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Preference-Based Batch and Sequential Teaching: Towards a Unified View of Models Farnam Mansouri Yuxin Chen Ara Vartanian Xiaojin Zhu Adish Singla Max Planck Institute for Software Systems (MPI-SWS) University of Chicago University of Wisconsin-Madison Preference-Based Batch and Sequential Teaching: Towards a Unified View of Models Farnam Mansouri Yuxin Chen Ara Vartanian Xiaojin Zhu Adish Singla Max Planck Institute for Software Systems (MPI-SWS) University of Chicago University of Wisconsin-Madison Algorithmic Teaching Learner Teacher X , H,h t X , H,h teacher selects , and provides x t ,h (x t ) h t learner updates teacher receives as feedback h t x t Canonical Example Discrete points on a line X = {1, 2,...,n} 1 2 ... h n h (x)=1 h (x)=0 Threshold classifier h(x) = 1 i↵ x h where h 2{1, 2,...,n} Complexity of passive learning: Opnq; active learning: Oplogpnqq; teaching: 2. Interaction Protocol 1: learner’s initial version space is H 0 H and learner starts from h 0 P H 2: for t 1, 2, 3,... do 3: teacher provides z t “px t ,h px t qq 4: learner updates H t H t´1 X Hptz t uq; picks h t P H t 5: teacher receives h t as feedback from the learner 6: if h t h then teaching process terminates h h t H({z t }) H t-1 H t h t-1 h Complexity Measures Notions Description TD classical worst-case teaching complexity RTD notion of TD when teaching a collaborative learner NCTD strongest notion of TD that respects collusion-freeness Local-PBTD teaching complexity of a weak sequential model Research Questions Is there a framework unifying different notions of TD’s? Can we identify models with teaching complexity linear in the Vapnik–Chervonenkis dimension VCD? Our Contributions A novel framework capturing the teaching process via preference functions Σ, where each function σ P Σ induces a teacher-learner pair. Our main results are as follows: We show that existing batch models correspond to spe- cific families of σ functions in our framework. We identify sequential models with teaching complexity linear in the VCD of the hypothesis class. We provide a constructive procedure to find σ functions with low teaching complexity. Σ const Σ global Σ gvs Σ local Σ lvs Table 1: Main Resuls Families Σ const Σ global Σ gvs Σ local Σ lvs Reduction TD RTD NCTD Local-PBTD Complexity Results OpVCD 2 q OpVCD 2 q OpVCD 2 q OpVCDq [GK95] [Zil+11] [KSZ19] [Che+18] Learner’s Preference Function A preference function σ : H ˆ 2 H ˆ H Ñ R models how a learner navigates in the version space as it receives teaching examples (line 4 of Interaction Protocol ): h t P arg min h 1 PH t σ ph 1 ; H t ,h t´1 q. Teaching Complexity Σ-TD Teaching Dimension for a Preference Function Fix X , H, and learner’s initial hypothesis h 0 . Let D X ,H,h 0 pσ, h q be the worst-case optimal cost for steering the learner from h 0 to h for some preference function σ . Then, the teaching dimension w.r.t. σ is defined as the worst-case optimal cost for teaching any target h : TD X ,H,h 0 pσ q“ max h D X ,H,h 0 pσ, h q. Teaching Dimension for a Family of Preference Functions We define the teaching dimension for a family Σ as the teaching dimension w.r.t. the best σ P Σ: Σ-TD X ,H,h 0 min σPΣ TD X ,H,h 0 pσ q. Collusion-free Preference Functions Definition 1 (Collusion-free teaching [GM96] (batch setting)) A learner outputting hypothesis h will not change its output if given additional information consistent with h. Definition 2 (Collusion-free preference (this paper)) If h is the only hypothesis in the most preferred set defined by σ , then the learner will stay at h if additional information received by the learner is consistent with h. We study preference functions that are collusion-free as per Definition 2: Σ CF “tσ | σ is collusion-freeu. Preference-based Teaching Models Batch models: const “tσ P Σ CF |Dc P R, s.t. @h 1 , H, h, σ ph 1 ; H, hq“ cu global “tσ P Σ CF |D g : H Ñ R, s.t. @h 1 ,H,h, σ ph 1 ; H, hq“ g ph 1 qu gvs “tσ P Σ CF |D g : H ˆ 2 H Ñ R, s.t. @h 1 , H, h, σ ph 1 ; H, hq“ g ph 1 ,H qu Sequential models: local “tσ P Σ CF |D g : H ˆ H Ñ R, s.t. @h 1 , H, h, σ ph 1 ; H, hq“ g ph 1 ,hqu lvs “tσ P Σ CF |D g : H ˆ 2 H ˆ H Ñ R, s.t. @h 1 , H, h, σ ph 1 ; H, hq“ g ph 1 ,H,hqu Teaching sequences with different preference functions for the Warmuth hypothesis class: H H H H H h x x 1 x 2 x 3 x 4 x 5 S const S global S gvs S local S lvs h 1 1 1 0 0 0 px 1 ,x 2 ,x 4 q px 1 ,x 2 q px 1 q px 1 q h 2 0 1 1 0 0 px 2 ,x 3 ,x 5 q px 2 ,x 3 q px 3 q px 2 q h 3 0 0 1 1 0 px 1 ,x 3 ,x 4 q px 3 ,x 4 q px 3 ,x 4 q px 3 q h 4 0 0 0 1 1 px 2 ,x 4 ,x 5 q px 4 ,x 5 q px 5 ,x 4 q px 4 q h 5 1 0 0 0 1 px 1 ,x 3 ,x 5 q px 1 ,x 5 q px 5 q px 5 q h 6 1 1 0 1 0 px 1 ,x 2 ,x 4 q px 2 ,x 4 q px 4 q px 3 q h 7 0 1 1 0 1 px 2 ,x 3 ,x 5 q px 3 ,x 5 q px 3 ,x 5 q px 4 q h 8 1 0 1 1 0 px 1 ,x 3 ,x 4 q px 1 ,x 4 q px 4 ,x 3 q px 5 q h 9 0 1 0 1 1 px 2 ,x 4 ,x 5 q px 2 ,x 5 q px 4 ,x 5 q px 1 q h 10 1 0 1 0 1 px 1 ,x 3 ,x 5 q px 1 ,x 3 q px 5 ,x 3 q px 2 q (a) The Warmuth hypothesis class and the corresponding teaching sequences (denoted by S ). h 1 @h 1 P H σ const ph 1 ; ¨, ¨q 0 σ global ph 1 ; ¨, ¨q (b) σ const and σ global hzh 1 h 1 h 2 h 3 h 4 h 5 h 6 h 7 h 8 h 9 h 10 σ local ph 1 ; ¨,h h 1 q 0 2 4 4 2 1 3 3 3 3 ... (c) σ local representing the Hamming distance between h 1 and h. Main Results Reduction to existing notions of TD’s (see Table 1). Proving Σ lvs -TD X ,H,h 0 O ` VCDpH, X q ˘ via a constructive procedure. Key Ideas for Constructing σ P Σ lvs with TD X ,H,h 0 pσ q“ OpVCDq Introducing a new notion of compact distinguishable set. Partitioning the hypothesis class into subsets of hypothesis classes with lower VCD using the compact distinguishable set. Recursively applying the partitioning procedure to create the preference function σ . Discussions Designing σ functions for addressing the open question of whether RTD is linear in VCD. Designing teaching algorithms for sequential models. References [GK95] Sally A Goldman and Michael J Kearns. On the complexity of teaching. In: J. Comput. Syst. Sci 50.1 (1995), pp. 20–31. [Zil+11] Sandra Zilles, Steffen Lange, Robert Holte, and Martin Zinkevich. Models of cooperative teaching and learning. In: JMLR 12.Feb (2011), pp. 349–384. [KSZ19] David Kirkpatrick, Hans U. Simon, and Sandra Zilles. Optimal Collusion-Free Teaching. In: ALT. Vol. 98. 2019, pp. 506–528. [Che+18] Yuxin Chen, Adish Singla, Oisin Mac Aodha, Pietro Perona, and Yisong Yue. Understanding the role of adaptivity in machine teaching: The case of version space learners. In: NeurIPS. 2018, pp. 1476–1486. [GM96] Sally A Goldman and H David Mathias. Teaching a smarter learner. In: J. Comput. Syst. Sci 52.2 (1996), pp. 255–267.

