5 Search Results for "Johnson, Christopher R."

Document
DOI: 10.4230/DagRep.12.8.1
Visualization and Decision Making Design Under Uncertainty (Dagstuhl Seminar 22331)

Authors: Nadia Boukhelifa, Christopher R. Johnson, and Kristi Potter

Published in: Dagstuhl Reports, Volume 12, Issue 8 (2023)

Abstract
This report documents the program and the outcomes of Dagstuhl Seminar 22331 "Visualization and Decision Making Design Under Uncertainty". The seminar brought together 33 researchers and practitioners from different domains concerned with visualization and decision making under uncertainty including visualization, visual analytics, human-computer interaction, artificial intelligence, climate research, geography and geology. The programme was organized in two parts: In the first part which lasted two days, participants gave short talks where they discussed current practices and the uncertainty visualization challenges they encountered in their own research. At the end of day two, participants brainstormed collectively around the main uncertainty visualization research challenges across domains and applications. In the second part, participants voted for the following three main challenges they wished to discuss for the remainder of the seminar (one and a half days): applications, human-centered uncertainty visualization, a design process for uncertainty visualization. Thus three break-out groups were formed to discuss these challenges. Abstracts for the individual talks and the break-out group activities are included in this report.
Cite as

Nadia Boukhelifa, Christopher R. Johnson, and Kristi Potter. Visualization and Decision Making Design Under Uncertainty (Dagstuhl Seminar 22331). In Dagstuhl Reports, Volume 12, Issue 8, pp. 1-19, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2023)

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@Article{boukhelifa_et_al:DagRep.12.8.1,
  author =	{Boukhelifa, Nadia and Johnson, Christopher R. and Potter, Kristi},
  title =	{{Visualization and Decision Making Design Under Uncertainty (Dagstuhl Seminar 22331)}},
  pages =	{1--19},
  journal =	{Dagstuhl Reports},
  ISSN =	{2192-5283},
  year =	{2023},
  volume =	{12},
  number =	{8},
  editor =	{Boukhelifa, Nadia and Johnson, Christopher R. and Potter, Kristi},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops-dev.dagstuhl.de/entities/document/10.4230/DagRep.12.8.1},
  URN =		{urn:nbn:de:0030-drops-177120},
  doi =		{10.4230/DagRep.12.8.1},
  annote =	{Keywords: Decision making, Uncertainty visualization, Visual Analytics, Visualization}
}
Document
DOI: 10.4230/LIPIcs.ITCS.2022.82
Online Multivalid Learning: Means, Moments, and Prediction Intervals

Authors: Varun Gupta, Christopher Jung, Georgy Noarov, Mallesh M. Pai, and Aaron Roth

Published in: LIPIcs, Volume 215, 13th Innovations in Theoretical Computer Science Conference (ITCS 2022)

Abstract
We present a general, efficient technique for providing contextual predictions that are "multivalid" in various senses, against an online sequence of adversarially chosen examples (x,y). This means that the resulting estimates correctly predict various statistics of the labels y not just marginally - as averaged over the sequence of examples - but also conditionally on x ∈ G for any G belonging to an arbitrary intersecting collection of groups 𝒢. We provide three instantiations of this framework. The first is mean prediction, which corresponds to an online algorithm satisfying the notion of multicalibration from [Hébert-Johnson et al., 2018]. The second is variance and higher moment prediction, which corresponds to an online algorithm satisfying the notion of mean-conditioned moment multicalibration from [Jung et al., 2021]. Finally, we define a new notion of prediction interval multivalidity, and give an algorithm for finding prediction intervals which satisfy it. Because our algorithms handle adversarially chosen examples, they can equally well be used to predict statistics of the residuals of arbitrary point prediction methods, giving rise to very general techniques for quantifying the uncertainty of predictions of black box algorithms, even in an online adversarial setting. When instantiated for prediction intervals, this solves a similar problem as conformal prediction, but in an adversarial environment and with multivalidity guarantees stronger than simple marginal coverage guarantees.
Cite as

