[juchen-ms (partychen)]

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• Does this PR modify any existing APIs?
• Is the change to the API backwards compatible?
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Reference Issues/PRs

What does this implement/fix? Briefly explain your changes.

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MinMax MaxSim benchmark results

Timings are microseconds per MaxSim call (lower is better). The comparison workload uses 32 query vectors, 128 document vectors, and 128 dimensions, with independent query/document quantization widths of 1, 2, 4, and 8 bits.

• Pairwise / V3 / V4: measured natively on an Intel Xeon Platinum 8370C. Each configuration uses 100 measurements of 200 calls; the reported time is the minimum batch latency divided by 200. Data generation, quantization, query packing, and score-buffer allocation are outside the timed region. Repeated calls reuse the same data; document decoding and scratch allocation inside the matrix kernel remain included.
• Pairwise is the existing MinMaxIP query/document double loop, compiled for x86-64-v3—not the scalar/reference factory backend. A dash means the existing pairwise API does not support that ordered bit-width combination; no substitute implementation was measured.
• NEON: timings supplied by the author. The ARM CPU model and measurement setup have not been recorded here. Pairwise / NEON is a cross-platform timing ratio against the x86 pairwise baseline, not a same-machine SIMD speedup. V3/V4 ratios use the same-machine pairwise baseline.

Query bit	Document bit	Pairwise	V3	V4	NEON	Pairwise / V3	Pairwise / V4	Pairwise / NEON
1	1	15.560	8.065	5.445	5.775	1.93x	2.86x	2.69x
1	2	—	7.650	5.355	4.976	—	—	—
1	4	—	8.330	5.425	5.034	—	—	—
1	8	—	9.715	9.380	4.878	—	—	—
2	1	—	8.040	5.430	5.775	—	—	—
2	2	46.255	7.660	5.340	4.989	6.04x	8.66x	9.27x
2	4	—	8.350	5.470	5.036	—	—	—
2	8	—	9.625	9.375	4.878	—	—	—
4	1	—	8.095	5.430	5.784	—	—	—
4	2	—	7.640	5.340	4.972	—	—	—
4	4	47.215	8.260	5.135	5.042	5.72x	9.19x	9.36x
4	8	—	9.785	9.505	4.876	—	—	—
8	1	31.860	8.115	5.260	5.776	3.93x	6.06x	5.52x
8	2	53.925	7.660	5.270	4.977	7.04x	10.23x	10.83x
8	4	39.695	8.340	5.430	5.043	4.76x	7.31x	7.87x
8	8	48.460	9.680	8.905	4.881	5.01x	5.44x	9.93x

These results characterize repeated scoring of warm data at the stated fixed workload; they do not measure end-to-end search, cold-cache behavior, quantization accuracy, or query preparation cost.

[Codecov Comments Bot (codecov-commenter)]

Codecov Report

❌ Patch coverage is 97.94521% with 9 lines in your changes missing coverage. Please review.
✅ Project coverage is 91.08%. Comparing base (8a9ff2d) to head (f484895).
⚠️ Report is 4 commits behind head on main.

Files with missing lines	Patch %	Lines
diskann-quantization/src/minmax/multi/factory.rs	98.00%	6 Missing ⚠️
diskann-quantization/src/minmax/multi/reference.rs	92.30%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1509      +/-   ##
==========================================
- Coverage   92.16%   91.08%   -1.09%     
==========================================
  Files         592      596       +4     
  Lines      123582   124095     +513     
==========================================
- Hits       113901   113031     -870     
- Misses       9681    11064    +1383     

Flag	Coverage Δ
miri	91.08% <97.94%> (-1.09%)	⬇️
unittests	90.79% <97.92%> (-1.33%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
..._kernels/maxsim/packed_minmax_x_unpacked_minmax.rs	94.63% <100.00%> (-3.56%)	⬇️
diskann-quantization/src/minmax/multi/kernel.rs	100.00% <100.00%> (ø)
diskann-quantization/src/minmax/multi/meta.rs	100.00% <100.00%> (ø)
diskann-quantization/src/minmax/multi/prepared.rs	100.00% <100.00%> (ø)
...-quantization/src/multi_vector/distance/factory.rs	77.51% <ø> (ø)
diskann-quantization/src/minmax/multi/reference.rs	92.30% <92.30%> (ø)
diskann-quantization/src/minmax/multi/factory.rs	98.00% <98.00%> (ø)

... and 64 files with indirect coverage changes

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