Theorem 2 Neither of the families Preference-Based Batch ... · -lvs t˙P CF |Dg: H 2H HÑR;s.t. @h1;H;h;˙ph1;H;hq gph1;H;hqu Teaching sequences with di erent preference functions

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Page 1: Theorem 2 Neither of the families Preference-Based Batch ... · -lvs t˙P CF |Dg: H 2H HÑR;s.t. @h1;H;h;˙ph1;H;hq gph1;H;hqu Teaching sequences with di erent preference functions

Preference-Based Batch and Sequential Teaching: Towards a Unified View of Models

Farnam Mansouri† Yuxin Chen‡ Ara Vartanian‹ Xiaojin Zhu‹ Adish Singla†

†Max Planck Institute for Software Systems (MPI-SWS) ‡University of Chicago ‹University of Wisconsin-Madison

Preference-Based Batch and Sequential Teaching: Towards a Unified View of Models

Farnam Mansouri† Yuxin Chen‡ Ara Vartanian‹ Xiaojin Zhu‹ Adish Singla†

†Max Planck Institute for Software Systems (MPI-SWS) ‡University of Chicago ‹University of Wisconsin-Madison

Algorithmic Teaching

LearnerTeacher

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teacher selects , and provides xt, h⇤(xt)

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ht<latexit sha1_base64="MyjL8KJZcyk/u3ijeLcAQFoh7OY=">AAAB6nicbVBNS8NAEJ3Ur1q/oh69LBbBU0lE0GPRi8eK9gPaUDbbTbt0swm7E6GE/gQvHhTx6i/y5r9x2+agrQ8GHu/NMDMvTKUw6HnfTmltfWNzq7xd2dnd2z9wD49aJsk0402WyER3Qmq4FIo3UaDknVRzGoeSt8Px7cxvP3FtRKIecZLyIKZDJSLBKFrpYdTHvlv1at4cZJX4BalCgUbf/eoNEpbFXCGT1Jiu76UY5FSjYJJPK73M8JSyMR3yrqWKxtwE+fzUKTmzyoBEibalkMzV3xM5jY2ZxKHtjCmOzLI3E//zuhlG10EuVJohV2yxKMokwYTM/iYDoTlDObGEMi3srYSNqKYMbToVG4K//PIqaV3UfK/m319W6zdFHGU4gVM4Bx+uoA530IAmMBjCM7zCmyOdF+fd+Vi0lpxi5hj+wPn8AVjcjdM=</latexit><latexit sha1_base64="MyjL8KJZcyk/u3ijeLcAQFoh7OY=">AAAB6nicbVBNS8NAEJ3Ur1q/oh69LBbBU0lE0GPRi8eK9gPaUDbbTbt0swm7E6GE/gQvHhTx6i/y5r9x2+agrQ8GHu/NMDMvTKUw6HnfTmltfWNzq7xd2dnd2z9wD49aJsk0402WyER3Qmq4FIo3UaDknVRzGoeSt8Px7cxvP3FtRKIecZLyIKZDJSLBKFrpYdTHvlv1at4cZJX4BalCgUbf/eoNEpbFXCGT1Jiu76UY5FSjYJJPK73M8JSyMR3yrqWKxtwE+fzUKTmzyoBEibalkMzV3xM5jY2ZxKHtjCmOzLI3E//zuhlG10EuVJohV2yxKMokwYTM/iYDoTlDObGEMi3srYSNqKYMbToVG4K//PIqaV3UfK/m319W6zdFHGU4gVM4Bx+uoA530IAmMBjCM7zCmyOdF+fd+Vi0lpxi5hj+wPn8AVjcjdM=</latexit><latexit sha1_base64="MyjL8KJZcyk/u3ijeLcAQFoh7OY=">AAAB6nicbVBNS8NAEJ3Ur1q/oh69LBbBU0lE0GPRi8eK9gPaUDbbTbt0swm7E6GE/gQvHhTx6i/y5r9x2+agrQ8GHu/NMDMvTKUw6HnfTmltfWNzq7xd2dnd2z9wD49aJsk0402WyER3Qmq4FIo3UaDknVRzGoeSt8Px7cxvP3FtRKIecZLyIKZDJSLBKFrpYdTHvlv1at4cZJX4BalCgUbf/eoNEpbFXCGT1Jiu76UY5FSjYJJPK73M8JSyMR3yrqWKxtwE+fzUKTmzyoBEibalkMzV3xM5jY2ZxKHtjCmOzLI3E//zuhlG10EuVJohV2yxKMokwYTM/iYDoTlDObGEMi3srYSNqKYMbToVG4K//PIqaV3UfK/m319W6zdFHGU4gVM4Bx+uoA530IAmMBjCM7zCmyOdF+fd+Vi0lpxi5hj+wPn8AVjcjdM=</latexit><latexit sha1_base64="MyjL8KJZcyk/u3ijeLcAQFoh7OY=">AAAB6nicbVBNS8NAEJ3Ur1q/oh69LBbBU0lE0GPRi8eK9gPaUDbbTbt0swm7E6GE/gQvHhTx6i/y5r9x2+agrQ8GHu/NMDMvTKUw6HnfTmltfWNzq7xd2dnd2z9wD49aJsk0402WyER3Qmq4FIo3UaDknVRzGoeSt8Px7cxvP3FtRKIecZLyIKZDJSLBKFrpYdTHvlv1at4cZJX4BalCgUbf/eoNEpbFXCGT1Jiu76UY5FSjYJJPK73M8JSyMR3yrqWKxtwE+fzUKTmzyoBEibalkMzV3xM5jY2ZxKHtjCmOzLI3E//zuhlG10EuVJohV2yxKMokwYTM/iYDoTlDObGEMi3srYSNqKYMbToVG4K//PIqaV3UfK/m319W6zdFHGU4gVM4Bx+uoA530IAmMBjCM7zCmyOdF+fd+Vi0lpxi5hj+wPn8AVjcjdM=</latexit>

