Add missing parallel=:threads implementations

src/Parallel/distance.jl

@@ -1,20 +1,55 @@
 # used in shortest path calculations
 
 function eccentricity(
+    g::AbstractGraph,
+    vs=vertices(g),
+    distmx::AbstractMatrix{T}=weights(g);
+    parallel::Symbol=:distributed,
+) where {T<:Number}
+    return if parallel === :threads
+        threaded_eccentricity(g, vs, distmx)
+    elseif parallel === :distributed
+        distr_eccentricity(g, vs, distmx)
+    else
+        throw(
+            ArgumentError(
+                "Unsupported parallel argument '$(repr(parallel))' (supported: ':threads' or ':distributed')",
+            ),
+        )
+    end
+end
+
+function distr_eccentricity(
     g::AbstractGraph, vs=vertices(g), distmx::AbstractMatrix{T}=weights(g)
 ) where {T<:Number}
     vlen = length(vs)
     eccs = SharedVector{T}(vlen)
     @sync @distributed for i in 1:vlen
-        eccs[i] = maximum(Graphs.dijkstra_shortest_paths(g, vs[i], distmx).dists)
+        local d = Graphs.dijkstra_shortest_paths(g, vs[i], distmx)
+        eccs[i] = maximum(d.dists)
     end
     d = sdata(eccs)
     maximum(d) == typemax(T) && @warn("Infinite path length detected")
     return d
 end
 
-function eccentricity(g::AbstractGraph, distmx::AbstractMatrix)
-    return eccentricity(g, vertices(g), distmx)
+function threaded_eccentricity(
+    g::AbstractGraph, vs=vertices(g), distmx::AbstractMatrix{T}=weights(g)
+) where {T<:Number}
+    vlen = length(vs)
+    eccs = Vector{T}(undef, vlen)
+    Base.Threads.@threads for i in 1:vlen
+        d = Graphs.dijkstra_shortest_paths(g, vs[i], distmx)
+        eccs[i] = maximum(d.dists)
+    end
+    maximum(eccs) == typemax(T) && @warn("Infinite path length detected")
+    return eccs
+end
+
+function eccentricity(
+    g::AbstractGraph, distmx::AbstractMatrix; parallel::Symbol=:distributed
+)
+    return eccentricity(g, vertices(g), distmx; parallel)
 end
 
 function diameter(g::AbstractGraph, distmx::AbstractMatrix=weights(g))

src/Parallel/shortestpaths/dijkstra.jl

@@ -9,14 +9,54 @@
 end
 
 """
-    Parallel.dijkstra_shortest_paths(g, sources=vertices(g), distmx=weights(g))
+    Parallel.dijkstra_shortest_paths(g, sources=vertices(g), distmx=weights(g), parallel=:distributed)
 
 Compute the shortest paths between all pairs of vertices in graph `g` by running
 [`dijkstra_shortest_paths`] for every vertex and using an optional list of source vertex `sources` and
 an optional distance matrix `distmx`. Return a [`Parallel.MultipleDijkstraState`](@ref) with relevant
-traversal information.
+traversal information. The `parallel` argument can be set to `:threads` or `:distributed` for multi-
+threaded or multi-process parallelism, respectively.
 """
 function dijkstra_shortest_paths(
+    g::AbstractGraph{U},
+    sources=vertices(g),
+    distmx::AbstractMatrix{T}=weights(g);
+    parallel::Symbol=:distributed,
+) where {T<:Number} where {U}
+    return if parallel === :threads
+        threaded_dijkstra_shortest_paths(g, sources, distmx)
+    elseif parallel === :distributed
+        distr_dijkstra_shortest_paths(g, sources, distmx)
+    else
+        throw(
+            ArgumentError(
+                "Unsupported parallel argument '$(repr(parallel))' (supported: ':threads' or ':distributed')",
+            ),
+        )
+    end
+end
+
+function threaded_dijkstra_shortest_paths(
+    g::AbstractGraph{U}, sources=vertices(g), distmx::AbstractMatrix{T}=weights(g)
+) where {T<:Number} where {U}
+    n_v = nv(g)
+    r_v = length(sources)
+
+    # TODO: remove `Int` once julialang/#23029 / #23032 are resolved
+    dists = Matrix{T}(undef, Int(r_v), Int(n_v))
+    parents = Matrix{U}(undef, Int(r_v), Int(n_v))
+
+    Base.Threads.@threads for i in 1:r_v
+        state = Graphs.dijkstra_shortest_paths(g, sources[i], distmx)
+        dists[i, :] = state.dists
+        parents[i, :] = state.parents
+    end
+
+    result = MultipleDijkstraState(dists, parents)
+    return result
+end
+
+function distr_dijkstra_shortest_paths(
     g::AbstractGraph{U}, sources=vertices(g), distmx::AbstractMatrix{T}=weights(g)
 ) where {T<:Number} where {U}
     n_v = nv(g)