Varun Gupta, Christopher Jung, Georgy Noarov, Mallesh M. Pai, and Aaron Roth. Online Multivalid Learning: Means, Moments, and Prediction Intervals. In 13th Innovations in Theoretical Computer Science Conference (ITCS 2022). Leibniz International Proceedings in Informatics (LIPIcs), Volume 215, pp. 82:1-82:24, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2022)

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@InProceedings{gupta_et_al:LIPIcs.ITCS.2022.82,
  author =	{Gupta, Varun and Jung, Christopher and Noarov, Georgy and Pai, Mallesh M. and Roth, Aaron},
  title =	{{Online Multivalid Learning: Means, Moments, and Prediction Intervals}},
  booktitle =	{13th Innovations in Theoretical Computer Science Conference (ITCS 2022)},
  pages =	{82:1--82:24},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-217-4},
  ISSN =	{1868-8969},
  year =	{2022},
  volume =	{215},
  editor =	{Braverman, Mark},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops-dev.dagstuhl.de/entities/document/10.4230/LIPIcs.ITCS.2022.82},
  URN =		{urn:nbn:de:0030-drops-156785},
  doi =		{10.4230/LIPIcs.ITCS.2022.82},
  annote =	{Keywords: Uncertainty Estimation, Calibration, Online Learning}
}
Document
DOI: 10.4230/LIPIcs.ESA.2021.61
Finding an Approximate Mode of a Kernel Density Estimate

Authors: Jasper C.H. Lee, Jerry Li, Christopher Musco, Jeff M. Phillips, and Wai Ming Tai

Published in: LIPIcs, Volume 204, 29th Annual European Symposium on Algorithms (ESA 2021)

Abstract
Given points P = {p₁,...,p_n} subset of ℝ^d, how do we find a point x which approximately maximizes the function 1/n ∑_{p_i ∈ P} e^{-‖p_i-x‖²}? In other words, how do we find an approximate mode of a Gaussian kernel density estimate (KDE) of P? Given the power of KDEs in representing probability distributions and other continuous functions, the basic mode finding problem is widely applicable. However, it is poorly understood algorithmically. We provide fast and provably accurate approximation algorithms for mode finding in both the low and high dimensional settings. For low (constant) dimension, our main contribution is a reduction to solving systems of polynomial inequalities. For high dimension, we prove the first dimensionality reduction result for KDE mode finding. The latter result leverages Johnson-Lindenstrauss projection, Kirszbraun’s classic extension theorem, and perhaps surprisingly, the mean-shift heuristic for mode finding. For constant approximation factor these algorithms run in O(n (log n)^{O(d)}) and O(nd + (log n)^{O(log³ n)}), respectively; these are proven more precisely as a (1+ε)-approximation guarantee. Furthermore, for the special case of d = 2, we give a combinatorial algorithm running in O(n log² n) time. We empirically demonstrate that the random projection approach and the 2-dimensional algorithm improves over the state-of-the-art mode-finding heuristics.
Cite as

Jasper C.H. Lee, Jerry Li, Christopher Musco, Jeff M. Phillips, and Wai Ming Tai. Finding an Approximate Mode of a Kernel Density Estimate. In 29th Annual European Symposium on Algorithms (ESA 2021). Leibniz International Proceedings in Informatics (LIPIcs), Volume 204, pp. 61:1-61:19, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2021)

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@InProceedings{lee_et_al:LIPIcs.ESA.2021.61,
  author =	{Lee, Jasper C.H. and Li, Jerry and Musco, Christopher and Phillips, Jeff M. and Tai, Wai Ming},
  title =	{{Finding an Approximate Mode of a Kernel Density Estimate}},
  booktitle =	{29th Annual European Symposium on Algorithms (ESA 2021)},
  pages =	{61:1--61:19},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-204-4},
  ISSN =	{1868-8969},
  year =	{2021},
  volume =	{204},
  editor =	{Mutzel, Petra and Pagh, Rasmus and Herman, Grzegorz},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops-dev.dagstuhl.de/entities/document/10.4230/LIPIcs.ESA.2021.61},
  URN =		{urn:nbn:de:0030-drops-146428},
  doi =		{10.4230/LIPIcs.ESA.2021.61},
  annote =	{Keywords: Kernel density estimation, Dimensionality reduction, Coresets, Means-shift}
}
Document
DOI: 10.4230/LIPIcs.ITCS.2017.53
Fast Cross-Polytope Locality-Sensitive Hashing