learner updates

teacher receives as feedbackht<latexit sha1_base64="MyjL8KJZcyk/u3ijeLcAQFoh7OY=">AAAB6nicbVBNS8NAEJ3Ur1q/oh69LBbBU0lE0GPRi8eK9gPaUDbbTbt0swm7E6GE/gQvHhTx6i/y5r9x2+agrQ8GHu/NMDMvTKUw6HnfTmltfWNzq7xd2dnd2z9wD49aJsk0402WyER3Qmq4FIo3UaDknVRzGoeSt8Px7cxvP3FtRKIecZLyIKZDJSLBKFrpYdTHvlv1at4cZJX4BalCgUbf/eoNEpbFXCGT1Jiu76UY5FSjYJJPK73M8JSyMR3yrqWKxtwE+fzUKTmzyoBEibalkMzV3xM5jY2ZxKHtjCmOzLI3E//zuhlG10EuVJohV2yxKMokwYTM/iYDoTlDObGEMi3srYSNqKYMbToVG4K//PIqaV3UfK/m319W6zdFHGU4gVM4Bx+uoA530IAmMBjCM7zCmyOdF+fd+Vi0lpxi5hj+wPn8AVjcjdM=</latexit><latexit sha1_base64="MyjL8KJZcyk/u3ijeLcAQFoh7OY=">AAAB6nicbVBNS8NAEJ3Ur1q/oh69LBbBU0lE0GPRi8eK9gPaUDbbTbt0swm7E6GE/gQvHhTx6i/y5r9x2+agrQ8GHu/NMDMvTKUw6HnfTmltfWNzq7xd2dnd2z9wD49aJsk0402WyER3Qmq4FIo3UaDknVRzGoeSt8Px7cxvP3FtRKIecZLyIKZDJSLBKFrpYdTHvlv1at4cZJX4BalCgUbf/eoNEpbFXCGT1Jiu76UY5FSjYJJPK73M8JSyMR3yrqWKxtwE+fzUKTmzyoBEibalkMzV3xM5jY2ZxKHtjCmOzLI3E//zuhlG10EuVJohV2yxKMokwYTM/iYDoTlDObGEMi3srYSNqKYMbToVG4K//PIqaV3UfK/m319W6zdFHGU4gVM4Bx+uoA530IAmMBjCM7zCmyOdF+fd+Vi0lpxi5hj+wPn8AVjcjdM=</latexit><latexit sha1_base64="MyjL8KJZcyk/u3ijeLcAQFoh7OY=">AAAB6nicbVBNS8NAEJ3Ur1q/oh69LBbBU0lE0GPRi8eK9gPaUDbbTbt0swm7E6GE/gQvHhTx6i/y5r9x2+agrQ8GHu/NMDMvTKUw6HnfTmltfWNzq7xd2dnd2z9wD49aJsk0402WyER3Qmq4FIo3UaDknVRzGoeSt8Px7cxvP3FtRKIecZLyIKZDJSLBKFrpYdTHvlv1at4cZJX4BalCgUbf/eoNEpbFXCGT1Jiu76UY5FSjYJJPK73M8JSyMR3yrqWKxtwE+fzUKTmzyoBEibalkMzV3xM5jY2ZxKHtjCmOzLI3E//zuhlG10EuVJohV2yxKMokwYTM/iYDoTlDObGEMi3srYSNqKYMbToVG4K//PIqaV3UfK/m319W6zdFHGU4gVM4Bx+uoA530IAmMBjCM7zCmyOdF+fd+Vi0lpxi5hj+wPn8AVjcjdM=</latexit><latexit sha1_base64="MyjL8KJZcyk/u3ijeLcAQFoh7OY=">AAAB6nicbVBNS8NAEJ3Ur1q/oh69LBbBU0lE0GPRi8eK9gPaUDbbTbt0swm7E6GE/gQvHhTx6i/y5r9x2+agrQ8GHu/NMDMvTKUw6HnfTmltfWNzq7xd2dnd2z9wD49aJsk0402WyER3Qmq4FIo3UaDknVRzGoeSt8Px7cxvP3FtRKIecZLyIKZDJSLBKFrpYdTHvlv1at4cZJX4BalCgUbf/eoNEpbFXCGT1Jiu76UY5FSjYJJPK73M8JSyMR3yrqWKxtwE+fzUKTmzyoBEibalkMzV3xM5jY2ZxKHtjCmOzLI3E//zuhlG10EuVJohV2yxKMokwYTM/iYDoTlDObGEMi3srYSNqKYMbToVG4K//PIqaV3UfK/m319W6zdFHGU4gVM4Bx+uoA530IAmMBjCM7zCmyOdF+fd+Vi0lpxi5hj+wPn8AVjcjdM=</latexit>

