---
title: Phase benchmark
family: baselines-diagnostics
summary: Plays complete games with the shared hand-written policy and reports score, clears, reveals, board height, search work, and early stops.
status: support-only
evidence: repository-verified
reads: public
---

A stopwatch and a set of scales for the policy that most of the native
experiments are built on top of: play some complete games, and report six
numbers about *how* they went rather than one number about how they ended.

<EvidenceLabel status="support-only" evidence="repository-verified" reads="public" />

## The intuition

Two policies can average the same score for completely different reasons. One
survives a long time while clearing steadily; another lives a shorter life and
gets rescued by one enormous chain. On a heavy-tailed score those look the
same in a mean, and they behave completely differently when you change anything
about them.

So this harness reports the score, and then the mechanism underneath it:

- **mean moves**: how long the games lasted, which for this game is nearly the
  same statement as the score;
- **clears per move** and **reveals per move**: the flow rates the board has
  to sustain against the rise (see the
  [family page](/approaches/baselines-diagnostics) for why 2.4 and 1.4 are the
  numbers that matter);
- **mean maximum height**: how close to the ceiling the policy was living;
- **work per move** — search cost in the repository's own unit, so a strength
  change can be separated from a budget change;
- **censored games**: how many were still alive at the move cap, whose score
  is therefore only a lower bound.

Every one of those is public information about the trajectory. Nothing here
looks under a gray disc or forward in the tape.

## How it works

1. Start a headless game from a seed.
2. Ask the shared native behaviour policy for a column. The default
   configuration is a three-ply search with five imagined chance outcomes per
   node, a one-million-unit work cap per move, and a large negative value for
   dying.
3. Play the move, add its cleared and revealed discs to the running totals,
   record the board's maximum height, and add the search work the move cost.
4. Stop at game over or at the move cap (default 1,000), and mark the game
   censored if the cap ended it.
5. After all games, print one JSON line: games, mean score, mean moves, clears
   per move, reveals per move, mean maximum height, work per move, wall seconds,
   censored count. With `--trace` it also prints one line per move with the
   disc, the column, the height, occupancy, cover count, potential and the
   board.

## What happened

**No retained result.** The [experiment index](/docs/research/experiment-index)
records this source as support-only and repository-verified. It says that "no
durable standalone result was located";
[audit 04](/docs/exploratory/audit-04-blind-spots) §B.2 lists it among the
sources whose question has no lane. This page describes the instrument from its
code and quotes no scores for it.

<TechnicalDetails title="The technical record">

**Status: support-only; repository-verified.** No ledger entry and no task
record was located, so no measurement is attributed to this source.

Defaults: 8 games from seed `0x3d700100`, `--max-moves 1000`, `--depth 3`,
`--samples 5`, `--max-work 1000000`, `--terminal-utility -1000000`. The policy
is `drop7::cfpi::chooseBehaviorAction` in `src/core/native/public-behavior.hpp`
— the same shared phase behaviour that several other experiments freeze and
build on, including the
[tail-survival CEM](/approaches/constructive-reservoir/tail-survival-cem), which
records its version as a 165-weight public evaluator inside a depth-3,
internal-width-two, three-stratum selective search.

Build it like any standalone experiment:
`make experiment SOURCE=approaches/baselines-diagnostics/phase-benchmark/phase-benchmark.cpp`
(see the [reproducibility guide](/docs/reproducibility); use `CXX=clang++`).

Two cautions when reading its output. The clears- and reveals-per-move figures
are computed as the mean per-game total divided by the mean moves, not as the
mean of the per-game rates, so they are not paired per-game statistics. And the
default 8 games is a smoke test, not a cohort — [benchmarks](/docs/benchmarks)
defines the tiers that count.

Source: `phase-benchmark.cpp`.

</TechnicalDetails>

## What this taught us, and what is still open

- The vocabulary this project judges policies in — flow, height, work,
  censoring — is implemented here, and it is deliberately richer than "mean
  score".
- What that vocabulary said about the shared phase policy is not recorded
  anywhere in this repository. The instrument survived; its readings did not.
- Any future use should state its seed range and role up front, because this
  program has no seed-lease bookkeeping of its own and will happily replay any
  range it is given.