Tree Compression with Top Trees Revisited

We revisit tree compression with top trees (Bille et al, ICALP'13) and present several improvements to the compressor and its analysis. By significantly reducing the amount of information stored and guiding the compression step using a RePair-inspired heuristic, we obtain a fast compressor achieving good compression ratios, addressing an open problem posed by Bille et al. We show how, with relatively small overhead, the compressed file can be converted into an in-memory representation that supports basic navigation operations in worst-case logarithmic time without decompression. We also show a much improved worst-case bound on the size of the output of top-tree compression (answering an open question posed in a talk on this algorithm by Weimann in 2012).Comment: SEA 201

Deep Tree Transductions - A Short Survey

The paper surveys recent extensions of the Long-Short Term Memory networks to handle tree structures from the perspective of learning non-trivial forms of isomorph structured transductions. It provides a discussion of modern TreeLSTM models, showing the effect of the bias induced by the direction of tree processing. An empirical analysis is performed on real-world benchmarks, highlighting how there is no single model adequate to effectively approach all transduction problems.Comment: To appear in the Proceedings of the 2019 INNS Big Data and Deep Learning (INNSBDDL 2019). arXiv admin note: text overlap with arXiv:1809.0909

Mechanical properties of 10-year-old sentang (Azadirachta excelsa) grown from vegetative propagation

Mechanical properties of 10-year-old sentang (Azadirachta excelsa) grown from vegetative propagation. This paper reports the mechanical properties of sentang (Azadirachta excelsa) wood cut from trees that were planted by vegetative propagation, their variations along tree height and also between sapwood and heartwood. The correlation between selected anatomical properties as well as density and mechanical properties were also presented. There was no significant difference in modulus of rupture between wood from seedling and rooted- cutting trees. However, wood from rooted-cutting trees showed higher modulus of elasticity compared with wood from seedling trees. On the other hand, compression and shear parallel to the grain were significantly higher in wood planted from seedling compared with wood from rooted-cutting trees. There was an increase in mechanical properties at the bottom portion towards the top irrespective of the planting technique. Mechanical properties were higher in heartwood than in sapwood. Mechanical properties were correlated with anatomical properties rather than density. Rooted cutting could be a promising method for planting sentang, apart from seedling