xt<latexit sha1_base64="NHiqf4cvCuRDOUL/QX8cKwAbK3c=">AAAB6nicbVBNS8NAEJ3Ur1q/qh69LBbBU0lEqMeiF48V7Qe0oWy2m3bpZhN2J2IJ/QlePCji1V/kzX/jts1BWx8MPN6bYWZekEhh0HW/ncLa+sbmVnG7tLO7t39QPjxqmTjVjDdZLGPdCajhUijeRIGSdxLNaRRI3g7GNzO//ci1EbF6wEnC/YgOlQgFo2il+6c+9ssVt+rOQVaJl5MK5Gj0y1+9QczSiCtkkhrT9dwE/YxqFEzyaamXGp5QNqZD3rVU0YgbP5ufOiVnVhmQMNa2FJK5+nsio5ExkyiwnRHFkVn2ZuJ/XjfF8MrPhEpS5IotFoWpJBiT2d9kIDRnKCeWUKaFvZWwEdWUoU2nZEPwll9eJa2LqudWvbvLSv06j6MIJ3AK5+BBDepwCw1oAoMhPMMrvDnSeXHenY9Fa8HJZ47hD5zPH3E8jeM=</latexit><latexit sha1_base64="NHiqf4cvCuRDOUL/QX8cKwAbK3c=">AAAB6nicbVBNS8NAEJ3Ur1q/qh69LBbBU0lEqMeiF48V7Qe0oWy2m3bpZhN2J2IJ/QlePCji1V/kzX/jts1BWx8MPN6bYWZekEhh0HW/ncLa+sbmVnG7tLO7t39QPjxqmTjVjDdZLGPdCajhUijeRIGSdxLNaRRI3g7GNzO//ci1EbF6wEnC/YgOlQgFo2il+6c+9ssVt+rOQVaJl5MK5Gj0y1+9QczSiCtkkhrT9dwE/YxqFEzyaamXGp5QNqZD3rVU0YgbP5ufOiVnVhmQMNa2FJK5+nsio5ExkyiwnRHFkVn2ZuJ/XjfF8MrPhEpS5IotFoWpJBiT2d9kIDRnKCeWUKaFvZWwEdWUoU2nZEPwll9eJa2LqudWvbvLSv06j6MIJ3AK5+BBDepwCw1oAoMhPMMrvDnSeXHenY9Fa8HJZ47hD5zPH3E8jeM=</latexit><latexit sha1_base64="NHiqf4cvCuRDOUL/QX8cKwAbK3c=">AAAB6nicbVBNS8NAEJ3Ur1q/qh69LBbBU0lEqMeiF48V7Qe0oWy2m3bpZhN2J2IJ/QlePCji1V/kzX/jts1BWx8MPN6bYWZekEhh0HW/ncLa+sbmVnG7tLO7t39QPjxqmTjVjDdZLGPdCajhUijeRIGSdxLNaRRI3g7GNzO//ci1EbF6wEnC/YgOlQgFo2il+6c+9ssVt+rOQVaJl5MK5Gj0y1+9QczSiCtkkhrT9dwE/YxqFEzyaamXGp5QNqZD3rVU0YgbP5ufOiVnVhmQMNa2FJK5+nsio5ExkyiwnRHFkVn2ZuJ/XjfF8MrPhEpS5IotFoWpJBiT2d9kIDRnKCeWUKaFvZWwEdWUoU2nZEPwll9eJa2LqudWvbvLSv06j6MIJ3AK5+BBDepwCw1oAoMhPMMrvDnSeXHenY9Fa8HJZ47hD5zPH3E8jeM=</latexit><latexit sha1_base64="NHiqf4cvCuRDOUL/QX8cKwAbK3c=">AAAB6nicbVBNS8NAEJ3Ur1q/qh69LBbBU0lEqMeiF48V7Qe0oWy2m3bpZhN2J2IJ/QlePCji1V/kzX/jts1BWx8MPN6bYWZekEhh0HW/ncLa+sbmVnG7tLO7t39QPjxqmTjVjDdZLGPdCajhUijeRIGSdxLNaRRI3g7GNzO//ci1EbF6wEnC/YgOlQgFo2il+6c+9ssVt+rOQVaJl5MK5Gj0y1+9QczSiCtkkhrT9dwE/YxqFEzyaamXGp5QNqZD3rVU0YgbP5ufOiVnVhmQMNa2FJK5+nsio5ExkyiwnRHFkVn2ZuJ/XjfF8MrPhEpS5IotFoWpJBiT2d9kIDRnKCeWUKaFvZWwEdWUoU2nZEPwll9eJa2LqudWvbvLSv06j6MIJ3AK5+BBDepwCw1oAoMhPMMrvDnSeXHenY9Fa8HJZ47hD5zPH3E8jeM=</latexit>

Canonical Example

Discrete points on a line

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h⇤(x) = 1<latexit sha1_base64="bJO/yx8i5AStgfi/Tem5b15rC+s=">AAAB73icbVBNSwMxEJ2tX7V+VT16CRaheii7IuhFKHrxWMF+QLuWbJptQ5PsmmTFsvRPePGgiFf/jjf/jWm7B219MPB4b4aZeUHMmTau++3klpZXVtfy64WNza3tneLuXkNHiSK0TiIeqVaANeVM0rphhtNWrCgWAafNYHg98ZuPVGkWyTsziqkvcF+ykBFsrNQa3J+Un44vvW6x5FbcKdAi8TJSggy1bvGr04tIIqg0hGOt254bGz/FyjDC6bjQSTSNMRniPm1bKrGg2k+n947RkVV6KIyULWnQVP09kWKh9UgEtlNgM9Dz3kT8z2snJrzwUybjxFBJZovChCMTocnzqMcUJYaPLMFEMXsrIgOsMDE2ooINwZt/eZE0TiueW/Fuz0rVqyyOPBzAIZTBg3Oowg3UoA4EODzDK7w5D86L8+58zFpzTjazD3/gfP4AfoyO8Q==</latexit><latexit sha1_base64="bJO/yx8i5AStgfi/Tem5b15rC+s=">AAAB73icbVBNSwMxEJ2tX7V+VT16CRaheii7IuhFKHrxWMF+QLuWbJptQ5PsmmTFsvRPePGgiFf/jjf/jWm7B219MPB4b4aZeUHMmTau++3klpZXVtfy64WNza3tneLuXkNHiSK0TiIeqVaANeVM0rphhtNWrCgWAafNYHg98ZuPVGkWyTsziqkvcF+ykBFsrNQa3J+Un44vvW6x5FbcKdAi8TJSggy1bvGr04tIIqg0hGOt254bGz/FyjDC6bjQSTSNMRniPm1bKrGg2k+n947RkVV6KIyULWnQVP09kWKh9UgEtlNgM9Dz3kT8z2snJrzwUybjxFBJZovChCMTocnzqMcUJYaPLMFEMXsrIgOsMDE2ooINwZt/eZE0TiueW/Fuz0rVqyyOPBzAIZTBg3Oowg3UoA4EODzDK7w5D86L8+58zFpzTjazD3/gfP4AfoyO8Q==</latexit><latexit sha1_base64="bJO/yx8i5AStgfi/Tem5b15rC+s=">AAAB73icbVBNSwMxEJ2tX7V+VT16CRaheii7IuhFKHrxWMF+QLuWbJptQ5PsmmTFsvRPePGgiFf/jjf/jWm7B219MPB4b4aZeUHMmTau++3klpZXVtfy64WNza3tneLuXkNHiSK0TiIeqVaANeVM0rphhtNWrCgWAafNYHg98ZuPVGkWyTsziqkvcF+ykBFsrNQa3J+Un44vvW6x5FbcKdAi8TJSggy1bvGr04tIIqg0hGOt254bGz/FyjDC6bjQSTSNMRniPm1bKrGg2k+n947RkVV6KIyULWnQVP09kWKh9UgEtlNgM9Dz3kT8z2snJrzwUybjxFBJZovChCMTocnzqMcUJYaPLMFEMXsrIgOsMDE2ooINwZt/eZE0TiueW/Fuz0rVqyyOPBzAIZTBg3Oowg3UoA4EODzDK7w5D86L8+58zFpzTjazD3/gfP4AfoyO8Q==</latexit><latexit sha1_base64="bJO/yx8i5AStgfi/Tem5b15rC+s=">AAAB73icbVBNSwMxEJ2tX7V+VT16CRaheii7IuhFKHrxWMF+QLuWbJptQ5PsmmTFsvRPePGgiFf/jjf/jWm7B219MPB4b4aZeUHMmTau++3klpZXVtfy64WNza3tneLuXkNHiSK0TiIeqVaANeVM0rphhtNWrCgWAafNYHg98ZuPVGkWyTsziqkvcF+ykBFsrNQa3J+Un44vvW6x5FbcKdAi8TJSggy1bvGr04tIIqg0hGOt254bGz/FyjDC6bjQSTSNMRniPm1bKrGg2k+n947RkVV6KIyULWnQVP09kWKh9UgEtlNgM9Dz3kT8z2snJrzwUybjxFBJZovChCMTocnzqMcUJYaPLMFEMXsrIgOsMDE2ooINwZt/eZE0TiueW/Fuz0rVqyyOPBzAIZTBg3Oowg3UoA4EODzDK7w5D86L8+58zFpzTjazD3/gfP4AfoyO8Q==</latexit>

