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Storing and Accessing Coloring Results

Coloring results in GraphsColoring can be stored in two primary formats:

GroupedColoring (Default)

  • Storage: Colors are stored as a vector of vectors, where each inner vector contains the indices of elements assigned to a specific color.
  • Optimization: Efficient retrieval of all elements belonging to a specific color group.
  • Best for: Operations that frequently access elements by color (e.g., processing color groups in parallel, analyzing group sizes, or visualizing color distributions).
  • Default behavior: This is the default storage format when no storage parameter is specified.

Graphs.Coloring

  • Storage: Colors are stored as a flat vector where colors[i] gives the color assigned to element i.
  • Optimization: Efficient access to the color of a specific element.
  • Best for: Operations that frequently query the color of individual elements.

Usage Examples

Using GroupedColoring (Default)

using PlotlyJS#hide
using CompScienceMeshes#hide
using BEAST#hide
using GraphsColoring#hide

m = meshsphere(1.0, 0.1)#hide
X = raviartthomas(m)#hide

conflicts = GraphsColoring.conflictmatrix(X)#hide

colors = GraphsColoring.color(conflicts; storage=GraphsColoring.GroupedColors())

Using Graphs.Coloring

using PlotlyJS#hide
using CompScienceMeshes#hide
using BEAST#hide
using GraphsColoring#hide

m = meshsphere(1.0, 0.1)#hide
X = raviartthomas(m)#hide

conflicts = GraphsColoring.conflictmatrix(X)#hide

colors = GraphsColoring.color(conflicts; storage=GraphsColoring.GraphsColors())

Accessing Coloring Results

Both storage formats support standard Julia interfaces:

Operation Description
numcolors(c) Returns the total number of distinct colors
eachindex(c) Iterates over color group indices (1-based)
c[i] Retrieves the i-th color group (as a vector of element indices)
length(c[i]) Gets the number of elements in the i-th color group

Example: Accessing Colors

using PlotlyJS#hide
using CompScienceMeshes#hide
using BEAST#hide
using GraphsColoring#hide

m = meshsphere(1.0, 0.1)#hide
X = raviartthomas(m)#hide

conflicts = GraphsColoring.conflictmatrix(X)#hide

colors = GraphsColoring.color(conflicts; algorithm=WorkstreamGreedy, storage=GraphsColoring.GraphsColors()) # hide

println("We have $(numcolors(colors))")
for color in eachindex(colors)
    println("Color $color has $(length(colors[color])) elements. The members of color $color are $(colors[color])")
end

Notes

  • The default storage is GroupedColoring because it enables efficient group-based operations.
  • The Graphs.Coloring format is more efficient for very large problems when only individual element colors are needed.