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[3/6] Add MVV-LVA capture ordering and killer moves heuristic - #35

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[3/6] Add MVV-LVA capture ordering and killer moves heuristic#35
luccabb wants to merge 6 commits into
feature/transposition-table-boundsfrom
feature/mvv-lva-killer-moves

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@luccabb

@luccabb luccabb commented Jan 20, 2026

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Summary

  • Sort captures by MVV-LVA (Most Valuable Victim - Least Valuable Attacker)
  • Add killer moves heuristic for quiet move ordering
  • Track quiet moves that cause beta cutoffs (2 per ply)

Details

MVV-LVA Capture Ordering

Captures are now sorted by MVV-LVA score, putting the best captures first:

  • Taking a queen with a pawn is searched before taking a pawn with a queen
  • Increases the rate of beta cutoffs, reducing nodes searched

Killer Moves Heuristic

Quiet moves that caused beta cutoffs are remembered:

  • Each ply depth keeps track of 2 killer moves
  • Killers are searched immediately after captures
  • Helps find refutation moves faster in similar positions

Move Ordering Priority

  1. Captures - sorted by MVV-LVA
  2. Killer moves - quiet moves that caused cutoffs at this ply
  3. Other quiet moves - shuffled for variety

Test plan

  • All 64 unit tests pass
  • Verified killer moves are updated on beta cutoffs

🤖 Generated with Claude Code

@luccabb
luccabb force-pushed the feature/quiescence-search-improvements branch from e8b9ff6 to df8a32b Compare January 21, 2026 06:40
@luccabb
luccabb force-pushed the feature/mvv-lva-killer-moves branch from 0b53062 to 944a0e0 Compare January 21, 2026 06:40
@luccabb
luccabb force-pushed the feature/quiescence-search-improvements branch from df8a32b to bfb11c1 Compare January 21, 2026 06:44
@luccabb
luccabb force-pushed the feature/mvv-lva-killer-moves branch from 944a0e0 to f1001bf Compare January 21, 2026 06:44
@luccabb
luccabb changed the base branch from feature/quiescence-search-improvements to feature/transposition-table-bounds January 21, 2026 07:00
@luccabb luccabb changed the title [5/9] Add MVV-LVA capture ordering and killer moves heuristic [3/7] Add MVV-LVA capture ordering and killer moves heuristic Jan 21, 2026
@luccabb
luccabb force-pushed the feature/transposition-table-bounds branch from 4f7fad5 to 1c7b8d9 Compare January 21, 2026 07:33
@luccabb
luccabb force-pushed the feature/mvv-lva-killer-moves branch from f1001bf to 98ee9e1 Compare January 21, 2026 07:33
@luccabb luccabb changed the title [3/7] Add MVV-LVA capture ordering and killer moves heuristic [3/6] Add MVV-LVA capture ordering and killer moves heuristic Jan 21, 2026
@luccabb luccabb mentioned this pull request Jan 27, 2026
Merged
@luccabb luccabb closed this Jan 27, 2026
@luccabb luccabb reopened this Jan 27, 2026
@luccabb
luccabb changed the base branch from feature/transposition-table-bounds to master January 27, 2026 19:32
@luccabb
luccabb changed the base branch from master to feature/transposition-table-bounds January 27, 2026 19:34
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github-actions Bot commented Jan 27, 2026

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🔬 Stockfish Benchmark Results

vs Stockfish Skill Level 3

Metric Wins Losses Draws Total Win %
Overall 14 85 1 100 14.0%
As White 7 42 1 50 14.0%
As Black 7 43 0 50 14.0%

Non-checkmate endings:

  • Draw by 3-fold repetition: 1

vs Stockfish Skill Level 4

Metric Wins Losses Draws Total Win %
Overall 12 85 3 100 12.0%
As White 7 42 1 50 14.0%
As Black 5 43 2 50 10.0%

Non-checkmate endings:

  • Draw by insufficient mating material: 1
  • Draw by 3-fold repetition: 1

vs Stockfish Skill Level 5

Metric Wins Losses Draws Total Win %
Overall 2 97 1 100 2.0%
As White 2 47 1 50 4.0%
As Black 0 50 0 50 0%

Non-checkmate endings:

  • Draw by insufficient mating material: 1
Configuration
  • 5 chunks × 20 rounds × 3 skill levels = 300 total games
  • Each opening played with colors reversed (-repeat) for fairness
  • Moonfish: 60s per move
  • Stockfish: 60+5 time control

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🔬 Stockfish Benchmark Results

vs Stockfish Skill Level 3

Metric Wins Losses Draws Total Win %
Overall 7 91 2 100 7.0%
As White 6 42 2 50 12.0%
As Black 1 49 0 50 2.0%

Non-checkmate endings:

  • Draw by fifty moves rule: 1
  • Draw by 3-fold repetition: 1

vs Stockfish Skill Level 4

Metric Wins Losses Draws Total Win %
Overall 11 86 3 100 11.0%
As White 7 41 2 50 14.0%
As Black 4 45 1 50 8.0%

Non-checkmate endings:

  • Draw by 3-fold repetition: 2

vs Stockfish Skill Level 5

Metric Wins Losses Draws Total Win %
Overall 2 96 2 100 2.0%
As White 1 48 1 50 2.0%
As Black 1 48 1 50 2.0%

Non-checkmate endings:

