Mutation sigma annealing #123

New Issue

2026-08-29T19:04:19+02:00

SirStone commented

2026-08-29 19:04:19 +02:00

What to build

Replace the constant mutation sigma with a decay schedule so that mutations are large early (exploration) and small late (exploitation).

Currently Sigma = 0.03 is constant for all generations. Over 100 generations, accumulated mutation variance approaches the initialization range, destabilizing late-game optimization.

Acceptance criteria

mutate uses sigma = initialSigma * exp(-generation / annealingHalfLife)
Default annealingHalfLife = 50 generations
Constant Sigma = 0.03 preserved as fallback for experimentation
Formula tested against known convergence behavior (e.g., sigma approaches ~0.004 at generation 100)
Existing when isMainModule self-check in ga.nim still passes

Blocked by

None - can start immediately

Parent

Closes part of #118

## What to build Replace the constant mutation sigma with a decay schedule so that mutations are large early (exploration) and small late (exploitation). Currently Sigma = 0.03 is constant for all generations. Over 100 generations, accumulated mutation variance approaches the initialization range, destabilizing late-game optimization. ## Acceptance criteria - mutate uses sigma = initialSigma * exp(-generation / annealingHalfLife) - Default annealingHalfLife = 50 generations - Constant Sigma = 0.03 preserved as fallback for experimentation - Formula tested against known convergence behavior (e.g., sigma approaches ~0.004 at generation 100) - Existing when isMainModule self-check in ga.nim still passes ## Blocked by None - can start immediately ## Parent Closes part of #118

SirStone added the ready-for-agent label 2026-08-29 19:05:49 +02:00

SirStone closed this issue

2026-08-29 20:17:46 +02:00

SirStone commented

2026-08-29 20:17:46 +02:00

Implemented in commit a730a9e

Summary: Replaced constant mutation sigma with decay schedule: sigma = initialSigma * exp(-generation / annealingHalfLife). Default annealingHalfLife=50 generations provides exploration early (large mutations) and exploitation late (small mutations).

Files:

vapourbot_garage/src/vapourbot/ga.nim - mutate() function sigma decay formula

Implemented in commit a730a9e **Summary:** Replaced constant mutation sigma with decay schedule: sigma = initialSigma * exp(-generation / annealingHalfLife). Default annealingHalfLife=50 generations provides exploration early (large mutations) and exploitation late (small mutations). **Files:** - `vapourbot_garage/src/vapourbot/ga.nim` - mutate() function sigma decay formula

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Reference: SirStone/SirRoboGarage#123