5,325 research outputs found
Dimensionality Reduction for k-Means Clustering and Low Rank Approximation
We show how to approximate a data matrix with a much smaller
sketch that can be used to solve a general class of
constrained k-rank approximation problems to within error.
Importantly, this class of problems includes -means clustering and
unconstrained low rank approximation (i.e. principal component analysis). By
reducing data points to just dimensions, our methods generically
accelerate any exact, approximate, or heuristic algorithm for these ubiquitous
problems.
For -means dimensionality reduction, we provide relative
error results for many common sketching techniques, including random row
projection, column selection, and approximate SVD. For approximate principal
component analysis, we give a simple alternative to known algorithms that has
applications in the streaming setting. Additionally, we extend recent work on
column-based matrix reconstruction, giving column subsets that not only `cover'
a good subspace for \bv{A}, but can be used directly to compute this
subspace.
Finally, for -means clustering, we show how to achieve a
approximation by Johnson-Lindenstrauss projecting data points to just dimensions. This gives the first result that leverages the
specific structure of -means to achieve dimension independent of input size
and sublinear in
MPICH-G2: A Grid-Enabled Implementation of the Message Passing Interface
Application development for distributed computing "Grids" can benefit from
tools that variously hide or enable application-level management of critical
aspects of the heterogeneous environment. As part of an investigation of these
issues, we have developed MPICH-G2, a Grid-enabled implementation of the
Message Passing Interface (MPI) that allows a user to run MPI programs across
multiple computers, at the same or different sites, using the same commands
that would be used on a parallel computer. This library extends the Argonne
MPICH implementation of MPI to use services provided by the Globus Toolkit for
authentication, authorization, resource allocation, executable staging, and
I/O, as well as for process creation, monitoring, and control. Various
performance-critical operations, including startup and collective operations,
are configured to exploit network topology information. The library also
exploits MPI constructs for performance management; for example, the MPI
communicator construct is used for application-level discovery of, and
adaptation to, both network topology and network quality-of-service mechanisms.
We describe the MPICH-G2 design and implementation, present performance
results, and review application experiences, including record-setting
distributed simulations.Comment: 20 pages, 8 figure
GibbsCluster: unsupervised clustering and alignment of peptide sequences
Receptor interactions with short linear peptide fragments (ligands) are at the base of many biological signaling processes. Conserved and information-rich amino acid patterns, commonly called sequence motifs, shape and regulate these interactions. Because of the properties of a receptor-ligand system or of the assay used to interrogate it, experimental data often contain multiple sequence motifs. GibbsCluster is a powerful tool for unsupervised motif discovery because it can simultaneously cluster and align peptide data. The GibbsCluster 2.0 presented here is an improved version incorporating insertion and deletions accounting for variations in motif length in the peptide input. In basic terms, the program takes as input a set of peptide sequences and clusters them into meaningful groups. It returns the optimal number of clusters it identified, together with the sequence alignment and sequence motif characterizing each cluster. Several parameters are available to customize cluster analysis, including adjustable penalties for small clusters and overlapping groups and a trash cluster to remove outliers. As an example application, we used the server to deconvolute multiple specificities in large-scale peptidome data generated by mass spectrometry.Fil: Andreatta, Massimo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Biotecnológicas. Instituto de Investigaciones Biotecnológicas "Dr. Raúl Alfonsín" (sede Chascomús). Universidad Nacional de San Martín. Instituto de Investigaciones Biotecnológicas. Instituto de Investigaciones Biotecnológicas "Dr. Raúl Alfonsín" (sede Chascomús); ArgentinaFil: Alvarez, Bruno. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Biotecnológicas. Instituto de Investigaciones Biotecnológicas "Dr. Raúl Alfonsín" (sede Chascomús). Universidad Nacional de San Martín. Instituto de Investigaciones Biotecnológicas. Instituto de Investigaciones Biotecnológicas "Dr. Raúl Alfonsín" (sede Chascomús); ArgentinaFil: Nielsen, Morten. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Biotecnológicas. Instituto de Investigaciones Biotecnológicas "Dr. Raúl Alfonsín" (sede Chascomús). Universidad Nacional de San Martín. Instituto de Investigaciones Biotecnológicas. Instituto de Investigaciones Biotecnológicas "Dr. Raúl Alfonsín" (sede Chascomús); Argentina. Technical University of Denmark; Dinamarc
M22: A Communication-Efficient Algorithm for Federated Learning Inspired by Rate-Distortion
In federated learning (FL), the communication constraint between the remote
learners and the Parameter Server (PS) is a crucial bottleneck. For this
reason, model updates must be compressed so as to minimize the loss in accuracy
resulting from the communication constraint. This paper proposes ``\emph{-magnitude weighted distortion + degrees of freedom''}
(M22) algorithm, a rate-distortion inspired approach to gradient compression
for federated training of deep neural networks (DNNs). In particular, we
propose a family of distortion measures between the original gradient and the
reconstruction we referred to as ``-magnitude weighted '' distortion,
and we assume that gradient updates follow an i.i.d. distribution --
generalized normal or Weibull, which have two degrees of freedom. In both the
distortion measure and the gradient, there is one free parameter for each that
can be fitted as a function of the iteration number. Given a choice of gradient
distribution and distortion measure, we design the quantizer minimizing the
expected distortion in gradient reconstruction. To measure the gradient
compression performance under a communication constraint, we define the
\emph{per-bit accuracy} as the optimal improvement in accuracy that one bit of
communication brings to the centralized model over the training period. Using
this performance measure, we systematically benchmark the choice of gradient
distribution and distortion measure. We provide substantial insights on the
role of these choices and argue that significant performance improvements can
be attained using such a rate-distortion inspired compressor.Comment: arXiv admin note: text overlap with arXiv:2202.0281
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Clades of huge phages from across Earth's ecosystems.
Bacteriophages typically have small genomes1 and depend on their bacterial hosts for replication2. Here we sequenced DNA from diverse ecosystems and found hundreds of phage genomes with lengths of more than 200 kilobases (kb), including a genome of 735 kb, which is-to our knowledge-the largest phage genome to be described to date. Thirty-five genomes were manually curated to completion (circular and no gaps). Expanded genetic repertoires include diverse and previously undescribed CRISPR-Cas systems, transfer RNAs (tRNAs), tRNA synthetases, tRNA-modification enzymes, translation-initiation and elongation factors, and ribosomal proteins. The CRISPR-Cas systems of phages have the capacity to silence host transcription factors and translational genes, potentially as part of a larger interaction network that intercepts translation to redirect biosynthesis to phage-encoded functions. In addition, some phages may repurpose bacterial CRISPR-Cas systems to eliminate competing phages. We phylogenetically define the major clades of huge phages from human and other animal microbiomes, as well as from oceans, lakes, sediments, soils and the built environment. We conclude that the large gene inventories of huge phages reflect a conserved biological strategy, and that the phages are distributed across a broad bacterial host range and across Earth's ecosystems
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