Fix same-weight bug (issue #5) (#6)

* fix same-weight bug (issue #5) * Fix weight * Fix typos * change to first strategy * revert to spaces * correct formatting using blue style --------- Co-authored-by: etienneINSA <[email protected]>
JuliaGraphs · May 2, 2024 · 76286e2 · 76286e2
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commit 76286e2
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Showing 2 changed files with 36 additions and 16 deletions.
diff --git a/src/blossomv.jl b/src/blossomv.jl
@@ -1,6 +1,6 @@
 """
-    minimum_weight_perfect_matching(g, w::Dict{Edge,Real})
-    minimum_weight_perfect_matching(g, w::Dict{Edge,Real}, cutoff)
+minimum_weight_perfect_matching(g, w::Dict{Edge,Real})
+minimum_weight_perfect_matching(g, w::Dict{Edge,Real}, cutoff)
 
 Given a graph `g` and an edgemap `w` containing weights associated to edges,
 returns a matching with the mimimum total weight among the ones containing
@@ -20,8 +20,10 @@ In case of error try to change the optional argument `tmaxscale` (default is `tm
 """
 function minimum_weight_perfect_matching end
 
-function minimum_weight_perfect_matching(g::Graph, w::Dict{E,U}, cutoff, kws...) where {U<:Real, E<:Edge}
-    wnew = Dict{E, U}()
+function minimum_weight_perfect_matching(
+    g::Graph, w::Dict{E,U}, cutoff, kws...
+) where {U<:Real,E<:Edge}
+    wnew = Dict{E,U}()
     for (e, c) in w
         if c <= cutoff
             wnew[e] = c
@@ -30,40 +32,43 @@ function minimum_weight_perfect_matching(g::Graph, w::Dict{E,U}, cutoff, kws...)
     return minimum_weight_perfect_matching(g, wnew; kws...)
 end
 
-function minimum_weight_perfect_matching(g::Graph, w::Dict{E,U}; tmaxscale=10.) where {U<:AbstractFloat, E<:Edge}
-    wnew = Dict{E, Int32}()
+function minimum_weight_perfect_matching(
+    g::Graph, w::Dict{E,U}; tmaxscale=10.0
+) where {U<:AbstractFloat,E<:Edge}
+    wnew = Dict{E,Int32}()
     cmax = maximum(values(w))
     cmin = minimum(values(w))
-    tmax = typemax(Int32)  / tmaxscale # /10 is kinda arbitrary,
-                                # hopefully high enough to not occur in overflow problems
+
+    tmax = typemax(Int32) / tmaxscale # /10 is kinda arbitrary,
+    # hopefully high enough to not occur in overflow problems
     for (e, c) in w
-        wnew[e] = round(Int32, (c-cmin) / (cmax-cmin) * tmax)
+        wnew[e] = round(Int32, (c - cmin) / max(cmax - cmin, 1) * tmax)
     end
     match = minimum_weight_perfect_matching(g, wnew)
     weight = zero(U)
-    for i=1:nv(g)
+    for i in 1:nv(g)
         j = match.mate[i]
         if j > i
-            weight += w[E(i,j)]
+            weight += w[E(i, j)]
         end
     end
     return MatchingResult(weight, match.mate)
 end
 
-function minimum_weight_perfect_matching(g::Graph, w::Dict{E,U}) where {U<:Integer, E<:Edge}
+function minimum_weight_perfect_matching(g::Graph, w::Dict{E,U}) where {U<:Integer,E<:Edge}
     m = BlossomV.Matching(nv(g))
     for (e, c) in w
-        BlossomV.add_edge(m, src(e)-1, dst(e)-1, c)
+        BlossomV.add_edge(m, src(e) - 1, dst(e) - 1, c)
     end
     BlossomV.solve(m)
 
     mate = fill(-1, nv(g))
     totweight = zero(U)
-    for i=1:nv(g)
-        j = BlossomV.get_match(m, i-1) + 1
+    for i in 1:nv(g)
+        j = BlossomV.get_match(m, i - 1) + 1
         mate[i] = j <= 0 ? -1 : j
         if i < j
-            totweight += w[Edge(i,j)]
+            totweight += w[Edge(i, j)]
         end
     end
     return MatchingResult(totweight, mate)

diff --git a/test/runtests.jl b/test/runtests.jl
@@ -254,6 +254,21 @@ end
     @test match.mate[2] == 3
     @test match.mate[3] == 2
     @test match.weight ≈ 11.5
+
+    # Issue #5
+    g = Graph(Graph([Edge(1,2), Edge(2,3), Edge(4,1)]))
+    w = Dict(Edge(1,2) => 2.0, Edge(2,3) => 2.0, Edge(1,4) => 2.0)
+    match = minimum_weight_perfect_matching(g, w)
+    @test match.mate == [4,3,2,1]
+    @test match.weight == 4.0
+
+    g = Graph([Edge(1,2)])
+    wFloat = Dict(Edge(1,2) => 2.0)
+    wInt = Dict(Edge(1,2) => 2)
+    matchFloat = minimum_weight_perfect_matching(g, wFloat)
+    matchInt = minimum_weight_perfect_matching(g, wInt)
+    @test matchFloat.mate == matchInt.mate
+    @test matchFloat.weight == matchInt.weight
 end