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Red Points and Blue Points (SIMONS-TCS-ML)

Professor

38:15·2026·research level

Santosh Vempala presents a simple algorithm for separating red and blue points in n-dimensional space, improving complexity for separation by an intersection of k halfspaces under a soft margin.

Santosh Vempala (Georgia Institute of Technology)

The Role of TCS in Modern Machine Learning

Given points in n-dimensional space drawn independently from an arbitrary (unknown) distribution and labeled red or blue so that the colors can be separated by an (unknown) intersection of k halfspaces, can you efficiently compute (learn) a rule to separate the colors? Avrim posed this question in my first meeting with him 33 years ago, and I've been (happily) struggling with it since. In this talk, I'll describe a simple algorithm with complexity exponential in \sqrt{n \log(1/\rho) \log k}), assuming a (soft) margin \rho. This improves known results (which are exponential in either k or 1/\rho) and matches statistical query and cryptographic lower bounds up to the logarithmic factors in k and 1/rho.

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