rat-ultraloop-ppa

Drive the DC-based PPA optimization loop to convergence. Wraps `rtl-ppa-optimize-dc` in an auto-repeat loop with three termination tiers: early plateau, normal convergence, max cycles. On normal convergence, runs full Phase 5 regression and writes `rtl-verify-done` + `ppa-opt-done`.

<Use_When>

• User says "ultraloop PPA", "PPA auto-loop", "optimize PPA until converge"
• Verified RTL ready for PPA refinement
• Industrial flow with dc_shell/genus available </Use_When>

<Do_Not_Use_When>

• Preconditions of rtl-ppa-optimize-dc are not met
• User wants a single iteration only (use rtl-ppa-optimize-dc)
• Design is still under architectural change (freeze first) </Do_Not_Use_When>

Invocation

/rtl-agent-team:rat-ultraloop-ppa [top_module]

Loop Body

import json, time, shutil, subprocess, pathlib

TOP = ARGUMENTS or json.load(open("requirements.json"))["top_module"]

# Hard preconditions
assert shutil.which("dc_shell") or shutil.which("genus"), \
    "rat-ultraloop-ppa requires dc_shell or genus in PATH"

req = json.load(open("requirements.json"))
assert "ppa_targets" in req, \
    "requirements.json missing ppa_targets — run rtl-ppa-optimize-dc once to scaffold"

max_cycles = int(req["ppa_targets"].get("convergence", {}).get("max_cycles", 4))

# Initialize state
state_path = pathlib.Path(".rat/state/ppa-loop-state.json")
if not state_path.exists():
    state = {
        "mode": "ppa-loop",
        "cycle": 0,
        "max_cycles": max_cycles,
        "weights": req["ppa_targets"].get("weights", {"timing":0.7, "power":0.2, "area":0.1}),
        "convergence": {
            "delta_pct": req["ppa_targets"].get("convergence", {}).get("delta_pct", 2.0),
            "streak_required": req["ppa_targets"].get("convergence", {}).get("streak", 3),
            "early_plateau_pct": req["ppa_targets"].get("convergence", {}).get("early_plateau_pct", 1.0),
            "history": [],
        },
        "allowed_edit_scope": [f"rtl/{TOP}/**/*.sv"],
        "frozen_scope": ["rtl/common/**", "rtl/pkg/**", "rtl/intf/**"],
        "last_cycle_timestamp": int(time.time()),
        "auto_continue_minutes": 30,
    }
    state_path.parent.mkdir(parents=True, exist_ok=True)
    state_path.write_text(json.dumps(state, indent=2))

# The LLM executes the following iterative protocol. The block below is
# CONCEPTUAL pseudo-code (Skill() is not a callable Python function) —
# the real mechanism is a slash-command invocation followed by reading
# the verdict file that the orchestrator writes.

Loop Protocol (the LLM executes these steps iteratively)

For each cycle in 1..max_cycles:

1. Invoke action skill — call /rtl-agent-team:rtl-ppa-optimize-dc <TOP>. This runs exactly one PPA iteration via the orchestrator, which writes docs/ppa-opt/iter-{cycle}/verdict.txt on completion.

1a. Refresh auto-continue timestamp — update last_cycle_timestamp in .rat/state/ppa-loop-state.json to the current epoch seconds BEFORE invoking rtl-ppa-optimize-dc. This ensures the 30-minute stop-gate.sh window restarts each cycle, not only at loop start. ```python import json, time, pathlib, os, tempfile, fcntl

