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Mantis

9221218app

Chess Engine written in Odin

5Open repo
No license · updated 2 weeks ago

Mantis Chess Engine

A tournament-ready chess engine written in Odin with NNUE evaluation and world-class search optimizations.

Estimated Strength: 2400-2650 Elo

Features

Evaluation

  • ✅ NNUE (Efficiently Updatable Neural Network)
  • ✅ HalfKAv2 architecture
  • ✅ Incremental updates
  • ✅ Compatible with standard NNUE files

Search

  • ✅ Negamax with Alpha-Beta Pruning
  • ✅ Principal Variation Search (PVS)
  • ✅ Iterative Deepening
  • ✅ Quiescence Search
  • ✅ Aspiration Windows
  • ✅ Check Extensions

Pruning & Reductions

  • ✅ Transposition Table (configurable 1-1024 MB)
  • ✅ Late Move Reductions (Logarithmic formula)
  • ✅ Null Move Pruning (R=2)

Move Ordering

  1. Hash Move (from TT)
  2. MVV-LVA Captures
  3. Killer Heuristic (2 per ply)
  4. History Heuristic (piece-to-square)
  5. Other moves

Time Management

  • ✅ Smart time allocation
  • ✅ Handles all UCI time controls
  • ✅ Periodic time checks
  • ✅ Iterative deepening control

UCI Protocol

  • ✅ Full UCI support
  • ✅ Configurable Hash size
  • ✅ Custom NNUE network loading

Build

Quick Build (Optimized for Speed)

./build_optimized.sh

Manual Build

For maximum performance (recommended):

odin build . -out:mantis -o:speed -microarch:native

For portability (works on any x86-64 CPU):

odin build . -out:mantis -o:speed

Debug build (not recommended for play):

odin build . -out:mantis

⚠️ Important: Always use -o:speed for competitive play! Debug builds are 10-30x slower.

Usage

Interactive Mode

./mantis

UCI Commands

uci
setoption name Hash value 128
setoption name EvalFile value nn-c0ae49f08b40.nnue
position startpos
go depth 10
quit

With Time Control

position startpos moves e2e4 e7e5
go wtime 60000 btime 60000 winc 1000 binc 1000

UCI Options

Option Type Default Range Description
Hash spin 64 1-1024 Transposition table size (MB)
EvalFile string nn-c0ae49f08b40.nnue - NNUE network file path
OwnBook check true - Enable internal opening book
BookFile string 2moves_v1.epd - Opening book EPD file
Move Overhead spin 10 0-5000 Network latency compensation (ms)
MultiPV spin 1 1-500 Number of principal variations
Ponder check false - Enable pondering (background thinking)
SyzygyPath string empty - Syzygy tablebase directory
SyzygyProbeLimit spin 7 0-7 Maximum tablebase pieces to probe
Threads spin 1 1-512 Number of search threads
Contempt spin 12 -100-100 Root eval bias against draws
SearchStats check false - Print detailed search counters
RootDebugTrace check false - Print root search diagnostics
StagedMovePicker check false - Enable staged move picker experiment

UCI Tuning Options

These options expose bounded search constants for SPSA, cutechess, and local self-play tuning without recompiling:

Option Default Range
AspirationWindow 35 5-200
NmpMinDepth 3 2-6
NmpReductionBase 2 0-4
NmpReductionDiv 6 3-10
RfpMargin 25 10-150
RfpDepth 8 5-10
ProbcutDepth 5 3-8
ProbcutMargin 40 0-300
ProbcutReduce 4 1-6
IirMinDepth 4 3-8
SeDepth 8 5-12
SeMargin 2 0-8
SeReducedDiv 2 1-4
LmrMinDepth 3 2-5
LmrImprovingAdj -1 -4 to 4
LmrHistoryGoodAdj -1 -4 to 4
LmrHistoryBadAdj 1 -4 to 4
LmrHistoryGoodThresh 2000 0-10000
LmrHistoryBadThresh -2000 -10000 to 0
FutilityMargin 65 30-400
FutilityMaxDepth 3 1-6
LmpBase 2 1-4
LmpDiv 2 1-4
LmpMaxDepth 8 3-12
RazorMargin 80 0-300
RazorMaxDepth 3 1-5
DeltaPruningMargin 250 0-1200
SeePruneThreshold -50 -300 to 0
ContinuationScoreDiv 12 1-64

For dependency-free paired SPSA tuning, build a current engine binary and run:

python3 nevergrad_tuner.py --engine ./mantis --optimizer spsa \
  --budget 80 --games 20 --movetime 200 --concurrency 4

Testing

Fixed Depth Search

position startpos
go depth 10

Time-Controlled Search

position startpos
go wtime 60000 btime 60000

Perft (Move Generation Verification)

perft 5

Compatible GUIs

  • Cute Chess CLI - Automated testing
  • Arena Chess - GUI play
  • Any UCI-compatible interface

Performance

  • Node Reduction: 80-90% vs naive alpha-beta
  • NPS: 900k+ nodes per second (unoptimized build)
  • Effective Depth: 2-3 ply deeper per second vs basic search

Architecture

Mantis/
├── board/          # Board representation, move making
├── constants/      # Chess constants
├── eval/           # Evaluation (PST, piece values)
├── moves/          # Move generation
├── nnue/           # NNUE evaluation
├── search/         # Search algorithms
│   ├── search.odin      # Negamax, PVS, extensions
│   ├── sort.odin        # Move ordering
│   ├── tt.odin          # Transposition table
│   └── time_manager.odin # Time management
├── uci/            # UCI protocol
├── utils/          # Utility functions
└── zobrist/        # Zobrist hashing

Development Roadmap

Completed ✅

  • NNUE Evaluation
  • Full search optimizations (TT, LMR, NMP)
  • Advanced move ordering (Hash, MVV-LVA, Killers, History)
  • Time management
  • UCI protocol

Future Enhancements

  • Singular Extensions (+40-60 Elo)
  • Multi-PV support
  • Lazy SMP (parallel search, +150-200 Elo)
  • Syzygy Tablebases
  • Large-scale automated tuning runs

Documentation

  • DEVELOPMENT_SUMMARY.md - Complete development history
  • NEXT_STEPS.md - Future optimization roadmap
  • FINAL_SUMMARY.md - Comprehensive feature summary

Author

Built with Odin