Sample Compression for Real-Valued Learners

We give an algorithmically efficient version of the learner-to-compression scheme conversion in Moran and Yehudayoff (2016). We further extend this technique to real-valued hypotheses, to obtain a bounded-size sample compression scheme via an efficient reduction to a certain generic real-valued learning strategy. To our knowledge, this is the first general compressed regression result (regardless of efficiency or boundedness) guaranteeing uniform approximate reconstruction. Along the way, we develop a generic procedure for constructing weak real-valued learners out of abstract regressors; this result is also of independent interest. In particular, this result sheds new light on an open question of H. Simon (1997). We show applications to two regression problems: learning Lipschitz and bounded-variation functions.