Ramon benchmark for Z3
-
Job description: 
Job tag: qf-nia-small-pr9391-s-suppress
Runner: rise-runner-1
Z3 repo: 1arie1/z3
Z3 commit: e1e6ee3efabdfbd2ba63742a8656a12cb42b45a9
Z3 branch: ag/mono-sandwich
Z3 options: "-T:30 smt.arith.nl.monomial_sandwich=true smt.arith.nl.order.binomial_sign=false"
Z3 inputs: inputs/QF_NIA_small
Z3 commit message: Add McCormick box-corner tangent points (Opportunity 2 from ord-binom doc)

When enabled via arith.nl.tangents.box_corners (default off, sub-flag of
arith.nl.tangents), tangent_imp::get_points selects m_a, m_b at the corners
of the bound box [x_lo, x_hi] × [y_lo, y_hi] instead of the model-centered
points val(x) ± delta. The selection follows the classical McCormick
under/over envelope:

  - m_below=true (under-approximation):
      m_a = (x_lo, y_lo),  m_b = (x_hi, y_hi)
  - m_below=false (over-approximation):
      m_a = (x_lo, y_hi),  m_b = (x_hi, y_lo)

The existing generate_plane already produces the McCormick linear form
xy ≷ pl.y·x + pl.x·y − pl.x·pl.y at any chosen point pl. push_point is
skipped in box-corner mode: corners are extremes, so doubling the offset
moves out of the box and would invalidate the McCormick property.

Falls back to the existing model-driven point selection when either factor
has an unbounded side or the box is degenerate (single-point in a
dimension).

Soundness — non-strict inequality at corners. The classical model-driven
flow uses pl strictly in the interior of the box, so generate_plane emits
xy > T (strict). At the box corners the tangent meets the surface along
the box's edges (xy = T when x = pl.x or y = pl.y), so the strict
inequality is violated by any model with x at the box boundary. A new
m_pl_strict_interior member, set false on a successful set_box_corners(),
switches generate_plane's emission to ≥/≤ (non-strict). The model-driven
path keeps strict — its push_point + plane_is_correct_cut chain already
guarantees pl is interior.

Validated via smt.arith.validate=true: 0 validate_conflict() failures
across the 32-leaf test corpus with box_corners=true.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
