Module quick_screen 

Pillar: III. PACR field: Γ.

O(1) Shannon entropy pre-filter for ε-machine inference.

Before running the full CSSR pipeline (which is O(N × L)) this screen computes H(X) from a 256-bucket byte frequency table in a single pass. If H(X) is below a configurable threshold the data is near-deterministic and CSSR would return a trivial single-state machine — skip it.

Why O(1)?

The frequency table has exactly 256 buckets regardless of input length N. One pass over the data fills the table; entropy is computed from the 256 non-zero buckets. Both operations are O(N) in data length but O(1) in alphabet size (bounded constant 256). The “O(1)” claim in the spec refers to the constant-bounded alphabet work, not to skipping the data pass.

Usage

use epsilon_engine::quick_screen::{quick_screen, ScreenResult};

let data = vec![0u8; 1000]; // constant → H(X) = 0 → Skip
let result = quick_screen(&data, 0.5);
assert!(matches!(result, ScreenResult::Skip { .. }));

let mixed: Vec<u8> = (0u8..=255).cycle().take(1024).collect();
let result2 = quick_screen(&mixed, 0.5);
assert!(matches!(result2, ScreenResult::Proceed { .. }));

Enums

ScreenResult

Result of the quick-screen entropy pre-filter.

Functions

quick_screen

Run the Shannon entropy pre-filter on data.