scholarly journals IMPROPER COLORING OF WEIGHTED GRID AND HEXAGONAL GRAPHS

2010 ◽  
Vol 02 (03) ◽  
pp. 395-411 ◽  
Author(s):  
JEAN-CLAUDE BERMOND ◽  
FRÉDÉRIC HAVET ◽  
FLORIAN HUC ◽  
CLÁUDIA LINHARES SALES
Keyword(s):  
Approximation Algorithms ◽  
Triangular Lattice ◽  
Allocation Problem ◽  
Approximation Ratio ◽  
Exact Results ◽  
Proper Coloring ◽  
Frequency Allocation ◽  
Coloring Problem ◽  
Improper Coloring ◽  
General Graphs

We study a weighted improper coloring problem motivated by a frequency allocation problem. It consists of associating to each vertex a set of p(v) (weight) distinct colors (frequencies), such that the set of vertices having a given color induces a graph of degree at most k (the case k = 0 corresponds to proper coloring). The objective is to minimize the number of colors. We propose approximation algorithms to compute such a coloring for general graphs. We apply these to obtain good approximation ratio for grid and hexagonal graphs. Furthermore we give exact results for the 2-dimensional grid and the triangular lattice when the weights are all the same.

Approximation Algorithms for Submodular Data Summarization with a Knapsack Constraint

2021 ◽  
Vol 5 (1) ◽  
pp. 1-31
Author(s):  
Kai Han ◽  
Shuang Cui ◽  
Tianshuai Zhu ◽  
Enpei Zhang ◽  
Benwei Wu ◽  
...  
Keyword(s):  
Approximation Algorithms ◽  
Fundamental Problem ◽  
Randomized Algorithm ◽  
Deterministic Algorithm ◽  
Submodular Function ◽  
Approximation Ratio ◽  
Performance Bounds ◽  
Data Summarization ◽  
Submodular Optimization ◽  
Knapsack Constraint

Data summarization, i.e., selecting representative subsets of manageable size out of massive data, is often modeled as a submodular optimization problem. Although there exist extensive algorithms for submodular optimization, many of them incur large computational overheads and hence are not suitable for mining big data. In this work, we consider the fundamental problem of (non-monotone) submodular function maximization with a knapsack constraint, and propose simple yet effective and efficient algorithms for it. Specifically, we propose a deterministic algorithm with approximation ratio 6 and a randomized algorithm with approximation ratio 4, and show that both of them can be accelerated to achieve nearly linear running time at the cost of weakening the approximation ratio by an additive factor of ε. We then consider a more restrictive setting without full access to the whole dataset, and propose streaming algorithms with approximation ratios of 8+ε and 6+ε that make one pass and two passes over the data stream, respectively. As a by-product, we also propose a two-pass streaming algorithm with an approximation ratio of 2+ε when the considered submodular function is monotone. To the best of our knowledge, our algorithms achieve the best performance bounds compared to the state-of-the-art approximation algorithms with efficient implementation for the same problem. Finally, we evaluate our algorithms in two concrete submodular data summarization applications for revenue maximization in social networks and image summarization, and the empirical results show that our algorithms outperform the existing ones in terms of both effectiveness and efficiency.

APPROXIMATING THE NEAREST NEIGHBOR INTERCHARGE DISTANCE FOR NON-UNIFORM-DEGREE EVOLUTIONARY TREES

2001 ◽  
Vol 12 (04) ◽  
pp. 533-550 ◽  
Author(s):  
WING-KAI HON ◽  
TAK-WAH LAM
Keyword(s):  
Approximation Algorithms ◽  
Maximum Degree ◽  
Nearest Neighbor ◽  
Sufficient Conditions ◽  
Necessary And Sufficient Conditions ◽  
Approximation Ratio ◽  
Evolutionary Trees ◽  
Weighted Trees ◽  
Np Complete ◽  
Necessary And Sufficient

The nearest neighbor interchange (nni) distance is a classical metric for measuring the distance (dissimilarity) between evolutionary trees. It has been known that computing the nni distance is NP-complete. Existing approximation algorithms can attain an approximation ratio log n for unweighted trees and 4 log n for weighted trees; yet these algorithms are limited to degree-3 trees. This paper extends the study of nni distance to trees with non-uniform degrees. We formulate the necessary and sufficient conditions for nni transformation and devise more topology-sensitive approximation algorithms to handle trees with non-uniform degrees. The approximation ratios are respectively [Formula: see text] and [Formula: see text] for unweighted and weighted trees, where d ≥ 4 is the maximum degree of the input trees.

scholarly journals Grundy Number of Some Chordal Graphs

2018 ◽  
Vol 7 (4.10) ◽  
pp. 64
Author(s):  
R. Nagarathinam ◽  
N. Parvathi ◽  
. .
Keyword(s):  
Line Graph ◽  
Cartesian Product ◽  
Chordal Graphs ◽  
Complete Graphs ◽  
Proper Coloring ◽  
Coloring Problem ◽  
Grundy Number

For a given graph G and integer k, the Coloring problem is that of testing whether G has a k-coloring, that is, whether there exists a vertex mapping c : V → {1, 2, . . .} such that c(u) 12≠"> c(v) for every edge uv ∈ E. For proper coloring, colors assigned must be minimum, but for Grundy coloring which should be maximum. In this instance, Grundy numbers of chordal graphs like Cartesian product of two path graphs, join of the path and complete graphs and the line graph of tadpole have been executed 

scholarly journals Approximation Algorithms for the Interval Constrained Coloring Problem

Algorithmica ◽  
2010 ◽  
Vol 61 (2) ◽  
pp. 342-361 ◽  
Author(s):  
Ernst Althaus ◽  
Stefan Canzar ◽  
Khaled Elbassioni ◽  
Andreas Karrenbauer ◽  
Julián Mestre
Keyword(s):  
Approximation Algorithms ◽  
Coloring Problem

scholarly journals Equitable Coloring of Graphs. Recent Theoretical Results and New Practical Algorithms

2016 ◽  
Vol 26 (3) ◽  
pp. 281-295 ◽  
Author(s):  
Hanna Furmańczyk ◽  
Andrzej Jastrzębski ◽  
Marek Kubale
Keyword(s):  
Polynomial Time ◽  
Np Hard ◽  
Coloring Problem ◽  
Equitable Coloring ◽  
Practical Algorithms ◽  
Polynomial Time Algorithms ◽  
Sequencing And Scheduling ◽  
General Graphs ◽  
Theoretical Results

AbstractIn many applications in sequencing and scheduling it is desirable to have an underlaying graph as equitably colored as possible. In this paper we survey recent theoretical results concerning conditions for equitable colorability of some graphs and recent theoretical results concerning the complexity of equitable coloring problem. Next, since the general coloring problem is strongly NP-hard, we report on practical experiments with some efficient polynomial-time algorithms for approximate equitable coloring of general graphs.

scholarly journals Parameterized and Approximation Algorithms for the Load Coloring Problem

Algorithmica ◽  
2016 ◽  
Vol 79 (1) ◽  
pp. 211-229 ◽  
Author(s):  
F. Barbero ◽  
G. Gutin ◽  
M. Jones ◽  
B. Sheng
Keyword(s):  
Approximation Algorithms ◽  
Coloring Problem
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