src/Parallel/traversals/greedy_color.jl

@@ -1,4 +1,31 @@
-function random_greedy_color(g::AbstractGraph{T}, reps::Integer) where {T<:Integer}
+function random_greedy_color(
+    g::AbstractGraph{T}, reps::Integer; parallel::Symbol=:distributed
+) where {T<:Integer}
+    return if parallel === :threads
+        threaded_random_greedy_color(g, reps)
+    elseif parallel === :distributed
+        distr_random_greedy_color(g, reps)
+    else
+        throw(
+            ArgumentError(
+                "Unsupported parallel argument '$(repr(parallel))' (supported: ':threads' or ':distributed')",
+            ),
+        )
+    end
+end
+
+function threaded_random_greedy_color(g::AbstractGraph{T}, reps::Integer) where {T<:Integer}
+    local_best = Vector{Graphs.Coloring{T}}(undef, reps)
+    Base.Threads.@threads for i in 1:reps
+        seq = shuffle(vertices(g))
+        local_best[i] = Graphs.perm_greedy_color(g, seq)
+    end
+    best = reduce(Graphs.best_color, local_best)
+
+    return convert(Graphs.Coloring{T}, best)
+end
+
+function distr_random_greedy_color(g::AbstractGraph{T}, reps::Integer) where {T<:Integer}
     best = @distributed (Graphs.best_color) for i in 1:reps
         seq = shuffle(vertices(g))
         Graphs.perm_greedy_color(g, seq)
@@ -8,11 +35,14 @@
 end
 
 function greedy_color(
-    g::AbstractGraph{U}; sort_degree::Bool=false, reps::Integer=1
+    g::AbstractGraph{U};
+    sort_degree::Bool=false,
+    reps::Integer=1,
+    parallel::Symbol=:distributed,
 ) where {U<:Integer}
     return if sort_degree
         Graphs.degree_greedy_color(g)
     else
-        Parallel.random_greedy_color(g, reps)
+        Parallel.random_greedy_color(g, reps; parallel)
     end
 end

test/parallel/distance.jl

@@ -1,4 +1,4 @@
-@testset "Parallel.Distance" begin
+@testset "Parallel.Distance" for parallel in [:threads, :distributed]
     g4 = path_digraph(5)
     adjmx1 = [0 1 0; 1 0 1; 0 1 0] # graph
     adjmx2 = [0 1 0; 1 0 1; 1 1 0] # digraph
@@ -9,7 +9,7 @@
 
     for g in testgraphs(a1)
         z = @inferred(Graphs.eccentricity(g, distmx1))
-        y = @inferred(Parallel.eccentricity(g, distmx1))
+        y = @inferred(Parallel.eccentricity(g, distmx1; parallel))
         @test isapprox(y, z)
         @test @inferred(Graphs.diameter(y)) ==
             @inferred(Parallel.diameter(g, distmx1)) ==
@@ -21,9 +21,15 @@
         @test @inferred(Graphs.center(y)) == @inferred(Parallel.center(g, distmx1)) == [2]
     end
 
+    let g = testgraphs(a1)[1]
+        # An error should be reported if the parallel mode could not be understood
+        @test_throws ArgumentError Parallel.eccentricity(g, distmx1; parallel=:thread)
+        @test_throws ArgumentError Parallel.eccentricity(g, distmx1; parallel=:distriibuted)
+    end
+
     for g in testdigraphs(a2)
         z = @inferred(Graphs.eccentricity(g, distmx2))
-        y = @inferred(Parallel.eccentricity(g, distmx2))
+        y = @inferred(Parallel.eccentricity(g, distmx2; parallel))
         @test isapprox(y, z)
         @test @inferred(Graphs.diameter(y)) ==
             @inferred(Parallel.diameter(g, distmx2)) ==

test/parallel/shortestpaths/dijkstra.jl

@@ -1,4 +1,4 @@
-@testset "Parallel.Dijkstra" begin
+@testset "Parallel.Dijkstra" for parallel in [:threads, :distributed]
     g4 = path_digraph(5)
     d1 = float([0 1 2 3 4; 5 0 6 7 8; 9 10 0 11 12; 13 14 15 0 16; 17 18 19 20 0])
     d2 = sparse(float([0 1 2 3 4; 5 0 6 7 8; 9 10 0 11 12; 13 14 15 0 16; 17 18 19 20 0]))
@@ -8,7 +8,7 @@
 
