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Network-Oblivious Algorithms

The design of algorithms that can run unchanged yet efficiently on a variety of machines characterized by different degrees of parallelism and communication capabilities is a highly desirable goal. We propose a framework for network-obliviousness based on a model of computation where the only parameter is the problems input size. Algorithms are then evaluated on a model with two parameters, capturing parallelism and granularity of communication. We show that, for a wide class of network-oblivious algorithms, optimality in the latter model implies optimality in a block-variant of the decomposable BSP model, which effectively describes a wide and significant class of parallel platforms. We illustrate our framework by providing optimal network-oblivious algorithms for a few key problems, and also establish some negative results.

A lower bound technique for communication on BSP with application to the FFT

Communication complexity is defined, within the Bulk Synchronous Parallel (BSP) model of computation, as the sum of the degrees of all the supersteps. A lower bound to the communication complexity is derived for a given class of DAG computations in terms of the switching potential of a DAG, that is, the number of permutations that the DAG can realize when viewed as a switching network. The proposed technique yields a novel and tight lower bound for the FFT graph.

Communication Lower Bounds for Distributed-Memory Computations

We present space-efficient parallel strategies for two fundamental combinatorial search problems, namely, backtrack search and branch-and-bound, both involving the visit of an

A time- and message-optimal distributed algorithm for minimum spanning trees

n

Chasing Convex Bodies and Functions

-node tree of height

A o(n)-Competitive Deterministic Algorithm for Online Matching on a Line

h

Efficient Computation of Optimal Energy and Fractional Weighted Flow Trade-off Schedules

under the assumption that a node can be accessed only through its father or its children. For both problems we propose efficient algorithms that run on a

Message Lower Bounds via Efficient Network Synchronization

p

On the Complexity of Speed Scaling

-processor distributed-memory machine. For backtrack search, we give a deterministic algorithm running in

Energy-efficient circuit design

O(n/p+h\log p)