Receipt from Etienne Delaunoy to C. Raffard [sic]

https://digitalcommons.salve.edu/goelet-interior/1070/thumbnail.jp

SAE: Sequential Anchored Ensembles

peer reviewedComputing the Bayesian posterior of a neural network is a challenging task due to the high-dimensionality of the parameter space. Anchored ensembles approximate the posterior by training an ensemble of neural networks on anchored losses designed for the optima to follow the Bayesian posterior. Training an ensemble, however, becomes computationally expensive as its number of members grows since the full training procedure is repeated for each member. In this note, we present Sequential Anchored Ensembles (SAE), a lightweight alternative to anchored ensembles. Instead of training each member of the ensemble from scratch, the members are trained sequentially on losses sampled with high auto-correlation, hence enabling fast convergence of the neural networks and efficient approximation of the Bayesian posterior. SAE outperform anchored ensembles, for a given computational budget, on some benchmarks while showing comparable performance on the others and achieved 2nd and 3rd place in the light and extended tracks of the NeurIPS 2021 Approximate Inference in Bayesian Deep Learning competition

Balancing Simulation-based Inference for Conservative Posteriors

Conservative inference is a major concern in simulation-based inference. It has been shown that commonly used algorithms can produce overconfident posterior approximations. Balancing has empirically proven to be an effective way to mitigate this issue. However, its application remains limited to neural ratio estimation. In this work, we extend balancing to any algorithm that provides a posterior density. In particular, we introduce a balanced version of both neural posterior estimation and contrastive neural ratio estimation. We show empirically that the balanced versions tend to produce conservative posterior approximations on a wide variety of benchmarks. In addition, we provide an alternative interpretation of the balancing condition in terms of the $\chi^2$ divergence

Stéréo multi-vues : erreur de reprojection et maillages triangulaires

National audienceCet article propose une méthode variationnelle basée sur les maillages pour la reconstruction 3D de scènes (forme et radiance) à partir de plusieurs images. Notre méthode est basée sur les modèles génératifs et minimise l'erreur de reprojection (différence entre une image observée et une image obtenue à partir de la reconstruction) par une descente de gradient. Pour la première fois, nous calculons le gradient de l'erreur de reprojection pour des surfaces non lisses représentées de manière discrète par des maillages triangulés. Le gradient prend correctement en compte les changements de visibilité qui apparaissent lorsque la surface bouge durant l'évolution ; cela force les contours occultants générés par la surface à correspondre parfaitement aux contours apparents dans les images observées. Notre méthode est capable de retrouver la forme et la radiance de diverses scènes

Minimizing the Multi-view Stereo Reprojection Error for Triangular Surface Meshes

International audienceThis article proposes a variational multi-view stereo vision method based on meshes for recovering 3D scenes (shape and radiance) from images. Our method is based on generative models and minimizes the reprojection error (difference between the observed images and the images synthesized from the reconstruction). Our contributions are twofold. 1) For the first time, we rigorously compute the gradient of the reprojection error for non smooth surfaces defined by discrete triangular meshes. The gradient correctly takes into account the visibility changes that occur when a surface moves; this forces the contours generated by the reconstructed surface to perfectly match with the apparent contours in the input images. 2) We propose an original modification of the Lambertian model to take into account deviations from the constant brightness assumption without explicitly modelling the reflectance properties of the scene or other photometric phenomena involved by the camera model. Our method is thus able to recover the shape and the diffuse radiance of non Lambertian scenes

Lightning-Fast Gravitational Wave Parameter Inference through Neural Amortization

Gravitational waves from compact binaries measured by the LIGO and Virgo detectors are routinely analyzed using Markov Chain Monte Carlo sampling algorithms. Because the evaluation of the likelihood function requires evaluating millions of waveform models that link between signal shapes and the source parameters, running Markov chains until convergence is typically expensive and requires days of computation. In this extended abstract, we provide a proof of concept that demonstrates how the latest advances in neural simulation-based inference can speed up the inference time by up to three orders of magnitude -- from days to minutes -- without impairing the performance. Our approach is based on a convolutional neural network modeling the likelihood-to-evidence ratio and entirely amortizes the computation of the posterior. We find that our model correctly estimates credible intervals for the parameters of simulated gravitational waves.Comment: V1: First version; V2: Updated references; V3: Update references and camera-ready version; V4: Correct figure labels; V5: Updated reference

