diff --git a/_posts/2024-06-30-chalopin24a.md b/_posts/2024-06-30-chalopin24a.md index e4d46fe..51c3fd0 100644 --- a/_posts/2024-06-30-chalopin24a.md +++ b/_posts/2024-06-30-chalopin24a.md @@ -8,23 +8,25 @@ abstract: 'Recently, Kirkpatrick et al. [ALT 2019] and Fallat et al. [JMLR 20 set $T(C)$ of examples to each concept $C \in \mathcal{C}$. A teaching map is non-clashing if no pair of concepts are consistent with the union of their teaching sets. The size of a non-clashing teaching map (NCTM) $T$ is the maximum size of a teaching - set $T(C)$, $C \in \mathcal{C}$. The non-clashing teaching dimension $NCTD(\mathcal{C})$ - of $\mathcal{C}$ is the minimum size of an NCTM for $\mathcal{C}$. NCTM$^+$ and - NCTD$^+(\mathcal{C})$ are defined analogously, except the teacher may only use positive - examples. We study NCTMs and NCTM$^+$s for the concept class $\mathcal{B}(G)$ consisting - of all balls of a graph $G$. We show that the associated decision problem \textsc{B-NCTD$^+$} - for NCTD$^+$ is \textsf{NP}-complete in split, co-bipartite, and bipartite graphs. - Surprisingly, we even prove that, unless the \textsf{ETH} fails, \textsc{B-NCTD$^+$} + set $T(C)$, $C \in \mathcal{C}$. The non-clashing teaching dimension $\text{NCTD}(\mathcal{C})$ + of $\mathcal{C}$ is the minimum size of an NCTM for $\mathcal{C}$. $\text{NCTM}^+$ and + $\text{NCTD}^+(\mathcal{C})$ are defined analogously, except the teacher may only use positive + examples. + + We study NCTMs and $\text{NCTM}^+\text{s}$ for the concept class $\mathcal{B}(G)$ consisting + of all balls of a graph $G$. We show that the associated decision problem $\text{B-NCTD}^+$ + for $\text{NCTD}^+$ is NP-complete in split, co-bipartite, and bipartite graphs. + Surprisingly, we even prove that, unless the ETH fails, $\text{B-NCTD}^+$ does not admit an algorithm running in time $2^{2^{o(\mathtt{vc})}}\cdot n^{\mathcal{O}(1)}$, nor a kernelization algorithm outputting a kernel with $2^{o(\mathtt{vc})}$ vertices, - where $\mathtt{vc}$ is the vertex cover number of $G$. These are extremely rare - results: it is only the second (fourth, resp.) problem in \textsf{NP} to admit such - a double-exponential lower bound parameterized by $\mathtt{vc}$ (treewidth, resp.), - and only one of very few problems to admit such an \textsf{ETH}-based conditional - lower bound on the number of vertices in a kernel. We complement these lower bounds - with matching upper bounds. For trees, interval graphs, cycles, and trees of cycles, - we derive NCTM$^+$s or NCTMs for $\mathcal{B}(G)$ of size proportional to its VC-dimension. - For Gromov-hyperbolic graphs, we design an approximate NCTM$^+$ for $\mathcal{B}(G)$ + where $\mathtt{vc}$ is the vertex cover number of $G$. We complement these lower bounds + with matching upper bounds. These are extremely rare + results: it is only the second problem in NP to admit such + a tight double-exponential lower bound parameterized by $\mathtt{vc}$, + and only one of very few problems to admit such an ETH-based conditional + lower bound on the number of vertices in a kernel. For trees, interval graphs, cycles, and trees of cycles, + we derive $\text{NCTM}^+\text{s}$ or NCTMs for $\mathcal{B}(G)$ of size proportional to its VC-dimension. + For Gromov-hyperbolic graphs, we design an approximate $\text{NCTM}^+$ for $\mathcal{B}(G)$ of size $2$, in which only pairs of balls with Hausdorff distance larger than some constant must satisfy the non-clashing condition.' layout: inproceedings