  • Draw by fifty moves rule: 1
  • Draw by 3-fold repetition: 1
Configuration
  • 5 chunks × 20 rounds × 3 skill levels = 300 total games
  • Each opening played with colors reversed (-repeat) for fairness
  • Moonfish: 60s per move
  • Stockfish: 60+5 time control

luccabb and others added 6 commits February 15, 2026 22:30
@luccabb @claude
[5/9] Add MVV-LVA capture ordering and killer moves heuristic
61fda66 
Improves move ordering for better pruning:

**MVV-LVA (Most Valuable Victim - Least Valuable Attacker):**
- Sort captures by MVV-LVA score in `organize_moves()`
- Best captures (e.g., pawn takes queen) searched first
- Increases beta cutoff rate for better pruning

**Killer Moves Heuristic:**
- Track quiet moves that cause beta cutoffs (2 per ply)
- Add `killers` parameter to `organize_moves()` and `negamax()`
- Killer moves searched after captures, before other quiet moves
- Killers stored in a table indexed by ply depth

**Move Ordering Priority:**
1. Captures (sorted by MVV-LVA)
2. Killer moves (quiet moves that caused cutoffs at this ply)
3. Other quiet moves (shuffled for variety)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
@luccabb
Trigger benchmark CI
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Trigger benchmark
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Retrigger benchmark workflow
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Clean up benchmark trigger commits
e73ebd6
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luccabb force-pushed the feature/mvv-lva-killer-moves branch from 8bab1bf to e73ebd6 Compare February 16, 2026 06:34
@luccabb
luccabb force-pushed the feature/transposition-table-bounds branch from fbfac44 to 6912b81 Compare February 16, 2026 06:34
@luccabb

luccabb commented Feb 16, 2026

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/run-nps-benchmark

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github-actions Bot commented Feb 16, 2026

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⚡ NPS Benchmark Results

Metric Value
Depth 5
Positions 48
Total nodes 31699656
Total time 2965.32s
Nodes/second 10690

Node count is the primary signal — it's deterministic and catches search behavior changes. If the node count changes, the PR changed search behavior. NPS is informational only (CI runner performance varies).

Per-position breakdown 
Position  1/48: nodes=50546      time=3.69s  nps=13681
Position  2/48: nodes=3479582    time=359.44s  nps=9680
Position  3/48: nodes=6513       time=0.39s  nps=16632
Position  4/48: nodes=1514766    time=152.66s  nps=9922
Position  5/48: nodes=166003     time=18.26s  nps=9090
Position  6/48: nodes=502188     time=50.61s  nps=9923
Position  7/48: nodes=308775     time=28.84s  nps=10706
Position  8/48: nodes=286464     time=22.65s  nps=12649
Position  9/48: nodes=988200     time=78.11s  nps=12651
Position 10/48: nodes=846822     time=76.68s  nps=11043
Position 11/48: nodes=863866     time=92.90s  nps=9299
Position 12/48: nodes=648389     time=59.86s  nps=10831
Position 13/48: nodes=349739     time=30.74s  nps=11375
Position 14/48: nodes=377751     time=34.25s  nps=11028
Position 15/48: nodes=375960     time=28.70s  nps=13100
Position 16/48: nodes=833014     time=71.93s  nps=11581
Position 17/48: nodes=14449      time=0.99s  nps=14592
Position 18/48: nodes=4261       time=0.22s  nps=19804
Position 19/48: nodes=14203      time=1.09s  nps=12987
Position 20/48: nodes=39479      time=2.29s  nps=17214
Position 21/48: nodes=14797      time=0.85s  nps=17380
Position 22/48: nodes=556        time=0.03s  nps=20239
Position 23/48: nodes=4169       time=0.24s  nps=17591
Position 24/48: nodes=9828       time=0.57s  nps=17273
Position 25/48: nodes=10090      time=0.56s  nps=18095
Position 26/48: nodes=52432      time=3.79s  nps=13821
Position 27/48: nodes=128871     time=8.60s  nps=14978
Position 28/48: nodes=635469     time=52.57s  nps=12087
Position 29/48: nodes=81118      time=6.80s  nps=11924
Position 30/48: nodes=1117       time=0.07s  nps=16533
Position 31/48: nodes=943797     time=82.67s  nps=11416
Position 32/48: nodes=1307463    time=115.21s  nps=11348
Position 33/48: nodes=940285     time=115.94s  nps=8110
Position 34/48: nodes=1877969    time=203.71s  nps=9218
Position 35/48: nodes=1037438    time=83.52s  nps=12421
Position 36/48: nodes=7001400    time=677.40s  nps=10335
Position 37/48: nodes=5069942    time=430.05s  nps=11789
Position 38/48: nodes=2396       time=0.11s  nps=21984
Position 39/48: nodes=11198      time=0.40s  nps=27659
Position 40/48: nodes=12236      time=0.22s  nps=55875
Position 41/48: nodes=32999      time=2.14s  nps=15415
Position 42/48: nodes=35709      time=2.24s  nps=15928
Position 43/48: nodes=3977       time=0.20s  nps=19922
Position 44/48: nodes=58484      time=4.36s  nps=13417
Position 45/48: nodes=43661      time=3.30s  nps=13232
Position 46/48: nodes=711285     time=55.46s  nps=12824
Position 47/48: nodes=0          time=0.00s  nps=0  (terminal)
Position 48/48: nodes=0          time=0.00s  nps=0  (terminal)

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@luccabb