Multiview Projectors/Cameras System for 3D Reconstruction of Dynamic Scenes

International audienceActive vision systems are usually limited to either partial or static scene reconstructions. In this paper, we propose to acquire the entire 3D shape of a dynamic scene. This is performed using a multiple projectors and cameras system, that allows to recover the entire shape of the object within a single scan at each frame. Like previous approaches, a static and simple pattern is used to avoid interferences of multiple patterns projected on the same object. In this paper, we extend the technique to capture a dense entire shape of a moving object with accuracy and high video frame rate. To achieve this, we mainly propose two additional steps; one is checking the consistency between the multiple cameras and projectors, and the other is an algorithm for light sectioning based on a plane parameter optimization. In addition, we also propose efficient noise reduction and mesh generation algorithm which are necessary for practical applications. In the experiments, we show that we can successfully reconstruct dense entire shapes of moving objects. Results are illustrated on real data from a system composed of six projectors and six cameras that was actually built

Averting A Crisis In Simulation-Based Inference

We present extensive empirical evidence showing that current Bayesian simulation-based inference algorithms are inadequate for the falsificationist methodology of scientific inquiry. Our results collected through months of experimental computations show that all benchmarked algorithms - (s)npe, (s)nre, snl and variants of abc – may produce overconfident posterior approximations, which makes them demonstrably unreliable and dangerous if one’s scientific goal is to constrain parameters of interest. We believe that failing to address this issue will lead to a well-founded trust crisis in simulation-based inference. For this reason, we argue that research efforts should now consider theoretical and methodological developments of conservative approximate inference algorithms and present research directions towards this objective. In this regard, we show empirical evidence that ensembles are consistently more reliable

Contribución al conocimiento de la flora vascular de la Reserva Biológica Huilo Huilo, Región de Los Ríos, Chile

