Particle Gibbs for Bayesian Additive Regression Trees

Additive regression trees are flexible non-parametric models and popular off-the-shelf tools for real-world non-linear regression. In application domains, such as bioinformatics, where there is also demand for probabilistic predictions with measures of uncertainty, the Bayesian additive regression trees (BART) model, introduced by Chipman et al. (2010), is increasingly popular. As data sets have grown in size, however, the standard Metropolis-Hastings algorithms used to perform inference in BART are proving inadequate. In particular, these Markov chains make local changes to the trees and suffer from slow mixing when the data are high-dimensional or the best fitting trees are more than a few layers deep. We present a novel sampler for BART based on the Particle Gibbs (PG) algorithm (Andrieu et al., 2010) and a top-down particle filtering algorithm for Bayesian decision trees (Lakshminarayanan et al., 2013). Rather than making local changes to individual trees, the PG sampler proposes a complete tree to fit the residual. Experiments show that the PG sampler outperforms existing samplers in many settings

Training Big Random Forests with Little Resources

Without access to large compute clusters, building random forests on large datasets is still a challenging problem. This is, in particular, the case if fully-grown trees are desired. We propose a simple yet effective framework that allows to efficiently construct ensembles of huge trees for hundreds of millions or even billions of training instances using a cheap desktop computer with commodity hardware. The basic idea is to consider a multi-level construction scheme, which builds top trees for small random subsets of the available data and which subsequently distributes all training instances to the top trees' leaves for further processing. While being conceptually simple, the overall efficiency crucially depends on the particular implementation of the different phases. The practical merits of our approach are demonstrated using dense datasets with hundreds of millions of training instances.Comment: 9 pages, 9 Figure

Effect of Integrated nutrient management (INM) on growth attributes, biomass yield, secondary nutrient uptake and quality parameters of bhendi (Abelmoschus esculentus L.)

Organic manure from different sources could be an effective substitute of chemical fertilizers. Therefore, a field experiment was conducted to study the impact of various sources of organic manures viz., sole application of composted pressmud, vermicompost, sewage sludge and farmyard manure and its combination with various levels of inorganic fertilizers on growth attributes, biomass yield, yield attributes, secondary nutrient uptake and its available status and quality parameters of bhendi (A. esculentus (L.) Moench). The results indicated that application of pressmud @ 5 t ha-1 with 50 per cent recommended dose of fertilizer had recorded the highest calcium and magnesium uptake of 30.9 and 15.4 kg ha-1 respectively and biomass yield of 2233.2 kg ha-1, In comparison to control, the increases in biomass yield and calcium and magnesium uptake were 20 and 51 and 136% higher under the same set of treatment combinations . The results revealed that treatment received with pressmud application @ 5 t ha-1 along with 50 per cent recommended dose of fertilizers registered highest available calcium and magnesium content of 0.14 and 0.28% respectively. In addition to that, there was an improvement in growth parameters such as plant height and number of branches plant-1 at all the growth stages of crop and also quality attributes viz., crude fibre (10.2%) and mucilage content (1.56%) were recorded significantly highest by same treatment compared to control (15.0 and 1.2% respectively). Among the organics, pressmud based inorganic fertilizers application was suitable for higher biomass yield, improvement in quality parameters and also maintaining the fertility status of the secondary nutrients in soil

Radiative stability of neutrino-mass textures

Neutrino-mass textures proposed at high-scales are known to be unstable against radiative corrections especially for nearly degenerate eigen values. Within the renormalization group constraints we find a mechanism in a class of gauge theories which guarantees reproduction of any high-scale texture at low energies with radiative stability. We also show how the mechanism explains solar and atmospheric neutrino anomalies through the bimaximal texture at high scale.Comment: 4 pages REVTEX, 1 Postscript fi

Identification and description of Indian parasitic bee genus Sphecodes Latreille 1804, (Halictidae: Hymenoptera)

The present study provides an updated knowledge on taxonomy of three important species of Sphecodes Latreille, 1804 which were collected from different parts of India. Three species viz., Sphecodes iridipennis Smith 1879, S. gibbus Smith 1853, S. crassicornis Smith 1879 are redescribed with illustrations, genitalic features and measurements of their morphological features. An annotated checklist of species Sphecodes from India also provided