STATE_PATH = pathlib.Path(".rat/state/ppa-loop-state.json")
LOCK_PATH = str(STATE_PATH) + ".lock"

with open(LOCK_PATH, "a") as lock_f:                 # long-lived lock file; never replaced
    fcntl.flock(lock_f.fileno(), fcntl.LOCK_EX)
    try:
        s = json.loads(STATE_PATH.read_text())
        s["last_cycle_timestamp"] = int(time.time())
        dir_ = STATE_PATH.parent
        fd, tmp = tempfile.mkstemp(prefix=".ppa-state-", dir=str(dir_))
        try:
            with os.fdopen(fd, "w") as tmp_f:
                json.dump(s, tmp_f, indent=2)
            os.replace(tmp, str(STATE_PATH))         # atomic swap
        except BaseException:
            try:
                os.unlink(tmp)
            except OSError:
                pass
            raise
    finally:
        fcntl.flock(lock_f.fileno(), fcntl.LOCK_UN)
```
Uses the same atomic lock-file + `os.replace()` pattern as `compute_delta.py`:
a `.lock` file is held via `fcntl.flock` during the read-modify-write cycle,
and the updated state is written to a temp file then atomically renamed
onto the canonical path. This prevents `stop-gate.sh` from observing a
truncated state file between steps.

2. Read verdict — read docs/ppa-opt/iter-{cycle}/verdict.txt. Expected values: CONTINUE, CONVERGED_STREAK, CONVERGED_TARGETS, EARLY_PLATEAU, MAX_CYCLES, TIMING_REGRESSION.

3. Dispatch by verdict:

   • CONVERGED_STREAK or CONVERGED_TARGETS:

     • Invoke /rtl-agent-team:rtl-p5-verify --mode=final --source=ppa-opt for full regression confirmation.
     • Write .rat/state/rtl-verify-done with ppa-opt-converge cycle {cycle}\n.
     • Write .rat/state/ppa-opt-done with converge cycle {cycle}\n (triggers P6 cascade re-review if the design-note was written prior).
     • Generate docs/ppa-opt/final-report.md (see template below).
     • Remove .rat/state/ppa-loop-state.json.
     • Exit the loop.

   • EARLY_PLATEAU:

     • Generate reviews/ppa-opt/early-plateau-escalation.md.
     • Remove .rat/state/ppa-loop-state.json.
     • Exit the loop.

   • MAX_CYCLES:

     • Generate docs/ppa-opt/final-report.md with exit_reason MAX_CYCLES (best-so-far iteration recorded).
     • Remove .rat/state/ppa-loop-state.json.
     • Exit the loop.

   • TIMING_REGRESSION:

     • Orchestrator already rolled back the patch via git checkout -- rtl/<top>.
     • Generate reviews/ppa-opt/timing-regression-escalation.md.
     • Remove .rat/state/ppa-loop-state.json.
     • Exit the loop.

   • CONTINUE:

     • Proceed to the next cycle (increment cycle counter, re-enter step 1).

4. Safety net — if the loop falls through max_cycles without a terminal verdict (should not happen), generate final-report with exit_reason LOOP_EXIT_UNEXPECTED and remove the state file.

Note: The per-cycle refresh of last_cycle_timestamp (step 1a) is critical: stop-gate.sh uses it to decide whether the 30-min auto-continue window is still active. Without it, long DC iterations would be interrupted 30 minutes after loop start even when the loop is making progress.

Final Report (docs/ppa-opt/final-report.md)

# PPA Optimization Final Report

- Target module: {TOP}
- Cycles executed: {N} / {max_cycles}
- Exit reason: CONVERGED | EARLY_PLATEAU | MAX_CYCLES

## Iteration history

| iter | wns_ns | power_mw | area_um2 | weighted_Δ |

## Best-so-far iteration
- iter: {best_iter}
- wns_ns: {}  power_mw: {}  area_um2: {}

## Next steps
- If CONVERGED: full Phase 5 regression passed → proceed to Phase 6 design note
- If EARLY_PLATEAU: see reviews/ppa-opt/early-plateau-escalation.md
- If MAX_CYCLES: consider raising max_cycles in requirements.json["ppa_targets"]["convergence"]

30-Min Auto-Continue

Reuses the stop-gate.sh escalation pattern: when .rat/state/ppa-loop-state.json is present with mode == "ppa-loop" and last_cycle_timestamp + auto_continue_minutes*60 > now, the hook auto-continues instead of stopping.