Speeding up Training with Tree Kernels for Node Relation Labeling

We present a method for speeding up the calculation of tree kernels during training. The calculation of tree kernels is still heavy even with efficient dynamic programming (DP) procedures. Our method maps trees into a small feature space where the inner product, which can be calculated much faster, yields the same value as the tree kernel for most tree pairs. The training is sped up by using the DP procedure only for the exceptional pairs. We describe an algorithm that detects such exceptional pairs and converts trees into vectors in a feature space. We propose tree kernels on marked labeled ordered trees and show that the training of SVMs for semantic role labeling using these kernels can be sped up by a factor of several tens.