ben-manes / caffeine / #5626

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Keep the simulator SimpleClimber faithful to BLC's climber

SimpleClimber is a readable reference for the production hill climber,
so it should represent the algorithm at full quality -- simpler only by
shedding library machinery, not by being a weaker climber. Two
algorithmic improvements BLC has were missing:

- Direction: it started every cache shrinking the window. BLC grows the
  window first for small caches (setStepSize's positive sign at
  maximum <= SMALL_CACHE_THRESHOLD, from "Improve hill climber
  adaptation at small cache sizes"). Start increaseWindow = isSmallCache.

- Freeze: the large-cache path set sampleSize = Integer.MAX_VALUE once
  the step decayed below 0.01, which made adapt()'s restart unreachable
  -- a permanent stall through any later workload shift. BLC never
  freezes; it keeps decaying the step and revives it on a hit-rate
  change. Drop the freeze and floor sampleSize at 1 so the restart
  stays reachable.

The default sample-decay-rate is 1.0, so the period was already fixed
like BLC's; only the freeze and initial direction diverged. Verified on
the corda_large + 5x loop + corda_large stress trace and a spread of
bundled LIRS traces at 512: net positive (corda +2.05, sprite +1.32,
multi3 +1.17; small losses within noise), tracking product.Caffeine.
Pinned by SimpleClimberTest.

4139 of 4150 branches covered (99.73%)

8411 of 8412 relevant lines covered (99.99%)

1.0 hits per line