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, (6) OSSHNL-109 error after SKILL edit,
(7) library not found / ddGetObj returns nil / Virtuoso started from wrong directory.
Covers: the resultsDir binding trap (MOST COMMON), OSSHNL-109 extraction timestamp
stale error, stale netlists, sim setup disrupting sessions, direct spectre
invocation as bypass, library-not-registered diagnosis, and PSF signal naming.
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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, (6) OSSHNL-109 error after SKILL edit,
(7) library not found / ddGetObj returns nil / Virtuoso started from wrong directory.
Covers: the resultsDir binding trap (MOST COMMON), OSSHNL-109 extraction timestamp
stale error, stale netlists, sim setup disrupting sessions, direct spectre
invocation as bypass, library-not-registered diagnosis, and PSF signal naming.
author
Claude Code
version
2.3.0
date
"2026-04-20T00:00:00.000Z"
argument-hint
["symptom","e.g. \"run() returns nil\" or \"OSSHNL-109\""]
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:
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 2b: design() Not Called — evalstring() First-Expression Bug
Symptom: vcli sim netlist fails even on a registered library. si.foregnd.log has NO new
entry (last entry is days old). design() from bridge returns nil.
Root cause: evalstring() in SKILL evaluates only the FIRST top-level expression in the string.
The old setup_skill sent three newline-separated expressions:
One top-level expression → evalstring evaluates all three.
Diagnosis: Run vcli skill exec 'design()' — if output is nil, design context is missing.
Manually run vcli skill exec 'design("LIB" "CELL" "schematic")' to set it.
Root Cause 3: OSSHNL-109 — Extraction Timestamp Stale
Root cause: dbSave(cv) writes the OA file but does NOT update the extraction
timestamp. schCheck(cv) is what updates it. Calling dbSave without schCheck
leaves the timestamp stale; the next incremental createNetlist sees a mismatch.
Fix: Run schCheck(cv) before dbSave(cv). Or use vcli sim netlist — it
auto-recovers by running schCheck + dbSave and retrying when createNetlist returns nil.
; Get the cv (3-arg form opens "a" mode in IC23; fallback for Ocean-held cv)
cv = dbOpenCellViewByType("lib" "cell" "view")
unless(cv
cv = car(setof(ocv dbGetOpenCellViews()
and(ocv~>libName=="lib" ocv~>cellName=="cell" ocv~>mode=="a"))))
chk = schCheck(cv)
when(car(chk)==0 dbSave(cv)) ; only save if no check errors
Also note: dbReplaceProp(inst "w" ...) sets the display parameter, NOT the
netlisted simW. For SMIC PDK n12/p12 width changes, use:
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.
Root Cause 5: Library Not Registered in Virtuoso Session
Symptom: vcli sim netlist returns an error like:
Library 'FT0001A_SH' is not registered in the current Virtuoso session.
Virtuoso was started from '/home/meow/git/virtuoso-cli'.
Or ddGetObj("FT0001A_SH") returns nil from the bridge.
Root cause: Virtuoso was started from a directory that has no cds.lib including
the target library. The DD database is populated at startup from cds.lib files found
via CDSHOME, site, and user paths — but NOT automatically from arbitrary directories.
Diagnosis: Check Virtuoso's working directory in CDS.log:
# Regenerate netlist — auto-recovers from OSSHNL-109 via schCheck+dbSave retry
vcli sim netlist --lib <lib> --cell <cell>
vcli sim netlist --lib <lib> --cell <cell> --recreate # force full recreation
Solution B: 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)
⚠️ Run from the schematic/ directory, NOT from netlist/ — relative paths inside
the netlist resolve from schematic/. Running from netlist/ causes CMI-2011 (cannot open input file).
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)
Open testbench in Virtuoso → Launch ADE L
Simulation → Netlist and Run (or Netlist → Create)
Confirm input.scs is updated, then virtuoso sim run works again
PSF Signal Naming
Instances inside a subcircuit instantiated as I0 in the testbench:
