Comment on: Experiment: Fused Q·Centroid compressed attention for turbo3 decode

## 4-Entry Magnitude LUT + Branchless Sign: BEST M2 RESULT **Approach:** 4-entry constant half magnitude LUT (0.021-0.190) + XOR trick for reversed magnitude order + branchless sign multiply. Only 4 possible constant addresses per lookup instead of 8. ### M2 Pro decode improvement: | Depth | q8_0 | Main (8-LUT) | 4-mag LUT | vs Main | vs q8_0 | |-------|------|-------------|-----------|---------|---------| | short | 32.5 | 22.9 | 23.8 | +3.9% | 0.732x | | 8K | 21.9 | 10.95 | 15.1 | **+37.9%** | 0.689x | | 16K | 17.2 | 8.0 | 11.6 | **+45.0%** | 0.674x | ### M5 Max (no regression): | Depth | Main | 4-mag LUT | Delta | |-------|------|-----------|-------| | short | 77.4 | 75.7 | -2.2% | PPL: 6.1756 (unchanged). ### Summary +38-45% decode improvement on M2 Pro at long context. The ratio vs q8_0 improved from 0.45-0.50x to 0.67-0.73x. The cliff is much less severe. Minor regression on M5 (-2.2%) from the extra ALU (XOR + sign multiply). Could use the auto-detection to use 4-mag on ...