B-coloring is a theoretical optimization problem on graph that, top of being used to model some real-world applications, exploited by bounding techniques embedded into solvers for the classical coloring problem. This implies that improved solutions b-coloring have an impact even larger pool practical applications modelled in several different fields such as scheduling, timetabling and telecommu...

A new variation of the coloring problem, μ-coloring, is defined in this paper. Given a graph G and a function μ, a μ-coloring is a coloring where each vertex v of G must receive a color at most μ(v). It is proved that μ-coloring lies between coloring and list-coloring, in the sense of generalization of problems and computational complexity. The notion of perfection is extended for μ-coloring, l...

Consider the coloring of a vertex-labelled r-uniform hypergraph G(V,E), where V is the vertex set of n labelled vertices, and E is the set of hyperedges. In case of proper bicoloring, given two colors, we need to assign each vertex with one of the colors so that none of the hyperedges is monochromatic. This may not always be possible. In such cases, we use multiple bicolorings to ensure that ea...

Given an n-vertex graph G, an edge-coloring of G with natural numbers is a consecutive (or interval) coloring if the colors of edges incident with each vertex are distinct and form an interval of integers. In this paper we prove that if G has a consecutive coloring and n¿3 then S(G)62n − 4, where S(G) is the maximum number of colors allowing a consecutive coloring. Next, we investigate the so-c...

A proper edge t-coloring of a graphG is a coloring of edges of G with colors 1, 2, . . . , t such that all colors are used, and no two adjacent edges receive the same color. The set of colors of edges incident with a vertex x is called a spectrum of x. Any nonempty subset of consecutive integers is called an interval. A proper edge t-coloring of a graph G is interval in the vertex x if the spec...

A b-coloring is a proper coloring of the vertices of a graph such that each color class has a vertex that has neighbors of all other colors. The b-chromatic number of a graph G is the largest k such that G admits a b-coloring with k colors. A graph G is b-critical if the removal of any vertex of G decreases the b-chromatic number. We prove various properties of b-critical trees. In particular, ...

Let G be a simple graph. A total coloring f of G is called E-total-coloring if no two adjacent vertices of G receive the same color and no edge of G receives the same color as one of its endpoints. For E-total-coloring f of a graph G and any vertex u of G, let Cf (u) or C(u) denote the set of colors of vertex u and the edges incident to u. We call C(u) the color set of u. If C(u) 6= C(v) for an...

We present new multithreaded vertex ordering and distance-k graph coloring algorithms that are well-suited for multicore platforms. The vertex ordering techniques rely on various notions of “degree”, are known to be effective in reducing the number of colors used by a greedy coloring algorithm, and are generic enough to be applicable to contexts other than coloring. We employ approximate degree...

A k?coloring of an oriented graph G = (V; A) is an assignment c of one of the colors 1; 2; : : :; k to each vertex of the graph such that, for every arc (x; y) of G, c(x) 6 = c(y). The k?coloring is good if for every arc (x; y) of G there is no arc (z; t) 2 A such that c(x) = c(t) and c(y) = c(z). A k?coloring is said to be semi?strong if for every vertex x of G, c(z) 6 = c(t) for any pair fz; ...

In an ordinary edge-coloring of a graph each color appears at each vertex at most once. An f -coloring is a generalized edge-coloring in which each color appears at each vertex v at most f(v) times where f(v) is a positive integer assigned to v. This paper gives efficient sequential and parallel algorithms to find ordinary edge-colorings and f -colorings for various classes of graphs such as bi...