h⇤(x) = 0<latexit sha1_base64="b8wIbc/+tukWGvdoBJNhlSOi15I=">AAAB73icbVBNSwMxEJ2tX7V+VT16CRaheii7IuhFKHrxWMF+QLuWbJptQ5PsmmTFsvRPePGgiFf/jjf/jWm7B219MPB4b4aZeUHMmTau++3klpZXVtfy64WNza3tneLuXkNHiSK0TiIeqVaANeVM0rphhtNWrCgWAafNYHg98ZuPVGkWyTsziqkvcF+ykBFsrNQa3J+Un44v3W6x5FbcKdAi8TJSggy1bvGr04tIIqg0hGOt254bGz/FyjDC6bjQSTSNMRniPm1bKrGg2k+n947RkVV6KIyULWnQVP09kWKh9UgEtlNgM9Dz3kT8z2snJrzwUybjxFBJZovChCMTocnzqMcUJYaPLMFEMXsrIgOsMDE2ooINwZt/eZE0TiueW/Fuz0rVqyyOPBzAIZTBg3Oowg3UoA4EODzDK7w5D86L8+58zFpzTjazD3/gfP4AfQiO8A==</latexit><latexit sha1_base64="b8wIbc/+tukWGvdoBJNhlSOi15I=">AAAB73icbVBNSwMxEJ2tX7V+VT16CRaheii7IuhFKHrxWMF+QLuWbJptQ5PsmmTFsvRPePGgiFf/jjf/jWm7B219MPB4b4aZeUHMmTau++3klpZXVtfy64WNza3tneLuXkNHiSK0TiIeqVaANeVM0rphhtNWrCgWAafNYHg98ZuPVGkWyTsziqkvcF+ykBFsrNQa3J+Un44v3W6x5FbcKdAi8TJSggy1bvGr04tIIqg0hGOt254bGz/FyjDC6bjQSTSNMRniPm1bKrGg2k+n947RkVV6KIyULWnQVP09kWKh9UgEtlNgM9Dz3kT8z2snJrzwUybjxFBJZovChCMTocnzqMcUJYaPLMFEMXsrIgOsMDE2ooINwZt/eZE0TiueW/Fuz0rVqyyOPBzAIZTBg3Oowg3UoA4EODzDK7w5D86L8+58zFpzTjazD3/gfP4AfQiO8A==</latexit><latexit sha1_base64="b8wIbc/+tukWGvdoBJNhlSOi15I=">AAAB73icbVBNSwMxEJ2tX7V+VT16CRaheii7IuhFKHrxWMF+QLuWbJptQ5PsmmTFsvRPePGgiFf/jjf/jWm7B219MPB4b4aZeUHMmTau++3klpZXVtfy64WNza3tneLuXkNHiSK0TiIeqVaANeVM0rphhtNWrCgWAafNYHg98ZuPVGkWyTsziqkvcF+ykBFsrNQa3J+Un44v3W6x5FbcKdAi8TJSggy1bvGr04tIIqg0hGOt254bGz/FyjDC6bjQSTSNMRniPm1bKrGg2k+n947RkVV6KIyULWnQVP09kWKh9UgEtlNgM9Dz3kT8z2snJrzwUybjxFBJZovChCMTocnzqMcUJYaPLMFEMXsrIgOsMDE2ooINwZt/eZE0TiueW/Fuz0rVqyyOPBzAIZTBg3Oowg3UoA4EODzDK7w5D86L8+58zFpzTjazD3/gfP4AfQiO8A==</latexit><latexit sha1_base64="b8wIbc/+tukWGvdoBJNhlSOi15I=">AAAB73icbVBNSwMxEJ2tX7V+VT16CRaheii7IuhFKHrxWMF+QLuWbJptQ5PsmmTFsvRPePGgiFf/jjf/jWm7B219MPB4b4aZeUHMmTau++3klpZXVtfy64WNza3tneLuXkNHiSK0TiIeqVaANeVM0rphhtNWrCgWAafNYHg98ZuPVGkWyTsziqkvcF+ykBFsrNQa3J+Un44v3W6x5FbcKdAi8TJSggy1bvGr04tIIqg0hGOt254bGz/FyjDC6bjQSTSNMRniPm1bKrGg2k+n947RkVV6KIyULWnQVP09kWKh9UgEtlNgM9Dz3kT8z2snJrzwUybjxFBJZovChCMTocnzqMcUJYaPLMFEMXsrIgOsMDE2ooINwZt/eZE0TiueW/Fuz0rVqyyOPBzAIZTBg3Oowg3UoA4EODzDK7w5D86L8+58zFpzTjazD3/gfP4AfQiO8A==</latexit>

Threshold classifier h(x) = 1 i↵ x � ✓h where ✓h 2 {1, 2, . . . , n}<latexit sha1_base64="okjrBwn3TQs74w5Bw4xsxwItmNE=">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</latexit><latexit sha1_base64="okjrBwn3TQs74w5Bw4xsxwItmNE=">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</latexit><latexit sha1_base64="okjrBwn3TQs74w5Bw4xsxwItmNE=">AAACPnicbVBNS8NAFNz4bf2qevSy2AgKpSS96EUQvXhUsCo0pWy2L83iZhN3X9QS+su8+Bu8efTiQRGvHt3WCn4NLAwzb9j3JsykMOh5D87Y+MTk1PTMbGlufmFxqby8cmrSXHNo8FSm+jxkBqRQ0ECBEs4zDSwJJZyFFwcD/+wKtBGpOsFeBq2EdZWIBGdopXa5cRJrMHEqO5RLZoy1QFM33rzZ2vVdKqKIujdBFy5pgDEga8cuvY5BA3W/hECooPCr9WrQSdFUVdB32+WKV/OGoH+JPyIVMsJRu3xvwzxPQOFwjabvZdgqmEbBJfRLQW4gY/yCdaFpqWIJmFYxPL9PN6zSoVGq7VNIh+r3RMESY3pJaCcThrH57Q3E/7xmjtFOqxAqyxEU//woyiXFlA66pB2hgaPsWcK4FnZXymOmGUfbeMmW4P8++S85rdd8r+Yf1yt7+6M6ZsgaWSebxCfbZI8ckiPSIJzckkfyTF6cO+fJeXXePkfHnFFmlfyA8/4BJZmtRQ==</latexit><latexit sha1_base64="okjrBwn3TQs74w5Bw4xsxwItmNE=">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</latexit>

Complexity of passive learning: Opnq; active learning: Oplogpnqq; teaching: 2.

