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Merged
gdalle merged 1 commit into from
May 3, 2025
Merged

Update coloring.jl #251

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59 changes: 34 additions & 25 deletions src/coloring.jl
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Original file line number Diff line number Diff line change
Expand Up @@ -38,8 +38,9 @@ function partial_distance2_coloring!(
for v in vertices_in_order
for w in neighbors(bg, Val(side), v)
for x in neighbors(bg, Val(other_side), w)
if !iszero(color[x])
forbidden_colors[color[x]] = v
color_x = color[x]
if !iszero(color_x)
forbidden_colors[color_x] = v
end
end
end
Expand Down Expand Up @@ -91,9 +92,10 @@ function star_coloring(
for v in vertices_in_order
for (w, index_vw) in neighbors_with_edge_indices(g, v)
!has_diagonal(g) || (v == w && continue)
iszero(color[w]) && continue
forbidden_colors[color[w]] = v
(p, q, _) = first_neighbor[color[w]]
color_w = color[w]
iszero(color_w) && continue
forbidden_colors[color_w] = v
(p, q, _) = first_neighbor[color_w]
if p == v # Case 1
if treated[q] != v
# forbid colors of neighbors of q
Expand All @@ -105,9 +107,10 @@ function star_coloring(
first_neighbor[color[w]] = (v, w, index_vw)
for (x, index_wx) in neighbors_with_edge_indices(g, w)
!has_diagonal(g) || (w == x && continue)
(x == v || iszero(color[x])) && continue
color_x = color[x]
(x == v || iszero(color_x)) && continue
if x == hub[star[index_wx]] # potential Case 2 (which is always false for trivial stars with two vertices, since the associated hub is negative)
forbidden_colors[color[x]] = v
forbidden_colors[color_x] = v
end
end
end
Expand Down Expand Up @@ -141,8 +144,9 @@ function _treat!(
)
for x in neighbors(g, w)
!has_diagonal(g) || (w == x && continue)
iszero(color[x]) && continue
forbidden_colors[color[x]] = v
color_x = color[x]
iszero(color_x) && continue
forbidden_colors[color_x] = v
end
treated[w] = v
return nothing
Expand All @@ -160,7 +164,8 @@ function _update_stars!(
)
for (w, index_vw) in neighbors_with_edge_indices(g, v)
!has_diagonal(g) || (v == w && continue)
iszero(color[w]) && continue
color_w = color[w]
iszero(color_w) && continue
x_exists = false
for (x, index_wx) in neighbors_with_edge_indices(g, w)
!has_diagonal(g) || (w == x && continue)
Expand All @@ -173,7 +178,7 @@ function _update_stars!(
end
end
if !x_exists
(p, q, index_pq) = first_neighbor[color[w]]
(p, q, index_pq) = first_neighbor[color_w]
if p == v && q != w # vw, vq ∈ E and color[w] = color[q]
star_vq = star[index_pq]
hub[star_vq] = v # this may already be true
Expand Down Expand Up @@ -241,22 +246,24 @@ function acyclic_coloring(
for v in vertices_in_order
for w in neighbors(g, v)
!has_diagonal(g) || (v == w && continue)
iszero(color[w]) && continue
forbidden_colors[color[w]] = v
color_w = color[w]
iszero(color_w) && continue
forbidden_colors[color_w] = v
end
for w in neighbors(g, v)
!has_diagonal(g) || (v == w && continue)
iszero(color[w]) && continue
for (x, index_wx) in neighbors_with_edge_indices(g, w)
!has_diagonal(g) || (w == x && continue)
iszero(color[x]) && continue
if forbidden_colors[color[x]] != v
color_x = color[x]
iszero(color_x) && continue
if forbidden_colors[color_x] != v
_prevent_cycle!(
v,
w,
x,
index_wx,
color,
color_x,
first_visit_to_tree,
forbidden_colors,
forest,
Expand All @@ -272,16 +279,18 @@ function acyclic_coloring(
end
for (w, index_vw) in neighbors_with_edge_indices(g, v) # grow two-colored stars around the vertex v
!has_diagonal(g) || (v == w && continue)
iszero(color[w]) && continue
_grow_star!(v, w, index_vw, color, first_neighbor, forest)
color_w = color[w]
iszero(color_w) && continue
_grow_star!(v, w, index_vw, color_w, first_neighbor, forest)
end
for (w, index_vw) in neighbors_with_edge_indices(g, v)
!has_diagonal(g) || (v == w && continue)
iszero(color[w]) && continue
for (x, index_wx) in neighbors_with_edge_indices(g, w)
!has_diagonal(g) || (w == x && continue)
(x == v || iszero(color[x])) && continue
if color[x] == color[v]
color_x = color[x]
(x == v || iszero(color_x)) && continue
if color_x == color[v]
_merge_trees!(v, w, x, index_vw, index_wx, forest) # merge trees T₁ ∋ vw and T₂ ∋ wx if T₁ != T₂
end
end
Expand All @@ -305,7 +314,7 @@ function _prevent_cycle!(
w::Integer,
x::Integer,
index_wx::Integer,
color::AbstractVector{<:Integer},
color_x::Integer,
# modified
first_visit_to_tree::AbstractVector{<:Tuple},
forbidden_colors::AbstractVector{<:Integer},
Expand All @@ -316,7 +325,7 @@ function _prevent_cycle!(
if p != v # T is being visited from vertex v for the first time
first_visit_to_tree[root_wx] = (v, w)
elseif q != w # T is connected to vertex v via at least two edges
forbidden_colors[color[x]] = v
forbidden_colors[color_x] = v
end
return nothing
end
Expand All @@ -326,15 +335,15 @@ function _grow_star!(
v::Integer,
w::Integer,
index_vw::Integer,
color::AbstractVector{<:Integer},
color_w::Integer,
# modified
first_neighbor::AbstractVector{<:Tuple},
forest::Forest{<:Integer},
)
# Create a new tree T_{vw} consisting only of edge vw
(p, q, index_pq) = first_neighbor[color[w]]
(p, q, index_pq) = first_neighbor[color_w]
if p != v # a neighbor of v with color[w] encountered for the first time
first_neighbor[color[w]] = (v, w, index_vw)
first_neighbor[color_w] = (v, w, index_vw)
else # merge T_{vw} with a two-colored star being grown around v
root_vw = find_root!(forest, index_vw)
root_pq = find_root!(forest, index_pq)
Expand Down
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