Authors: Christopher Kennedy and Rachel Ward

Published in: LIPIcs, Volume 67, 8th Innovations in Theoretical Computer Science Conference (ITCS 2017)

Abstract
We provide a variant of cross-polytope locality sensitive hashing with respect to angular distance which is provably optimal in asymptotic sensitivity and enjoys \mathcal{O}(d \ln d ) hash computation time. Building on a recent result in (Andoni, Indyk, Laarhoven, Razenshteyn '15), we show that optimal asymptotic sensitivity for cross-polytope LSH is retained even when the dense Gaussian matrix is replaced by a fast Johnson-Lindenstrauss transform followed by discrete pseudo-rotation, reducing the hash computation time from \mathcal{O}(d^2) to \mathcal{O}(d \ln d ). Moreover, our scheme achieves the optimal rate of convergence for sensitivity. By incorporating a low-randomness Johnson-Lindenstrauss transform, our scheme can be modified to require only \mathcal{O}(\ln^9(d)) random bits.
Cite as

Christopher Kennedy and Rachel Ward. Fast Cross-Polytope Locality-Sensitive Hashing. In 8th Innovations in Theoretical Computer Science Conference (ITCS 2017). Leibniz International Proceedings in Informatics (LIPIcs), Volume 67, pp. 53:1-53:16, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2017)

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@InProceedings{kennedy_et_al:LIPIcs.ITCS.2017.53,
  author =	{Kennedy, Christopher and Ward, Rachel},
  title =	{{Fast Cross-Polytope Locality-Sensitive Hashing}},
  booktitle =	{8th Innovations in Theoretical Computer Science Conference (ITCS 2017)},
  pages =	{53:1--53:16},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-029-3},
  ISSN =	{1868-8969},
  year =	{2017},
  volume =	{67},
  editor =	{Papadimitriou, Christos H.},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops-dev.dagstuhl.de/entities/document/10.4230/LIPIcs.ITCS.2017.53},
  URN =		{urn:nbn:de:0030-drops-81936},
  doi =		{10.4230/LIPIcs.ITCS.2017.53},
  annote =	{Keywords: Locality-sensitive hashing, Dimension reduction, Johnson-Lindenstrauss lemma}
}
Document
DOI: 10.4230/DagSemRep.370
Challenges in High Performance Simulations for Science and Engineering (Dagstuhl Seminar 03111)

Authors: Friedel Hoßfeld, Christopher R. Johnson, Hans Petter, and Unlrich Rüde

Published in: Dagstuhl Seminar Reports. Dagstuhl Seminar Reports, Volume 1 (2021)

Abstract
Cite as

Friedel Hoßfeld, Christopher R. Johnson, Hans Petter, and Unlrich Rüde. Challenges in High Performance Simulations for Science and Engineering (Dagstuhl Seminar 03111). Dagstuhl Seminar Report 370, pp. 1-5, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2003)

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@TechReport{hofeld_et_al:DagSemRep.370,
  author =	{Ho{\ss}feld, Friedel and Johnson, Christopher R. and Petter, Hans and R\"{u}de, Unlrich},
  title =	{{Challenges in High Performance Simulations for Science and Engineering (Dagstuhl Seminar 03111)}},
  pages =	{1--5},
  ISSN =	{1619-0203},
  year =	{2003},
  type = 	{Dagstuhl Seminar Report},
  number =	{370},
  institution =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops-dev.dagstuhl.de/entities/document/10.4230/DagSemRep.370},
  URN =		{urn:nbn:de:0030-drops-152509},
  doi =		{10.4230/DagSemRep.370},
}
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