HNSW Stress Tests

Stress tests for the Hierarchical Navigable Small World (HNSW) index, targeting 1M vector scale.

Test Suite

Results

Running

# Run all HNSW stress tests
cargo test --release -p stress_tests --test hnsw_stress -- --ignored --nocapture

# Run specific test
cargo test --release -p stress_tests stress_hnsw_1m_vectors -- --ignored --nocapture

1M Vector Index Build

Tests building an HNSW index with 1 million 128-dimensional vectors.

What it validates:

• Memory efficiency at scale
• Index build time scalability
• Search accuracy after large insertions

Expected behavior:

• Linear memory growth with vector count
• Sub-linear search time (O(log n))
• Recall@10 > 95%

Concurrent Index Build

Tests building an HNSW index with 16 concurrent writer threads.

What it validates:

• Thread-safety of HNSW insert operations
• Performance under contention
• Correctness with concurrent modifications

Expected behavior:

• All inserted vectors are findable
• No panics or data races
• Throughput scales with thread count (with diminishing returns)

Search During Insert

Tests searching the index while new vectors are being inserted concurrently.

What it validates:

• Read/write concurrency safety
• Search accuracy with ongoing modifications
• Latency stability under load

Expected behavior:

• Searches return valid results
• No stale or corrupted results
• Latency remains bounded

Recall Under Load

Tests search recall accuracy under sustained concurrent load.

What it validates:

• HNSW recall guarantees under stress
• Accuracy with high query volume
• Configuration impact on recall

Expected behavior:

• Average recall@10 > 95%
• Minimum recall@10 > 90%
• High_recall config > default config recall

Performance Tuning

HNSW Configuration Impact

Scaling Recommendations