Interaction Protocol

1: learner’s initial version space is H0 “ H and learner starts from h0 P H2: for t “ 1, 2, 3, . . . do3: teacher provides zt “ pxt, h

‹pxtqq4: learner updates Ht “ Ht´1 XHptztuq; picks ht P Ht

5: teacher receives ht as feedback from the learner6: if ht “ h‹ then teaching process terminates

h⇤<latexit sha1_base64="YlEbT4YqbLx3S6ZM2rvB8UgtthM=">AAAB6nicdZDLSgMxFIbP1Futt6pLN8EiiIuSKa1twUXBjcuK9gLtWDJppg3NXEgyQhn6CG5cKOLWJ3Ln25hpK6joD4GP/5xDzvndSHClMf6wMiura+sb2c3c1vbO7l5+/6CtwlhS1qKhCGXXJYoJHrCW5lqwbiQZ8V3BOu7kMq137plUPAxu9TRijk9GAfc4JdpYN+O7s0G+gIulCq5XawgXK9iul0sGMK7VzzGyDaQqwFLNQf69Pwxp7LNAU0GU6tk40k5CpOZUsFmuHysWETohI9YzGBCfKSeZrzpDJ8YZIi+U5gUazd3vEwnxlZr6run0iR6r37XU/KvWi7VXcxIeRLFmAV185MUC6RCld6Mhl4xqMTVAqORmV0THRBKqTTo5E8LXpeh/aJeKtuHrcqFxsYwjC0dwDKdgQxUacAVNaAGFETzAEzxbwnq0XqzXRWvGWs4cwg9Zb59SFI3N</latexit><latexit sha1_base64="YlEbT4YqbLx3S6ZM2rvB8UgtthM=">AAAB6nicdZDLSgMxFIbP1Futt6pLN8EiiIuSKa1twUXBjcuK9gLtWDJppg3NXEgyQhn6CG5cKOLWJ3Ln25hpK6joD4GP/5xDzvndSHClMf6wMiura+sb2c3c1vbO7l5+/6CtwlhS1qKhCGXXJYoJHrCW5lqwbiQZ8V3BOu7kMq137plUPAxu9TRijk9GAfc4JdpYN+O7s0G+gIulCq5XawgXK9iul0sGMK7VzzGyDaQqwFLNQf69Pwxp7LNAU0GU6tk40k5CpOZUsFmuHysWETohI9YzGBCfKSeZrzpDJ8YZIi+U5gUazd3vEwnxlZr6run0iR6r37XU/KvWi7VXcxIeRLFmAV185MUC6RCld6Mhl4xqMTVAqORmV0THRBKqTTo5E8LXpeh/aJeKtuHrcqFxsYwjC0dwDKdgQxUacAVNaAGFETzAEzxbwnq0XqzXRWvGWs4cwg9Zb59SFI3N</latexit><latexit sha1_base64="YlEbT4YqbLx3S6ZM2rvB8UgtthM=">AAAB6nicdZDLSgMxFIbP1Futt6pLN8EiiIuSKa1twUXBjcuK9gLtWDJppg3NXEgyQhn6CG5cKOLWJ3Ln25hpK6joD4GP/5xDzvndSHClMf6wMiura+sb2c3c1vbO7l5+/6CtwlhS1qKhCGXXJYoJHrCW5lqwbiQZ8V3BOu7kMq137plUPAxu9TRijk9GAfc4JdpYN+O7s0G+gIulCq5XawgXK9iul0sGMK7VzzGyDaQqwFLNQf69Pwxp7LNAU0GU6tk40k5CpOZUsFmuHysWETohI9YzGBCfKSeZrzpDJ8YZIi+U5gUazd3vEwnxlZr6run0iR6r37XU/KvWi7VXcxIeRLFmAV185MUC6RCld6Mhl4xqMTVAqORmV0THRBKqTTo5E8LXpeh/aJeKtuHrcqFxsYwjC0dwDKdgQxUacAVNaAGFETzAEzxbwnq0XqzXRWvGWs4cwg9Zb59SFI3N</latexit><latexit sha1_base64="YlEbT4YqbLx3S6ZM2rvB8UgtthM=">AAAB6nicdZDLSgMxFIbP1Futt6pLN8EiiIuSKa1twUXBjcuK9gLtWDJppg3NXEgyQhn6CG5cKOLWJ3Ln25hpK6joD4GP/5xDzvndSHClMf6wMiura+sb2c3c1vbO7l5+/6CtwlhS1qKhCGXXJYoJHrCW5lqwbiQZ8V3BOu7kMq137plUPAxu9TRijk9GAfc4JdpYN+O7s0G+gIulCq5XawgXK9iul0sGMK7VzzGyDaQqwFLNQf69Pwxp7LNAU0GU6tk40k5CpOZUsFmuHysWETohI9YzGBCfKSeZrzpDJ8YZIi+U5gUazd3vEwnxlZr6run0iR6r37XU/KvWi7VXcxIeRLFmAV185MUC6RCld6Mhl4xqMTVAqORmV0THRBKqTTo5E8LXpeh/aJeKtuHrcqFxsYwjC0dwDKdgQxUacAVNaAGFETzAEzxbwnq0XqzXRWvGWs4cwg9Zb59SFI3N</latexit>