     for g in testgraphs(g3)
         z = floyd_warshall_shortest_paths(g, d)
-        zp = @inferred(Parallel.dijkstra_shortest_paths(g, collect(1:5), d))
+        zp = @inferred(Parallel.dijkstra_shortest_paths(g, collect(1:5), d; parallel))
         @test all(isapprox(z.dists, zp.dists))
 
         for i in 1:5
@@ -21,7 +21,7 @@
         end
 
         z = floyd_warshall_shortest_paths(g)
-        zp = @inferred(Parallel.dijkstra_shortest_paths(g))
+        zp = @inferred(Parallel.dijkstra_shortest_paths(g; parallel))
         @test all(isapprox(z.dists, zp.dists))
 
         for i in 1:5
@@ -34,7 +34,7 @@
         end
 
         z = floyd_warshall_shortest_paths(g)
-        zp = @inferred(Parallel.dijkstra_shortest_paths(g, [1, 2]))
+        zp = @inferred(Parallel.dijkstra_shortest_paths(g, [1, 2]; parallel))
         @test all(isapprox(z.dists[1:2, :], zp.dists))
 
         for i in 1:2
@@ -51,9 +51,17 @@
     g3 = path_digraph(5)
     d = float([0 1 2 3 4; 5 0 6 7 8; 9 10 0 11 12; 13 14 15 0 16; 17 18 19 20 0])
 
+    # An error should be reported if the parallel mode could not be understood
+    @test_throws ArgumentError Parallel.dijkstra_shortest_paths(
+        testdigraphs(g3)[1], collect(1:5), d; parallel=:thread
+    )
+    @test_throws ArgumentError Parallel.dijkstra_shortest_paths(
+        testdigraphs(g3)[1], collect(1:5), d; parallel=:distriibuted
+    )
+
     for g in testdigraphs(g3)
         z = floyd_warshall_shortest_paths(g, d)
-        zp = @inferred(Parallel.dijkstra_shortest_paths(g, collect(1:5), d))
+        zp = @inferred(Parallel.dijkstra_shortest_paths(g, collect(1:5), d; parallel))
         @test all(isapprox(z.dists, zp.dists))
 
         for i in 1:5
@@ -66,7 +74,7 @@
         end
 
         z = floyd_warshall_shortest_paths(g)
-        zp = @inferred(Parallel.dijkstra_shortest_paths(g))
+        zp = @inferred(Parallel.dijkstra_shortest_paths(g; parallel))
         @test all(isapprox(z.dists, zp.dists))
 
         for i in 1:5
@@ -79,7 +87,7 @@
         end
 
         z = floyd_warshall_shortest_paths(g)
-        zp = @inferred(Parallel.dijkstra_shortest_paths(g, [1, 2]))
+        zp = @inferred(Parallel.dijkstra_shortest_paths(g, [1, 2]; parallel))
         @test all(isapprox(z.dists[1:2, :], zp.dists))
 
         for i in 1:2

test/parallel/traversals/greedy_color.jl

@@ -1,19 +1,31 @@
-@testset "Parallel.Greedy Coloring" begin
+@testset "Parallel.Greedy Coloring" for parallel in [:threads, :distributed]
     g3 = star_graph(10)
     for g in testgraphs(g3)
         for op_sort in (true, false)
-            C = @inferred(Parallel.greedy_color(g, reps=5, sort_degree=op_sort))
+            C = @inferred(Parallel.greedy_color(g; reps=5, sort_degree=op_sort, parallel))
             @test C.num_colors == 2
         end
     end
 
     g4 = path_graph(20)
     g5 = complete_graph(20)
 
+    let g = testgraphs(g4)[1]
+        # An error should be reported if the parallel mode could not be understood
+        @test_throws ArgumentError Parallel.greedy_color(
+            g; reps=5, sort_degree=false, parallel=:thread
+        )
+        @test_throws ArgumentError Parallel.greedy_color(
+            g; reps=5, sort_degree=false, parallel=:distriibuted
+        )
+    end
+
     for graph in [g4, g5]
         for g in testgraphs(graph)
             for op_sort in (true, false)
-                C = @inferred(Parallel.greedy_color(g, reps=5, sort_degree=op_sort))
+                C = @inferred(
+                    Parallel.greedy_color(g; reps=5, sort_degree=op_sort, parallel)
+                )
 
                 @test C.num_colors <= maximum(degree(g)) + 1
                 correct = true