MLE-induced Likelihood for Markov Random Fields
This addresses a fundamental bottleneck in statistical inference for MRFs, offering a scalable solution for researchers and practitioners, though it appears incremental as it builds on existing approximation concepts.
The paper tackles the intractable likelihood problem in Markov random fields by proposing a novel approximation method that reconstructs the joint likelihood from marginal likelihoods using a copula, showing superior performance with consistent numerical results and computational cost as MRF size increases, unlike existing methods that deteriorate or become unbearable.
Due to the intractable partition function, the exact likelihood function for a Markov random field (MRF), in many situations, can only be approximated. Major approximation approaches include pseudolikelihood and Laplace approximation. In this paper, we propose a novel way of approximating the likelihood function through first approximating the marginal likelihood functions of individual parameters and then reconstructing the joint likelihood function from these marginal likelihood functions. For approximating the marginal likelihood functions, we derive a particular likelihood function from a modified scenario of coin tossing which is useful for capturing how one parameter interacts with the remaining parameters in the likelihood function. For reconstructing the joint likelihood function, we use an appropriate copula to link up these marginal likelihood functions. Numerical investigation suggests the superior performance of our approach. Especially as the size of the MRF increases, both the numerical performance and the computational cost of our approach remain consistently satisfactory, whereas Laplace approximation deteriorates and pseudolikelihood becomes computationally unbearable.