It is well known that the containment problem (as well as the equivalence problem) for semilinear sets is $log$-complete in $Pi_2^p$. It had been shown quite recently that already the containment problem for multi-dimensional linear sets is $log$-complete in $Pi_2^p$ (where hardness even holds for a unary encoding of the numerical input parameters). In this paper, we show that already the containment problem for $1$-dimensional linear sets (with binary encoding of the numerical input parameters) is $log$-hard (and therefore also $log$-complete) in $Pi_2^p$. However, combining both restrictions (dimension $1$ and unary encoding), the problem becomes solvable in polynomial time.
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