 23 additions & 0 deletions docs/release notes/4.1.0/681.performance.md
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### Faster Index Construction via Bulk Vector Serialization

**Description**
Optimized vector serialization in `MemorySegmentVectorProvider` by replacing
per-element scalar writes with bulk operations. At high core counts,
per-element scalar writes become a serialization bottleneck: multiple threads
contend on a single lock, stalling index construction and negating the benefit
of additional cores. Bulk writes eliminate that contention, restoring scaling
at large core counts.

- **`writeFloatVector`** — uses backing `float[]` with `writeFloats()` instead
of per-element `writeFloat()`
- **`writeByteSequence`** — uses backing `byte[]` with bulk `write()` instead
of per-element `writeByte()`

**How to enable**
No configuration required. The improvement is applied automatically when using
the native SIMD backend (`jvector-native`).

**Performance (AWS `x8i.24xlarge`)**
- Bulk serialization throughput: **~1.3× to 1.9×** improvement across tested vector sizes
- **openai-1536-1m** index build: ~57% faster (105.59s → 45.22s)
- **openai-3072-1m** index build: ~38% faster (164.63s → 102.75s)
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