Although state Reserves play a major role in biodiversity conservation, private Reserves may play a complementary role by increasing surface and ecological representation. The Reserva Biologica Huilo Huilo occupies an area of 100 000 ha and is situated in the temperate austral forest ecoregion of South America and includes Nothofagus forests and various types of high Andean vegetation. The Reserve is located at Región de Los Ríos, near the locality of Neltume (39°51’S-71°57’W) at 500 - 2000 m altitude. The results reported were obtained within an area of 11 x 20 km. Specific richness was 406 of vascular plant species belonging to 95 families and 230 genera. The richest families were asteraceae (60 species, 14.8%), poaceae (43 species, 10.6%), cyperaceae (21 species, 5.1%) and hymenophyllaceae (16 species, 3.9%). the richest genera were Hymenophyllum (13 species), Carex and Senecio (9 species each). Alien species constituted 16.3% of the total and native species 83.7%, of which 79 % are endemic to Chile and Argentina and 6 % only to Chile. The Chilean endemics with most restricted distributions are Elaphoglossum fonkii (Lomariopsidae, Pteridophyta) exclusive of Regiones de Los Ríos and de Los Lagos, and Ercilla syncarpellata (Phytolaccaceae) from Región de La Araucanía, de Los Ríos and de Los Lagos. Primula comberi (Primulaceae) and Oenothera stricta var. altissima (Onagraceae) are reported as a new species for Chile. We report for the first time Trichomanes exsectum at the cordillera de los Andes; Ranunculus hydrophilus is mentioned for the first time at Region de Los Ríos; finally distribution areas were enlarged for Epilobium densifolium (a new southern limit in Chile) and Lycopodium alboffii (a new northern limit in Chile). Hemikryptophyta is the richest taxon with Raunkiaer’s life form (60 %), followed by macrophanerophyta (11.3%) and nanopanerophyta (11 %). Eighteen species are classified as threatened, most notably Greigia pearcei (Bromeliaceae), Elaphoglossum fonkii (Lomariopsidaceae), Fascicularia bicolor (Bromeliaceae), Libertia tricocca (Iridaceae) and Trichomanes exsectum (Hymenophyllaceae). About 82.3 % of plant families and 77 % of the genera of the austral temperate South American forest are represented at Reserva Biológica Huilo Huilo. Genera of the Pteridophyta and Magnoliopsida s.l. are the best represented with 82.6% and 76 %, respectively. The Valdivian type forest is the richest community (136 species), followed by Nothofagus dombeyi forest (96 species), Nothofagus antarctica forest (45 species) and Nothofagus pumilio forest (34 species). The Valdivian type forest, although occupying a relatively small area is that with the highest species richness.Las áreas protegidas estatales juegan un papel decisivo en la conservación de la naturaleza; marco en que las reservas privadas son aliadas importantes, pues mejoran su representatividad y aumentan su superficie. La Reserva Biológica Huilo Huilo se encuentra en la ecorregión de los bosques templados del sur de Sudamérica e incluye diversos tipos de bosques de Nothofagus y vegetación andina. Se ubica en la Región de Los Ríos, localidad de Neltume (39°51’S-71°57’W) entre 500 y 2.000 m altitud. Los resultados corresponden al estudio de un cuadrante de ca. 11 x 20 km. La riqueza de la flora vascular alcanza a 406 especies, que se distribuyen en 95 familias y 230 géneros. Las familias con más especies son: Asteraceae, con 60 (14,8% del total); Poaceae, con 43 (10,6%); Cyperaceae, con 21 (5,1%) e Hymenophyllaceae con 16 (3,9%). Entre los géneros destacan por riqueza, Hymenophyllum con 13 especies; Carex y Senecio con 9; Agrostis, Baccharis y Ranunculus con 7. La mayor parte de las especies son nativas: 340 (83,7%); las alóctonas asilvestradas alcanzan a 66 (16,3%). Entre las nativas, predominan las plantas endémicas de Chile y Argentina, con 266 especies (78,2% del total de nativas); seguidas por las nativas, no endémicas ni de Chile ni de Argentina, con 54 (15,9%) y las endémicas de Chile, con 20 (5,9%). Entre las endémicas de Chile, Elaphoglossum fonkii (Lomariopsidae, Pteridophyta) es exclusiva de las Regiones de Los Ríos y de Los Lagos, y Ercilla syncarpellata (Phytolaccaceae) se ha recolectado entre las Regiones de La Araucanía y de Los Lagos. Primula comberi (Primulaceae) es nueva para Chile, lo mismo que Oenothera stricta var. altissima (Onagraceae). Se amplía la distribución de Trichomanes exsectum (Hymenophyllaceae) que no era conocido para la cordillera de los Andes, de Lycopodium alboffii (Lycopodiaceae), nuevo límite norte de distribución, de Epilobium densifolium (Onagraceae), también con un nuevo límite sur y la de Ranunculus hydrophilus (Ranunculaceae), primera mención para la Región de Los Ríos. Entre las formas de vida predominan los hemicriptófitos con un 60%, seguidos por los fanerófitos, con 11,3% y los nanofanerófitos, con 11 %. Se encontraron 18 especies que han sido incluidas en alguna categoría de amenaza, las más destacadas Greigia pearcei (Bromeliaceae), Elaphoglossum fonkii (Lomariopsidaceae), Fascicularia bicolor (Bromeliaceae), Libertia tricocca (Iridaceae) y Trichomanes exsectum (Hymenophyllaceae). Un 82,3% de las familias y un 77% de los géneros de los bosques australes templados de Sudamérica están representados en la reserva. Al nivel de riqueza por comunidad, el bosque valdiviano es el más rico con 136 de las 337 especies nativas del área de estudio; lo siguen los de Nothofagus dombeyi (coigüe), con 96; el de Nothofagus antarctica (ñirre), con 45 y el de Nothofagus pumilio (lenga) con 34. Dado que la riqueza está relacionada con la superficie, es notable que el bosque de tipo valdiviano, que es uno de los que ocupa la menor superficie, tenga la riqueza más alta