Part of Advances in Neural Information Processing Systems 28 (NIPS 2015)
Rémi Bardenet, Michalis Titsias RC AUEB
Determinantal point processes (DPPs) are point process models thatnaturally encode diversity between the points of agiven realization, through a positive definite kernel $K$. DPPs possess desirable properties, such as exactsampling or analyticity of the moments, but learning the parameters ofkernel $K$ through likelihood-based inference is notstraightforward. First, the kernel that appears in thelikelihood is not $K$, but another kernel $L$ related to $K$ throughan often intractable spectral decomposition. This issue is typically bypassed in machine learning bydirectly parametrizing the kernel $L$, at the price of someinterpretability of the model parameters. We follow this approachhere. Second, the likelihood has an intractable normalizingconstant, which takes the form of large determinant in the case of aDPP over a finite set of objects, and the form of a Fredholm determinant in thecase of a DPP over a continuous domain. Our main contribution is to derive bounds on the likelihood ofa DPP, both for finite and continuous domains. Unlike previous work, our bounds arecheap to evaluate since they do not rely on approximating the spectrumof a large matrix or an operator. Through usual arguments, these bounds thus yield cheap variationalinference and moderately expensive exact Markov chain Monte Carlo inference methods for DPPs.