not overlap. If the positions have to be decided, then both the pad and the location on the pad have to be decided for each stockpile.

-   Precedence constraints between stockpiles have to be observed or not. When precedence constraints have to be observed, the reclaim sequence of the stockpiles is completely specified. That is, the precedence constraints form a chain involving all the stockpiles.

The goal in all settings is to reclaim all stockpiles and to minimize the time at which both reclaimers have returned to their original positions.

We use the following notation. When the positions of the stockpiles are given, we have two sets $J_1 = \{1, \ldots, n_1\}$ and $J_2 =
\{n_1+1, \ldots, n\}$ of stockpiles located on the two identical and opposite pads $P_1$ and $P_2$. We represent a pad by segment $[0,L]$, with $L$ being the length of the pad. Stockpile $j \in J_1$ occupies a segment $[l_j, r_j]$ on pad $P_1$ ($0 \leqslant l_j < r_j \leq
L$). Similarly, stockpile $j \in J_2$ occupies a segment $[l_j,
r_j]$ on pad $P_2$. Stockpiles cannot overlap on the same pad and we assume that $r_j \leqslant l_{j+1}$ for $j \in \{1, \ldots, n_1-1\}$ and for 