paramrange_examples

paramrange_examples — CMC default-range idiom + sweep fixes (Enhancement-56)

Demonstrates Enhancement-56: the fixes found by running the whole VA_TEST corpus (92 standalone industry models) end-to-end through ngspice (op/AC/tran/noise) instead of compile-only, using the committed openvaf-r and ngspice-46.

What was broken

• Parameter DEFAULTS were range-checked at setup. CMC-standard models declare a default outside the parameter's own range as the "feature disabled" state — diode_cmc's CORECOVERY = 0.0 from (0.0:1.0], FBH-HBT's Fb = 0.0 from (0.0:inf), and friends — and expect range constraints to bind only user-given values. OpenVAF validated the default too, so the stock CMC models (diode_cmc, bsimcmg-110, fbh_hbt, psphv fragments, …) were rejected at setup with "Parameter … is out of bounds". Defaults are now exempt; given values are still validated (both from ranges and exclude constraints).
• A $fatal/$finish raised during setup surfaced as ngspice's baffling "impossible error - can't occur". Models validate their configuration at setup (HiSIM's $port_connected/COSUBNODE guards) and reject it by design; ngspice now says "a Verilog-A device rejected its configuration during setup ($finish raised)" — right next to the model's own message.
• A singular AC matrix during noise analysis crashed ngspice with a SIGABRT — noisean.c ignored NIacIter's return, and the noise adjoint solve then asserted on the unfactored matrix. It now aborts the noise analysis cleanly ("AC solution failed at … Hz"); the noise analysis also honors E-55's deferred $finish/$stop raised at its operating point.

The sweep verdicts (all 92 corpus models)

Everything not fixed above was triaged to model/bench characteristics: HiSIM-HV/SOI reject an all-terminals bench without COSUBNODE/COBCNODE=1 (by design, now with clean diagnostics); vbic_4T_et_cf floats internal nodes at RCX=0/RS=0 by design (use .option rshunt); EPFL-HEMT wants a realistic bias; FBH-HBT divides by its own out-of-range default Fb=0 in a ddt() (give fb>0 for transients) — reachable at all only thanks to the default fix.

Run

python3 verify_paramrange.py

Checks (13, ALL PASS): out-of-range defaults accepted with exact solutions (feature-off and feature-on conductances); given out-of-range values still rejected (exclusive range bound, exclude list, beyond-range); the hisimsoi noise crash reproducer now aborts cleanly (was SIGABRT); and the stock CMC diode_cmc from VA_TEST runs op/AC/noise at default parameters with a positive noise spectrum. Checks 4–5 use the VA_TEST corpus and are skipped if it is absent.