ht<latexit sha1_base64="b4pog08irk6aL8XZeB5TlxVyTdc=">AAAB6nicbZBNS8NAEIYn9avWr6pHL4tF8FQSEfTgoeDFY0X7AW0om+2mXbrZhN2JUEJ/ghcPinj1F3nz37hNc9DWFxYe3plhZ94gkcKg6347pbX1jc2t8nZlZ3dv/6B6eNQ2caoZb7FYxrobUMOlULyFAiXvJprTKJC8E0xu5/XOE9dGxOoRpwn3IzpSIhSMorUexgMcVGtu3c1FVsEroAaFmoPqV38YszTiCpmkxvQ8N0E/oxoFk3xW6aeGJ5RN6Ij3LCoaceNn+aozcmadIQljbZ9Ckru/JzIaGTONAtsZURyb5drc/K/WSzG89jOhkhS5YouPwlQSjMn8bjIUmjOUUwuUaWF3JWxMNWVo06nYELzlk1ehfVH3LN9f1ho3RRxlOIFTOAcPrqABd9CEFjAYwTO8wpsjnRfn3flYtJacYuYY/sj5/AFXEI3N</latexit><latexit sha1_base64="b4pog08irk6aL8XZeB5TlxVyTdc=">AAAB6nicbZBNS8NAEIYn9avWr6pHL4tF8FQSEfTgoeDFY0X7AW0om+2mXbrZhN2JUEJ/ghcPinj1F3nz37hNc9DWFxYe3plhZ94gkcKg6347pbX1jc2t8nZlZ3dv/6B6eNQ2caoZb7FYxrobUMOlULyFAiXvJprTKJC8E0xu5/XOE9dGxOoRpwn3IzpSIhSMorUexgMcVGtu3c1FVsEroAaFmoPqV38YszTiCpmkxvQ8N0E/oxoFk3xW6aeGJ5RN6Ij3LCoaceNn+aozcmadIQljbZ9Ckru/JzIaGTONAtsZURyb5drc/K/WSzG89jOhkhS5YouPwlQSjMn8bjIUmjOUUwuUaWF3JWxMNWVo06nYELzlk1ehfVH3LN9f1ho3RRxlOIFTOAcPrqABd9CEFjAYwTO8wpsjnRfn3flYtJacYuYY/sj5/AFXEI3N</latexit><latexit sha1_base64="b4pog08irk6aL8XZeB5TlxVyTdc=">AAAB6nicbZBNS8NAEIYn9avWr6pHL4tF8FQSEfTgoeDFY0X7AW0om+2mXbrZhN2JUEJ/ghcPinj1F3nz37hNc9DWFxYe3plhZ94gkcKg6347pbX1jc2t8nZlZ3dv/6B6eNQ2caoZb7FYxrobUMOlULyFAiXvJprTKJC8E0xu5/XOE9dGxOoRpwn3IzpSIhSMorUexgMcVGtu3c1FVsEroAaFmoPqV38YszTiCpmkxvQ8N0E/oxoFk3xW6aeGJ5RN6Ij3LCoaceNn+aozcmadIQljbZ9Ckru/JzIaGTONAtsZURyb5drc/K/WSzG89jOhkhS5YouPwlQSjMn8bjIUmjOUUwuUaWF3JWxMNWVo06nYELzlk1ehfVH3LN9f1ho3RRxlOIFTOAcPrqABd9CEFjAYwTO8wpsjnRfn3flYtJacYuYY/sj5/AFXEI3N</latexit><latexit sha1_base64="b4pog08irk6aL8XZeB5TlxVyTdc=">AAAB6nicbZBNS8NAEIYn9avWr6pHL4tF8FQSEfTgoeDFY0X7AW0om+2mXbrZhN2JUEJ/ghcPinj1F3nz37hNc9DWFxYe3plhZ94gkcKg6347pbX1jc2t8nZlZ3dv/6B6eNQ2caoZb7FYxrobUMOlULyFAiXvJprTKJC8E0xu5/XOE9dGxOoRpwn3IzpSIhSMorUexgMcVGtu3c1FVsEroAaFmoPqV38YszTiCpmkxvQ8N0E/oxoFk3xW6aeGJ5RN6Ij3LCoaceNn+aozcmadIQljbZ9Ckru/JzIaGTONAtsZURyb5drc/K/WSzG89jOhkhS5YouPwlQSjMn8bjIUmjOUUwuUaWF3JWxMNWVo06nYELzlk1ehfVH3LN9f1ho3RRxlOIFTOAcPrqABd9CEFjAYwTO8wpsjnRfn3flYtJacYuYY/sj5/AFXEI3N</latexit>

H({zt})<latexit sha1_base64="(null)">(null)</latexit><latexit sha1_base64="(null)">(null)</latexit><latexit sha1_base64="(null)">(null)</latexit><latexit sha1_base64="(null)">(null)</latexit>

Ht�1<latexit sha1_base64="(null)">(null)</latexit><latexit sha1_base64="(null)">(null)</latexit><latexit sha1_base64="(null)">(null)</latexit><latexit sha1_base64="(null)">(null)</latexit>

Ht<latexit sha1_base64="(null)">(null)</latexit><latexit sha1_base64="(null)">(null)</latexit><latexit sha1_base64="(null)">(null)</latexit><latexit sha1_base64="(null)">(null)</latexit>

ht�1<latexit sha1_base64="(null)">(null)</latexit><latexit sha1_base64="(null)">(null)</latexit><latexit sha1_base64="(null)">(null)</latexit><latexit sha1_base64="(null)">(null)</latexit>

h⇤<latexit sha1_base64="(null)">(null)</latexit><latexit sha1_base64="(null)">(null)</latexit><latexit sha1_base64="(null)">(null)</latexit><latexit sha1_base64="(null)">(null)</latexit>

Complexity Measures

Notions DescriptionTD classical worst-case teaching complexityRTD notion of TD when teaching a collaborative learnerNCTD strongest notion of TD that respects collusion-freeness

Local-PBTD teaching complexity of a weak sequential model

Research Questions

• Is there a framework unifying different notions of TD’s?

• Can we identify models with teaching complexity linear inthe Vapnik–Chervonenkis dimension VCD?

Our Contributions

A novel framework capturing the teaching process via preference functions Σ, where each functionσ P Σ induces a teacher-learner pair. Our main results are as follows:

• We show that existing batch models correspond to spe-cific families of σ functions in our framework.

• We identify sequential models with teaching complexitylinear in the VCD of the hypothesis class.

• We provide a constructive procedure to find σ functionswith low teaching complexity.

Σconst

ΣglobalΣgvsΣlocal

Σlvs

Table 1: Main Resuls

Families Σconst Σglobal Σgvs Σlocal Σlvs

Reduction TD RTD NCTD Local-PBTD –

Complexity Results – OpVCD2q OpVCD2

q OpVCD2q OpVCDq

[GK95] [Zil+11] [KSZ19] [Che+18] –

Learner’s Preference Function

A preference function σ : Hˆ 2H ˆHÑ R models how a learner navigates in the version space as itreceives teaching examples (line 4 of Interaction Protocol):

ht P arg minh1PHt

σph1;Ht, ht´1q.

Teaching Complexity Σ-TD

Teaching Dimension for a Preference Function

Fix X , H, and learner’s initial hypothesis h0. Let DX ,H,h0pσ, h‹q be the worst-case optimal cost for

steering the learner from h0 to h‹ for some preference function σ. Then, the teaching dimension w.r.t.σ is defined as the worst-case optimal cost for teaching any target h‹:

TDX ,H,h0pσq “ maxh‹

DX ,H,h0pσ, h‹q.

Teaching Dimension for a Family of Preference Functions

We define the teaching dimension for a family Σ as the teaching dimension w.r.t. the best σ P Σ:

Σ-TDX ,H,h0 “ minσPΣ

TDX ,H,h0pσq.

