This Festschrift is in honor of Ker-I Ko, Professor in the Stony Brook University, USA. He contributed significantly to advancing the theory of structural complexity, especially on polynomial-time isomorphism, instance complexity, and relativization of polynomial-time hierarchy.

In Memoriam: Ker-I Ko (1950-2018).- Ker-I Ko and the Study of Resource-Bounded Kolmogorov Complexity.- The Power of Self-Reducibility Selectivity, Information, and Approximation.- Who Asked Us - How the Theory of Computing Answers, QuestionsAbout Analysis.- Promise Problems on Probability Distributions.- On Nonadaptive Reductions to the Set of Random Strings and its Dense Subsets.- Computability of the Solutions to Navier-Stokes Equations via Recursive Approximation.- Automatic Generation of Structured Overviews over a Very Large Corpus of Documents.- Better Upper Bounds for Searching on a Line with Byzantine Robots.- A Survey on Double Greedy Algorithms for Maximizing Non-monotone Submodular Functions.- Sequential Location Game on Continuous Directional Star Networks.- Core Decomposition, Maintenance and Applications.- Active and Busy Time Scheduling Problem: a Survey.- A Note on the Position Value for Hypergraph Communication Situations.- An Efficient Approximation Algorithm for the Steiner Tree Problem.- A Review for Submodular Optimization on Machine Scheduling Problems.- Edge Computing Integrated with Blockchain Technologies.

This Festschrift is in honor of Ker-I Ko, Professor in the Stony Brook University, USA. Ker-I Ko was one of the founding fathers of computational complexity over real numbers and analysis. He and Harvey Friedman devised a theoretical model for real number computations by extending the computation of Turing machines. He contributed significantly to advancing the theory of structural complexity, especially on polynomial-time isomorphism, instance complexity, and relativization of polynomial-time hierarchy. Ker-I also made many contributions to approximation algorithm theory of combinatorial optimization problems. This volume contains 17 contributions in the area of complexity and approximation. Those articles are authored by researchers over the world, including North America, Europe and Asia. Most of them are co-authors, colleagues, friends, and students of Ker-I Ko.

This Festschrift is in honor of Ker-I Ko, who was one of the founding fathers of computational complexity over real numbers and analysis Professor Ker-I Ko was one of the key players in the areas of Computational Complexity Theory, Complexity Theory of Real Functions, and Combinatorial Optimization This volume contains 17 contributions in the area of complexity and approximation, authored by co-authors, colleagues, friends, and students of Ker-I Ko