ocean-netlist-regen

name	ocean-netlist-regen
description	Fix Ocean SKILL simulation failures after schematic edits. Use when: (1) run() returns nil in <1s with no spectre.out, (2) createNetlist() returns nil, (3) sim results are all nil after changing W/L to design variables, (4) netlist file was deleted or is stale, (5) sim run previously worked but now fails after calling `sim setup` again. Covers: the resultsDir binding trap (MOST COMMON), stale netlists, sim setup disrupting sessions, direct spectre invocation as bypass, and PSF signal naming (I0.NM0 prefix).
author	Codex
version	2.0.0
date	"2026-04-06T00:00:00.000Z"

Ocean run() Reliability & Netlist Regeneration

Problem

Ocean's run() silently returns nil. All measurement results are nil. Spectre never runs. No error is reported.

Context / Trigger Conditions

• run() completes quickly and returns nil instead of the resultsDir path
• No spectre.out or stale one in psf directory
• createNetlist(?recreateAll t) returns nil
• Previously called sim setup or changed resultsDir to a different path
• Previously working simulation stops producing results

---

Root Cause 1: resultsDir Change Breaks run() ⚠️ MOST COMMON

The ADE session binds run() to the resultsDir that was active when the session was first established from the GUI. Changing it to ANY other path causes run() to silently return nil.

; ✅ Works — same path as ADE session
resultsDir("/tmp/opt_5t_ota")
run()   ; → "/tmp/opt_5t_ota"

; ❌ Breaks run() — different path
resultsDir("/tmp/new_dir")
run()   ; → nil (silent failure!)

; ✅ Restore original path, run() works again
resultsDir("/tmp/opt_5t_ota")
run()   ; → "/tmp/opt_5t_ota"

Find the canonical resultsDir from the runSimulation script:

cat <netlist_dir>/runSimulation | grep "\-raw"
# → -raw ../../../../../../../../tmp/opt_5t_ota/psf
# Canonical path = /tmp/opt_5t_ota

Fix in virtuoso-cli: sim run no longer auto-sets resultsDir to a temp dir (that was overriding the ADE session path). If resultsDir is nil, sim run now returns a clear error message.

---

Root Cause 2: sim setup Disrupts Active Session

Calling virtuoso sim setup sends design("lib" "cell" "view") which can reset the Ocean session state. After this, run() returns nil.

Symptom: run() worked → called sim setup → run() now returns nil.

Fix: Don't call sim setup again if a working session exists. Check:

virtuoso skill exec 'asiGetSession(hiGetCurrentWindow())'
# → stdobj@0x... means session is alive

---

Root Cause 3: Stale or Missing Netlist

After editing a schematic (e.g., adding desVar variables), the netlist becomes stale. createNetlist() requires an ADE L window open for that cell — without it, returns nil.

---

Solution A: Restore resultsDir (for Root Cause 1)

virtuoso skill exec 'resultsDir("/tmp/opt_5t_ota")'
virtuoso sim run --analysis dc --timeout 60

---

Solution B: Direct Spectre Invocation (most reliable, bypasses Ocean)

NETLIST_DIR="/path/to/simulation/cell/spectre/schematic/netlist"
PSF_DIR="/tmp/my_results/psf"
mkdir -p "$PSF_DIR"

cd "$NETLIST_DIR" && spectre input.scs \
  +escchars \
  +log "$PSF_DIR/spectre.out" \
  -format psfxl -raw "$PSF_DIR" \
  +mt -maxw 5 -maxn 5

Then read results:

virtuoso skill exec 'openResults("/tmp/my_results/psf")'
virtuoso sim measure --analysis dcOp \
  --expr 'getData("I0.NM0:gm" ?result "dcOpInfo")'

Advantages: ~200–300ms, no ADE session dependency, works even when Ocean is broken.

---

Solution C: Add Analyses to Netlist Directly

The ADE-generated input.scs may only have DC. Add AC without opening ADE:

sed -i 's/^dcOpInfo info what=oppoint where=rawfile$/dcOpInfo info what=oppoint where=rawfile\nacSweep ac start=1 stop=10G dec=20 annotate=status/' input.scs

---

Solution D: Regenerate via ADE GUI (for missing netlist)

1. Open testbench in Virtuoso → Launch ADE L
2. Simulation → Netlist and Run (or Netlist → Create)
3. Confirm input.scs is updated, then virtuoso sim run works again

---

PSF Signal Naming

Instances inside a subcircuit instantiated as I0 in the testbench:

Context	Correct	Wrong
Device oppoint	getData("I0.NM0:gm" ?result "dcOpInfo")	getData("/NM0:gm")
Node voltage (AC)	VF("net1") or VF("VOUT")	VF("/VOUT")
DC node voltage	VDC("net1")	—

Find actual signal names:

strings /tmp/results/psf/acSweep.ac | grep "^I0\."

Or in SKILL: openResults("/psf/path") selectResult('acSweep) VF("net1") — if it returns srrWave:0x..., the signal name is correct.

---

Diagnostic Checklist

1. cat runSimulation | grep -raw → what is the canonical resultsDir?
2. resultsDir() → does it match the canonical path?
3. run() → returns path (OK) or nil (broken)?
4. PSF dir has .dc/.ac files → simulation produced data
5. PSF dir only has simRunData, artistLogFile, variables_file → simulation failed

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Key Files

<project>/simulation/<cell>/spectre/schematic/netlist/
├── input.scs       # Top-level: parameters, model includes, analyses
├── netlist          # Subcircuit from schematic
├── runSimulation    # Actual spectre command ADE uses (shows original PSF path)
└── netlistFooter    # Testbench instances and stimuli

Notes

• design("lib" "cell" "view") returns nil when no ADE window is open for that cell
• sim setup should only be called once per ADE session
• system("find / ...") hangs the SKILL daemon — blocked by virtuoso-cli bridge
• After bridge hang, restart: Ctrl+C in CIW, reload bridge.il + RBStart

See also: SKILL bridge scoping rules in ~/.Codex/projects/.../memory/feedback_skill_bridge_scoping.md