otspot-core 0.4.0

Core implementation for otspot (LP/QP/MIP solver) — published as a dependency of the otspot facade
Documentation 
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//! Step 5: bounds tightening from implied row activity.

use super::state::{PostsolveStep, PresolveState, PresolveStatus};
use crate::presolve::activity::propagate_row_bounds;
use crate::tolerances::ZERO_TOL;

pub(super) fn step5_bounds_tightening(
    st: &mut PresolveState,
    new_fixed: &mut usize,
    deadline: Option<std::time::Instant>,
) -> Result<(), PresolveStatus> {
    let m = st.b.len();
    for i in 0..m {
        if deadline.is_some_and(|d| std::time::Instant::now() >= d) {
            return Ok(());
        }
        if st.removed_rows[i] {
            continue;
        }
        let ct = st.constraint_types[i];
        let entries = st.active_row_entries(i);
        if entries.is_empty() {
            continue;
        }

        let updates = propagate_row_bounds(
            &entries, &st.bounds, ct, st.b[i],
            // LP presolve passes int_mask=None; acceptance is unconditional
            // (aggressive tightening, unlike MIP presolve which must not cut off
            // integer solutions).
            None,
        )
        .ok_or(PresolveStatus::Infeasible)?;

        for (j, new_lb, new_ub) in updates {
            st.postsolve_stack.push(PostsolveStep::BoundsTightened);
            st.bounds[j] = (new_lb, new_ub);
            if (new_lb - new_ub).abs() < ZERO_TOL {
                *new_fixed += 1;
            }
        }
    }
    Ok(())
}