Function IpoptSolverParametricStep 

#[unsafe(no_mangle)]
pub unsafe extern "C" fn IpoptSolverParametricStep(
    solver: IpoptSolver,
    n_pins: Index,
    pin_indices: *const Index,
    deltas: *const Number,
    dx_out: *mut Number,
) -> Bool

First-order parametric step Δx ≈ ∂x*/∂p · Δp. pin_indices is n_pins Index values (0-based indices into g(x)); deltas is the parameter perturbation Δp of the same length; dx_out is the n-long primal step output (length matches the problem’s n).

Returns TRUE on success, FALSE if no converged factor, invalid indices, or the sensitivity computation fails.

Safety

pin_indices and deltas must point to n_pins valid elements; dx_out must point to at least n Number slots (n from the underlying IpoptProblem).