81,282 research outputs found
On dynamic breadth-first search in external-memory
We provide the first non-trivial result on dynamic breadth-first search (BFS) in external-memory: For general sparse undirected graphs of initially nodes and O(n) edges and monotone update sequences of either edge insertions or edge deletions, we prove an amortized high-probability bound of O(n/B^{2/3}+\sort(n)\cdot \log B) I/Os per update. In contrast, the currently best approach for static BFS on sparse undirected graphs requires \Omega(n/B^{1/2}+\sort(n)) I/Os. 1998 ACM Subject Classification: F.2.2. Key words and phrases: External Memory, Dynamic Graph Algorithms, BFS, Randomization
On Dynamic Breadth-First Search in External-Memory
We provide the first non-trivial result on dynamic breadth-first
search (BFS) in external-memory: For general sparse undirected
graphs of initially nodes and edges and monotone update
sequences of either edge insertions or edge
deletions, we prove an amortized high-probability bound of
I/Os per update. In contrast,
the currently best approach for static BFS on sparse undirected
graphs requires I/Os
Platform Dependent Verification: On Engineering Verification Tools for 21st Century
The paper overviews recent developments in platform-dependent explicit-state
LTL model checking.Comment: In Proceedings PDMC 2011, arXiv:1111.006
Designing as Construction of Representations: A Dynamic Viewpoint in Cognitive Design Research
This article presents a cognitively oriented viewpoint on design. It focuses
on cognitive, dynamic aspects of real design, i.e., the actual cognitive
activity implemented by designers during their work on professional design
projects. Rather than conceiving de-signing as problem solving - Simon's
symbolic information processing (SIP) approach - or as a reflective practice or
some other form of situated activity - the situativity (SIT) approach - we
consider that, from a cognitive viewpoint, designing is most appropriately
characterised as a construction of representations. After a critical discussion
of the SIP and SIT approaches to design, we present our view-point. This
presentation concerns the evolving nature of representations regarding levels
of abstraction and degrees of precision, the function of external
representations, and specific qualities of representation in collective design.
Designing is described at three levels: the organisation of the activity, its
strategies, and its design-representation construction activities (different
ways to generate, trans-form, and evaluate representations). Even if we adopt a
"generic design" stance, we claim that design can take different forms
depending on the nature of the artefact, and we propose some candidates for
dimensions that allow a distinction to be made between these forms of design.
We discuss the potential specificity of HCI design, and the lack of cognitive
design research occupied with the quality of design. We close our discussion of
representational structures and activities by an outline of some directions
regarding their functional linkages
Theoretically Efficient Parallel Graph Algorithms Can Be Fast and Scalable
There has been significant recent interest in parallel graph processing due
to the need to quickly analyze the large graphs available today. Many graph
codes have been designed for distributed memory or external memory. However,
today even the largest publicly-available real-world graph (the Hyperlink Web
graph with over 3.5 billion vertices and 128 billion edges) can fit in the
memory of a single commodity multicore server. Nevertheless, most experimental
work in the literature report results on much smaller graphs, and the ones for
the Hyperlink graph use distributed or external memory. Therefore, it is
natural to ask whether we can efficiently solve a broad class of graph problems
on this graph in memory.
This paper shows that theoretically-efficient parallel graph algorithms can
scale to the largest publicly-available graphs using a single machine with a
terabyte of RAM, processing them in minutes. We give implementations of
theoretically-efficient parallel algorithms for 20 important graph problems. We
also present the optimizations and techniques that we used in our
implementations, which were crucial in enabling us to process these large
graphs quickly. We show that the running times of our implementations
outperform existing state-of-the-art implementations on the largest real-world
graphs. For many of the problems that we consider, this is the first time they
have been solved on graphs at this scale. We have made the implementations
developed in this work publicly-available as the Graph-Based Benchmark Suite
(GBBS).Comment: This is the full version of the paper appearing in the ACM Symposium
on Parallelism in Algorithms and Architectures (SPAA), 201
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