969 research outputs found
Graphs, Matrices, and the GraphBLAS: Seven Good Reasons
The analysis of graphs has become increasingly important to a wide range of
applications. Graph analysis presents a number of unique challenges in the
areas of (1) software complexity, (2) data complexity, (3) security, (4)
mathematical complexity, (5) theoretical analysis, (6) serial performance, and
(7) parallel performance. Implementing graph algorithms using matrix-based
approaches provides a number of promising solutions to these challenges. The
GraphBLAS standard (istc- bigdata.org/GraphBlas) is being developed to bring
the potential of matrix based graph algorithms to the broadest possible
audience. The GraphBLAS mathematically defines a core set of matrix-based graph
operations that can be used to implement a wide class of graph algorithms in a
wide range of programming environments. This paper provides an introduction to
the GraphBLAS and describes how the GraphBLAS can be used to address many of
the challenges associated with analysis of graphs.Comment: 10 pages; International Conference on Computational Science workshop
on the Applications of Matrix Computational Methods in the Analysis of Modern
Dat
Enabling Massive Deep Neural Networks with the GraphBLAS
Deep Neural Networks (DNNs) have emerged as a core tool for machine learning.
The computations performed during DNN training and inference are dominated by
operations on the weight matrices describing the DNN. As DNNs incorporate more
stages and more nodes per stage, these weight matrices may be required to be
sparse because of memory limitations. The GraphBLAS.org math library standard
was developed to provide high performance manipulation of sparse weight
matrices and input/output vectors. For sufficiently sparse matrices, a sparse
matrix library requires significantly less memory than the corresponding dense
matrix implementation. This paper provides a brief description of the
mathematics underlying the GraphBLAS. In addition, the equations of a typical
DNN are rewritten in a form designed to use the GraphBLAS. An implementation of
the DNN is given using a preliminary GraphBLAS C library. The performance of
the GraphBLAS implementation is measured relative to a standard dense linear
algebra library implementation. For various sizes of DNN weight matrices, it is
shown that the GraphBLAS sparse implementation outperforms a BLAS dense
implementation as the weight matrix becomes sparser.Comment: 10 pages, 7 figures, to appear in the 2017 IEEE High Performance
Extreme Computing (HPEC) conferenc
Eriksson's numbers game and finite Coxeter groups
The numbers game is a one-player game played on a finite simple graph with
certain ``amplitudes'' assigned to its edges and with an initial assignment of
real numbers to its nodes. The moves of the game successively transform the
numbers at the nodes using the amplitudes in a certain way. This game and its
interactions with Coxeter/Weyl group theory and Lie theory have been studied by
many authors. In particular, Eriksson connects certain geometric
representations of Coxeter groups with games on graphs with certain real number
amplitudes. Games played on such graphs are ``E-games.'' Here we investigate
various finiteness aspects of E-game play: We extend Eriksson's work relating
moves of the game to reduced decompositions of elements of a Coxeter group
naturally associated to the game graph. We use Stembridge's theory of fully
commutative Coxeter group elements to classify what we call here the
``adjacency-free'' initial positions for finite E-games. We characterize when
the positive roots for certain geometric representations of finite Coxeter
groups can be obtained from E-game play. Finally, we provide a new Dynkin
diagram classification result of E-game graphs meeting a certain finiteness
requirement.Comment: 18 page
Pivots, Determinants, and Perfect Matchings of Graphs
We give a characterization of the effect of sequences of pivot operations on
a graph by relating it to determinants of adjacency matrices. This allows us to
deduce that two sequences of pivot operations are equivalent iff they contain
the same set S of vertices (modulo two). Moreover, given a set of vertices S,
we characterize whether or not such a sequence using precisely the vertices of
S exists. We also relate pivots to perfect matchings to obtain a
graph-theoretical characterization. Finally, we consider graphs with self-loops
to carry over the results to sequences containing both pivots and local
complementation operations.Comment: 16 page
Regular quantum graphs
We introduce the concept of regular quantum graphs and construct connected
quantum graphs with discrete symmetries. The method is based on a decomposition
of the quantum propagator in terms of permutation matrices which control the
way incoming and outgoing channels at vertex scattering processes are
connected. Symmetry properties of the quantum graph as well as its spectral
statistics depend on the particular choice of permutation matrices, also called
connectivity matrices, and can now be easily controlled. The method may find
applications in the study of quantum random walks networks and may also prove
to be useful in analysing universality in spectral statistics.Comment: 12 pages, 3 figure
From conformal embeddings to quantum symmetries: an exceptional SU(4) example
We briefly discuss several algebraic tools that are used to describe the
quantum symmetries of Boundary Conformal Field Theories on a torus. The
starting point is a fusion category, together with an action on another
category described by a quantum graph. For known examples, the corresponding
modular invariant partition function, which is sometimes associated with a
conformal embedding, provides enough information to recover the whole
structure. We illustrate these notions with the example of the conformal
embedding of SU(4) at level 4 into Spin(15) at level 1, leading to the
exceptional quantum graph E4(SU(4)).Comment: 22 pages, 3 color figures. Version 2: We changed the color of figures
(ps files) in such a way that they are still understood when converted to
gray levels. Version 3: Several references have been adde
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