Enhancement-887: an option given while a run is paused is applied or held, and said — option maxord=3 or option klu before resume crashed a run started by run, and a run started by tran ignored every option without a word

Enhancement-887: an option given while a run is paused is applied or held, and said — option maxord=3 or option klu before resume crashed a run started by run, and a run started by tran ignored every option without a word

Scope: N5 of the
transient stress campaign of 2026-10-12.

ngspice:

• frontend/spiceif.c, if_run: the options a run starts with are kept; on resume the ones
  changed since are applied or held, with a note.
• include/ngspice/ftedefs.h: ci_runopts.
• frontend/runcoms2.c: freed with the circuit.

examples/transnotes_examples/ (new, shared with E-885,
E-886 and E-888). ngspice only.

Suites:

• transnotes_examples: [5] to [8] are this enhancement's,
  11 of 11 per solver. On the E-883 binaries [5] to [8] fail.
• checkpoint, ckorder, resumebreak, stagedslots, autosave, idtassert and writemc
  pass.
• The full sweep: 587 of 587.

What was wrong

option writes the default task's options. What a paused run did with them depended on how the
run started.

• Started by run (the deck's own .tran): the run's task IS the default task, and
  CKTdoJob copies every option from it again at a resume. A new method or maxord met history
  slots the run had not allocated, and option klu met a matrix built for Sparse:

  • option maxord=3, option method=gear maxord=4 dynorder: a segmentation fault in CAPload;
  • option klu: one in NIiter.

  option method=gear switched the method mid-run, and option reltol=1e-6 was taken. None of
  it was said.

• Started by tran (from .control): the run has its own copy of the task, made at the
  command, and nothing given during the pause reached it. Method, maxord, dynorder, the
  solver and reltol all gave the uninterrupted run's 1 346 iterations, without a word. This is
  what the campaign saw: its sessions started their runs with tran.

The change

Both routes now resume alike. When a run starts, if_run keeps a copy of its options; at
resume it compares the default task, where option writes, with that copy. So an option set
before the run is not reported, and only what changed during the pause is.

• Taken by the resumed run: the options read afresh at every step. These are reltol,
  abstol, vntol, chgtol, trtol, xmu, trgamma, itl4, gmin, gshunt, pivtol,
  pivrel, absdv, reldv, bypass, and the Newton aids nodedamping, linesearch and
  trustregion.

  Note: the resumed run takes reltol = 1e-06 and trtol = 0.1, given during the pause.
  

• Held at the run's values: the options the run was built on. These are the method,
  maxord, ordfix, dynorder, temp, tnom, cshunt and the solver with its klu_*
  settings. They take effect from the next analysis.

  Note: method = gear, maxord = 4 and dynorder on, given during the pause, take effect from the next analysis; the resumed run keeps method = trap, maxord = 2 and dynorder off, which it was built on.
  

  On the run route the default task gets the values given back after the resumed run, for the
  next analysis. A held option is named once, however many pauses follow.

A checkpoint's continuation (loadstate) starts from the options set at that moment, which
E-879 built its circuit on. It compares nothing, and is the start a later
pause compares against.

Measured

On an RC with an inductor, stopped at 1 µs of 4 µs, with delete all before the resume:

given during the pause	E-883, run	E-883, tran	E-887, both
maxord=3	segmentation fault	kept, silently	kept, named; 4.44486e-7, the uninterrupted value
klu	segmentation fault	kept, silently	kept, named
method=gear maxord=4 dynorder	segmentation fault	kept, silently	kept, named
method=gear	switched mid-run, silently	kept, silently	kept, named
reltol=1e-6 trtol=0.1	taken (3 385 iterations), silently	ignored (887)	taken on both, named; 4.51376e-7

The next analysis after the resumed run, with method=gear maxord=3 klu given during the pause,
ends at 4.212264e-7 on both routes. That is the value of a fresh run with those options.

The checks

transnotes_examples:

• [5] A run started by run, given maxord=3, the other solver, and
  method=gear maxord=4 dynorder during a pause, resumes without a crash. It names each with the
  value it keeps, and ends where the uninterrupted run ends.
• [6] A run started by tran names and keeps them the same way.
• [7] reltol and trtol given during the pause are taken on both routes, which say so and
  end at the same value.
• [8] The options held for the resumed run take effect at the next analysis, on both routes.

Write-up: enhancements_doc/Enhancement-887.md