Function floored_alphas 

pub fn floored_alphas(
    cq: &IpoptCqHandle,
    delta: &IteratesVector,
    mu: Number,
    gamma: Number,
    tau: Number,
) -> Option<(Number, Number)>

Returns Some((alpha_p, alpha_d)) or None when a block is not a dense vector (restoration’s compound iterates); the caller then keeps the ordinary τ rule.