Constant ENV_RESTART_MODE 

pub const ENV_RESTART_MODE: &str = "ATUNE_RESTART_MODE";

The environment variable naming a restart child’s restart mode: fresh or shrink_perturb.

Set only for the first run of a restart child, beside ENV_RESTART_SEED. A fresh child has no ENV_CHECKPOINT and re-initializes from scratch; a shrink_perturb child loads ENV_CHECKPOINT, then shrinks the weights by ENV_RESTART_SHRINK and adds noise of scale ENV_RESTART_NOISE. Absent for every other trial, plain forks and resumes included.