Collusion-free Preference Functions

Definition 1 (Collusion-free teaching [GM96] (batch setting)) A learner outputtinghypothesis h will not change its output if given additional information consistent with h.

Definition 2 (Collusion-free preference (this paper)) If h is the only hypothesis in themost preferred set defined by σ, then the learner will stay at h if additional information receivedby the learner is consistent with h.

We study preference functions that are collusion-free as per Definition 2:

ΣCF “ tσ | σ is collusion-freeu.

Preference-based Teaching Models

• Batch models:

- Σconst “ tσ P ΣCF | Dc P R, s.t. @h1, H, h, σph1;H, hq “ cu

- Σglobal “ tσ P ΣCF | D g : HÑ R, s.t. @h1, H, h, σph1;H, hq “ gph1qu

- Σgvs “ tσ P ΣCF | D g : H ˆ 2H Ñ R, s.t. @h1, H, h, σph1;H, hq “ gph1, Hqu

• Sequential models:

- Σlocal “ tσ P ΣCF | D g : H ˆHÑ R, s.t. @h1, H, h, σph1;H, hq “ gph1, hqu

- Σlvs “ tσ P ΣCF | D g : H ˆ 2H ˆHÑ R, s.t. @h1, H, h, σph1;H, hq “ gph1, H, hqu

• Teaching sequences with different preference functions for the Warmuth hypothesis class:

HHHHHhx

x1 x2 x3 x4 x5 Sconst “ Sglobal Sgvs Slocal Slvs

h1 1 1 0 0 0 px1, x2, x4q px1, x2q px1q px1qh2 0 1 1 0 0 px2, x3, x5q px2, x3q px3q px2qh3 0 0 1 1 0 px1, x3, x4q px3, x4q px3, x4q px3qh4 0 0 0 1 1 px2, x4, x5q px4, x5q px5, x4q px4qh5 1 0 0 0 1 px1, x3, x5q px1, x5q px5q px5qh6 1 1 0 1 0 px1, x2, x4q px2, x4q px4q px3qh7 0 1 1 0 1 px2, x3, x5q px3, x5q px3, x5q px4qh8 1 0 1 1 0 px1, x3, x4q px1, x4q px4, x3q px5qh9 0 1 0 1 1 px2, x4, x5q px2, x5q px4, x5q px1qh10 1 0 1 0 1 px1, x3, x5q px1, x3q px5, x3q px2q

(a) The Warmuth hypothesis class and the corresponding teaching sequences (denoted by S).

h1 @h1 P H�constph1; ¨, ¨q 0�globalph1; ¨, ¨q

(b) �const and �global

hzh1 h1 h2 h3 h4 h5 h6 h7 h8 h9 h10

�localph1; ¨, h “ h1q 0 2 4 4 2 1 3 3 3 3. . .

(c) �local representing the Hamming distance between h1 and h.

h1 h1 h2 . . .

Hth1, h6u th2, h7u . . .

th1u th2u . . .�gvs 0 0 . . .

(d) �gvsph1; H, ¨q

h1 h1 h2 . . .

Hth1uY th2uY . . .

th5, h6, h8, h10u˚ th1, h7, h6, h9u˚ . . .h h1 h1 h2 . . .�lvs 0 0 0 . . .

(e) �lvsph1; H, hq. Here, t¨u˚ denotes all subsets.

Table 2: Teaching sequences with different preference functions for the Warmuth hypothesis class[DFSZ14].4 Full preference functions are given in Appendix B.

The second family, denoted by ⌃lvs, corresponds to the preference functions that depend on all threearguments of �ph1; H, hq. The dependence of � on the learner’s current (local) hypothesis and theversion space renders a powerful family of preference functions:

⌃lvs “ t� P ⌃CF | D g : H ˆ 2H ˆ H Ñ R, s.t. @h1, H, h,�ph1; H, hq “ gph1, H, hqu

Figure 1 illustrates the relationship between these preference families. As an example, in Table 2cand Table 2e, we provide the preference functions �local and �lvs for the Warmuth hypothesis classthat achieve the minima in Eq. (3.2).

5.2 Comparing ⌃gvs-TD and ⌃local-TD

In the following, we show that substantial differences arise as we transition from � functions inducingthe strongest batch (i.e., non-clashing) model to � functions inducing a weak sequential (i.e., localpreference-based) model. We provide the full proof of Theorem 2 in Appendix C.

Theorem 2 Neither of the families ⌃gvs and ⌃local dominates the other. Specifically,

1. ⌃gvs X ⌃local “ ⌃global

2. There exist H, X , where @h0 P H,⌃local-TDX ,H,h0° ⌃gvs-TDX ,H,h0

3. There exist H, X , where @h0 P H,⌃local-TDX ,H,h0 † ⌃gvs-TDX ,H,h0

5.3 Complexity Results

We now connect the teaching complexity of the sequential models with the VC dimension.

Theorem 3 ⌃local-TDX ,H,h0“ OpVCDpH, X q2q, and ⌃lvs-TDX ,H,h0

“ OpVCDpH, X qq.

To establish the proof, we first introduce an important definition (Definition 6) and a key lemma(Lemma 4).

4The Warmuth hypothesis class is the smallest concept class for which RTD exceeds VCD.

6

Main Results

• Reduction to existing notions of TD’s (see Table 1).

• Proving Σlvs-TDX ,H,h0 “ O`

VCDpH,X q˘

via a constructive procedure.

Key Ideas for Constructing σ P Σlvs with TDX ,H,h0pσq “ OpVCDq

• Introducing a new notion of compact distinguishable set.

• Partitioning the hypothesis class into subsets of hypothesis classes with lower VCD using the compact distinguishable set.

• Recursively applying the partitioning procedure to create the preference function σ.

Discussions

• Designing σ functions for addressing the open question of whether RTD is linear in VCD.

• Designing teaching algorithms for sequential models.

References

[GK95] Sally A Goldman and Michael J Kearns. “On the complexity of teaching”. In: J. Comput. Syst. Sci 50.1 (1995), pp. 20–31.

[Zil+11] Sandra Zilles, Steffen Lange, Robert Holte, and Martin Zinkevich. “Models of cooperative teaching and learning”. In: JMLR 12.Feb(2011), pp. 349–384.

[KSZ19] David Kirkpatrick, Hans U. Simon, and Sandra Zilles. “Optimal Collusion-Free Teaching”. In: ALT. Vol. 98. 2019, pp. 506–528.

[Che+18] Yuxin Chen, Adish Singla, Oisin Mac Aodha, Pietro Perona, and Yisong Yue. “Understanding the role of adaptivity in machineteaching: The case of version space learners”. In: NeurIPS. 2018, pp. 1476–1486.

[GM96] Sally A Goldman and H David Mathias. “Teaching a smarter learner”. In: J. Comput. Syst. Sci 52.2 (1996), pp. 255–267.