Hold a stateful solver

Geometry hosts such as eOn call Optimizer::step() once per outer iteration. rgmin_minimize is a full solve. The session type rgmin_solver_t (Rust Solver) is the matching handle: create once, step many times, free at the end.

Rust

use eindir_core::objectives::Rosenbrock;
use ndarray::array;
use rgmin::{Accept, Control, Method, QnStep, Solver};

let obj = Rosenbrock::<2>::new();
let mut x = array![-1.2, 1.0];
let mut solver = Solver::new(Method::lbfgs(), Control::default(), 2)
    .with_gtol(1e-8);
solver.set_qn_step(QnStep::Newton);
solver.set_accept(Accept::None);
let report = solver.step(&obj, &mut x).unwrap();

step is one outer iteration. step_hess / step_hess_fg take a host Hessian. forget drops pair history, conjugacy, and moments. set_atom_maxmove is the eOn per-atom clip. set_project_rigid projects translations and rotations on isolated clusters.

C

#include "xts.h"

rgmin_control_t ctrl = { .maxiter = 200, .gtol = 1e-8, .istep = 1.0, .memory = 8 };
rgmin_solver_t *s = rgmin_solver_create(RGMIN_LBFGS, &ctrl, n);
rgmin_report_t report;
while (!done) {
    rgmin_solver_set_maxmove(s, max_move);
    rgmin_solver_set_qn_step(s, RGMIN_QN_NEWTON);
    rgmin_solver_set_accept(s, RGMIN_ACCEPT_NONE);
    rgmin_solver_step_hess_fg(s, evalgrad, hess, user, x, &report);
}
rgmin_solver_free(s);

Callbacks are arguments of each step, not stored on the handle. rgmin_solver_step_fg / rgmin_solver_step_hess_fg take one fused (f, g) callback so a host that already bills energy and forces together is not asked twice.

Setters

Setter	Role
set_qn_step	Two-loop, Newton, or RFO when a host Hessian is present
set_accept	none / energy / nonmonotone
set_atom_maxmove	Per-atom clip (preferred over a Euclidean cap)
set_project_rigid	Drop rigid modes on isolated clusters
set_extra_updates	Al-Baali extra L-BFGS pairs
set_cautious	Li–Fukushima pair filter
set_highs	Feasible-set QP; returns 1 without --features highs
set_manifold	Embedded geometry; rigid_quotient for 3N clusters
set_masses	Per-atom masses for mw_rigid (Page–McIver)

When to use rgmin_minimize instead

Scripts that want a cold-start solve to gtol still call rgmin_minimize / minimize_method. Hopping chains that own the pair history hold Lbfgs directly (see embed in anneal).