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Limits model ​

Problem ​

A supercell, a porosity grid or a Hessian is expensive before a single atom or grid point exists. The estimate must be arithmetic and happen before allocation so the caller can be warned or refused with a concrete alternative.

Model ​

Limits model

Every budget has a soft and a hard limit. Standard is the 8 GB-class table; Generous doubles both; WarnOnly keeps the soft limit and removes the hard one. The check returns Verdict { level, estimate, sentence }:

  • ok — estimate at or below the soft limit, empty sentence;
  • warn — over soft and (if present) at or below hard;
  • refuse — over hard.

The sentence always names the estimate and what would fit (a smaller cube, a coarser grid, or fewer atoms).

Estimates ​

  • Drawn atoms: n_atoms * product(range_hi - range_lo).
  • Supercell: n_atoms * |det P|.
  • Grid: round(length / spacing) per axis, minimum 8, product.
  • Phonons: the supercell estimate.
  • Analytic Hessian: the free atom count, with the memory note 13 MiB * n_atoms.

Validation ​

The table and profiles are covered by crates/xtalforge-core/tests/limits.rs. The surfaces are checked by the Python and WASM tests. The carbon, nanotube, graphene, phonon and Hessian budgets are fixed in the table; a caller decides which generic check (check_supercell, check_grid, check_phonons, check_hessian) matches its allocation.