Ohm¶

The self-evolving engine. See the full blog post: ../../blog/the-ohm-runtime.md

Definition¶

Ohm (Ω) is the Senter variant that carries its own evolution engine inside the model file. It's a single artifact — model weights + genome + validation set + evolution engine — that runs continual Darwin-style evolutionary merging while it serves.

The name is double-loaded: - Ω (omega) — the symbol, the unit, the constant. The standing wave. - ohm / ॐ — the universal vibration, the always-on.

What it is¶

A regular model file is just weights. An Ohm model file is a self-contained bundle:

{
  "format_version": "ohm/1.0",
  "model_type": "Senter-Ohm-32A8B",
  "active_weights_path": "./active.safetensors",
  "ohm_state": { /* genome + sigma + best_loss + counters */ },
  "parent_b": { /* the other parent for the merge */ },
  "validation_set": { "path": "...", "n_examples": 500 },
  "evolution_config": {
    "sigma_init": 0.05, "sigma_min": 0.01,
    "accept_threshold": 0.0,   // strict improvement only
    "cycle_interval_sec": 300, // every 5 minutes
    "enabled": true
  }
}

The Ohm loop¶

Runs as a background thread while the model is serving:

while model is loaded:
    if time since last cycle > cycle_interval:
        new_genome = mutate(current_genome, sigma)
        candidate_weights = paper_exact_merge(active, parent_b, new_genome)
        candidate_loss = evaluate(candidate_weights, validation_set)
        if candidate_loss < best_loss:
            atomic_swap(active_weights, candidate_weights)
            best_loss = candidate_loss
        else:
            sigma = max(sigma_min, sigma * sigma_decay)
        write_state(ohm_state)

Key safety property: the model never serves worse outputs than its best-so-far. Evolution is one-directional.

Why it works¶

Three properties: 1. Fast merge — the Darwin paper-exact merge is seconds, not hours 2. Cheap evaluation — 500-example held-out set is ~30s on a 3090 3. Bounded evolution — strict improvement acceptance

Combined: full evolution cycle in under 5 minutes while the model serves. 12 cycles/hour, ~300 cycles/day. Small improvements compound.

The `.ohm` file format¶

File extension: .ohm (e.g., senter-ohm-32a8b.ohm)
Runtime: ohmd (the daemon that loads .ohm files and runs evolution)
CLI flag for llama-server: --ohm
State file: ohm_state.json (inside the bundle)
Log format: /ohm/log.jsonl (one line per candidate)