12. Environment variables and configuration

The library exposes a number of environment variables to tune performance, tie‑breaking, and debugging without changing code.

12.1 Depth and scheduling

Variable	Default	Description
`RM_DEPTH_MODE`	`est`	Controls depth method used in `decoders._depth_from_solution`. • `"est"`: use fast estimator `rmcore.tdepth_from_punctured`. • `"sched"`: try exact T-depth scheduler.
`RM_SCHED_BUDGET`	`20000`	Search budget (nodes) for the T-depth scheduler when `RM_DEPTH_MODE="sched"`. Higher values yield better colorings but take longer.
`RM_TDEPTH_COLOR_NODES`	`500000`	Max nodes explored by DSATUR in `tdepth.cpp`. If limit hit, falls back to greedy.
`RM_TDEPTH_COLOR_MS`	`50`	Max wall-clock time (ms) for DSATUR.

Variable	Default	Description
`RM_PARALLEL`	`ON`	If unset, parallelism (TBB/OpenMP) is enabled where available. Set to `"0"`, `"false"`, or `"no"` to force sequential execution.
`RM_DETERMINISTIC`	`OFF`	If set to a truthy string, list decoders break ties using a deterministic hash key (distance + hash) instead of `std::nth_element`.

Variable	Default	Description
`RM_AUTOTUNE_CACHE`	`~/.rmsynth_autotune.json`	Path to the JSON cache file.
`RM_AUTOTUNE_SELECTOR`	`quality-under-target`	Strategy for `calibrate_single`. Options: `"quality-under-target"`, `"pareto"`.
`RM_AUTOTUNE_PARETO_DIST`	`1`	Pareto distance slack.
`RM_AUTOTUNE_PARETO_LAT`	`1.10`	Pareto latency factor.
`RM_AUTOTUNE_TRIALS`	`4`	Number of synthetic words sampled per configuration.
`RM_AUTOTUNE_SEED`	`123`	RNG seed for autotuning.

Variable	Default	Description
`RM_CHECKS`	`OFF`	If set to a truthy value, enables contract checking in `Optimizer`, asserting invariants on every run.

Variable	Default	Description
`RM_SNAP_BB_MS`	`15`	Max time (ms) for branch‑and‑bound "strong SNAP".
`RM_SNAP_BB_NODES`	`100000`	Max nodes for branch‑and‑bound SNAP.
`RM_SNAP_BB_POOL`	`snap_pool`	Pool size for branch-and-bound SNAP (defaults to the `snap_pool` argument).
`RM_RPA2_MAX_PERMS`	`unset`	Limits permutations in RPA-2 strategies. If unset, uses a modest default set.
`RM_OSD2_MAX_PAIRS`	`unset`	Caps number of pairs checked in OSD-2.
`RM_OSD3_MAX_TRIPLES`	`unset`	Caps number of triples checked in OSD-3.