Born-Again Tree Ensembles

The use of machine learning algorithms in finance, medicine, and criminal justice can deeply impact human lives. As a consequence, research into interpretable machine learning has rapidly grown in an attempt to better control and fix possible sources of mistakes and biases. Tree ensembles offer a good prediction quality in various domains, but the concurrent use of multiple trees reduces the interpretability of the ensemble. Against this background, we study born-again tree ensembles, i.e., the process of constructing a single decision tree of minimum size that reproduces the exact same behavior as a given tree ensemble in its entire feature space. To find such a tree, we develop a dynamic-programming based algorithm that exploits sophisticated pruning and bounding rules to reduce the number of recursive calls. This algorithm generates optimal born-again trees for many datasets of practical interest, leading to classifiers which are typically simpler and more interpretable without any other form of compromise.Comment: "Born-Again Tree Ensembles", proceedings of ICML 2020. The associated source code is available at: https://github.com/vidalt/BA-Tree

On the freezing of variables in random constraint satisfaction problems

The set of solutions of random constraint satisfaction problems (zero energy groundstates of mean-field diluted spin glasses) undergoes several structural phase transitions as the amount of constraints is increased. This set first breaks down into a large number of well separated clusters. At the freezing transition, which is in general distinct from the clustering one, some variables (spins) take the same value in all solutions of a given cluster. In this paper we study the critical behavior around the freezing transition, which appears in the unfrozen phase as the divergence of the sizes of the rearrangements induced in response to the modification of a variable. The formalism is developed on generic constraint satisfaction problems and applied in particular to the random satisfiability of boolean formulas and to the coloring of random graphs. The computation is first performed in random tree ensembles, for which we underline a connection with percolation models and with the reconstruction problem of information theory. The validity of these results for the original random ensembles is then discussed in the framework of the cavity method.Comment: 32 pages, 7 figure

The folk fiddle music of Lithuania’s coastal regions

Publisher PD

Boston University Choral Ensembles, March 27, 2010

This is the concert program of the Boston University Choral Ensembles performance on Saturday, March 27, 2010 at 7:30 p.m., at Marsh Chapel, 735 Commonwealth Avenue, Boston, Massachusetts. Works performed were O Lux Beatissimia by Howard Helvey, Tomorrow Shall Be My Dancing Day arranged by John Rutter, Hark, I Hear the Harps Eternal by Alice Parker, Salmo 150 by Ernani Aguiar, Psalm 133 by Michael Hennagin, Blagoslovi, dushe moia, Gospoda by Pavel Chesnokov, Before I Go My Way by Peter Hamlin, The Ballad of Little Musgrave and Lady Barnard by Benjamin Britten, The Lighthearted Lovers by Kirke Mechem, "Ring Out, Wild Bells" from The Passing of the Year by Jonathan Dove, "Suite" de Lorca, Opus 72 by Einojuhani Rautavaara, Pilgrim's Hymn and The Rome Home by Stephen Paulus, Old America songs by Aaron Copland, Hold On! by Simpson, and I was glad when they said unto me by Charles Hubert and Hastings Parry. Digitization for Boston University Concert Programs was supported by the Boston University Center for the Humanities Library Endowed Fund

The heavy quark potential in QCD with 2 flavors of dynamical quarks

We compute the heavy quark potential on configurations generated by the HEMCGC collaboration with dynamical staggered fermions at $6/g^2 = 5.6$ and with dynamical Wilson fermions at $6/g^2 = 5.3$. The computations are done on $16^3 \times 32$ lattices, corresponding to physical sizes of about 1.6 and 2.3 fm, respectively. Up to the distances probed no sign of string breaking is detectable. We also compute the recently proposed scale $r_0$ defined by $r_0^2 F(r_0) = 1.65$.Comment: 8 pages with 3 figures. uuencoded postscript file. FSU-SCRI-94-0

Lattice QCD investigation of a doubly-bottom bˉbˉud\bar{b} \bar{b} u d tetraquark with quantum numbers I(JP)=0(1+)I(J^P) = 0(1^+)

We use lattice QCD to investigate the spectrum of the $\bar{b} \bar{b} u d$ four-quark system with quantum numbers $I(J^P) = 0(1^+)$. We use five different gauge-link ensembles with $2+1$ flavors of domain-wall fermions, including one at the physical pion mass, and treat the heavy $\bar{b}$ quark within the framework of lattice nonrelativistic QCD. Our work improves upon previous similar computations by considering in addition to local four-quark interpolators also nonlocal two-meson interpolators and by performing a L\"uscher analysis to extrapolate our results to infinite volume. We obtain a binding energy of $(-128 \pm 24 \pm 10) \, \textrm{MeV}$, corresponding to the mass $(10476 \pm 24 \pm 10) \, \textrm{MeV}$, which confirms the existence of a $\bar{b} \bar{b} u d$ tetraquark that is stable with respect to the strong and electromagnetic interactions.Comment: 27 pages, 13 figure