37 research outputs found
Efficient Implementation of a Synchronous Parallel Push-Relabel Algorithm
Motivated by the observation that FIFO-based push-relabel algorithms are able
to outperform highest label-based variants on modern, large maximum flow
problem instances, we introduce an efficient implementation of the algorithm
that uses coarse-grained parallelism to avoid the problems of existing parallel
approaches. We demonstrate good relative and absolute speedups of our algorithm
on a set of large graph instances taken from real-world applications. On a
modern 40-core machine, our parallel implementation outperforms existing
sequential implementations by up to a factor of 12 and other parallel
implementations by factors of up to 3
Variations on the Stochastic Shortest Path Problem
In this invited contribution, we revisit the stochastic shortest path
problem, and show how recent results allow one to improve over the classical
solutions: we present algorithms to synthesize strategies with multiple
guarantees on the distribution of the length of paths reaching a given target,
rather than simply minimizing its expected value. The concepts and algorithms
that we propose here are applications of more general results that have been
obtained recently for Markov decision processes and that are described in a
series of recent papers.Comment: Invited paper for VMCAI 201
Revisiting the scaling of the specific heat of the three-dimensional random-field Ising model
We revisit the scaling behavior of the specific heat of the three-dimensional
random-field Ising model with a Gaussian distribution of the disorder. Exact ground states
of the model are obtained using graph-theoretical algorithms for different strengths
= 268 3Â spins. By numerically differentiating the bond energy
with respect to h, a specific-heat-like quantity is obtained whose
maximum is found to converge to a constant in the thermodynamic limit. Compared to a
previous study following the same approach, we have studied here much larger system sizes
with an increased statistical accuracy. We discuss the relevance of our results under the
prism of a modified Rushbrooke inequality for the case of a saturating specific heat.
Finally, as a byproduct of our analysis, we provide high-accuracy estimates of the
critical field hc =
2.279(7) and the critical exponent of the correlation exponent
Μ =
1.37(1), in excellent agreement to the most recent computations in the
literature
Adaptive large neighborhood search for the vehicle routing problem with synchronization constraints at the delivery location
What Do We Learn from Experimental Algorithmics?
Experimental Algorithmics is concerned with the design, implementation, tuning, debugging and performance analysis of computer programs for solving algorithmic problems. It provides methodologies and tools for designing, developing and experimentally analyzing efficient algorithmic codes and aims at integrating and reinforcing traditional theoretical approaches for the design and analysis of algorithms and data structures. In this paper we survey some relevant contributions to the field of Experimental Algorithmics and we discuss significant examples where the experimental approach helped in developing new ideas, in assessing heuristics and techniques, and in gaining a deeper insight about existing algorithms.