Fix pagerank transpose bug and tests (#44)

Author: gdalle

src/overrides.jl

@@ -55,12 +55,10 @@ Apply the page rank algorithm on a weighted graph.
 """
 function Graphs.pagerank(g::SimpleWeightedDiGraph, α=0.85, n::Integer=100, ϵ=1.0e-6)
     A = weights(g)
-    S = vec(sum(A; dims=1))
-    S = 1 ./ S
+    S = 1 ./ vec(sum(A; dims=2))  # inverse of outdegree
     S[findall(S .== Inf)] .= 0.0
-    M = A'  # need a separate line due to bug #17456 in julia
     # scaling the adjmat to stochastic adjacency matrix
-    M = (Diagonal(S) * M)'
+    M = (Diagonal(S) * A)'
     N = Int(nv(g))
     # solution vector
     x = fill(1.0 / N, N)

test/overrides.jl

@@ -76,7 +76,7 @@
         @test adjacency_matrix(g; dir=:out) == adjacency_matrix(g; dir=:in)'
         @test !issymmetric(laplacian_matrix(g; dir=:out))
         @test laplacian_matrix(g, Float64; dir=:out) ≈ g5_l
-        @test @inferred(pagerank(g))[3] ≈ 0.2266 atol = 0.001
+        @test @inferred(pagerank(g)) ≈ [0.119, 0.186, 0.311, 0.383] atol = 0.001  # checked with networkx
         @test length(@inferred(pagerank(g))) == nv(g)
         @test_throws ErrorException pagerank(g, 2)
         @test_throws ErrorException pagerank(g, 0.85, 2)
@@ -85,4 +85,11 @@
         @test g[2:3] == SimpleWeightedDiGraph{eltype(g5),weighttype(g5)}(gc)
         @test weights(g[2:3])[1, 2] == 2
     end
+
+    let
+        A = [0 1 1; 1 0 0; 0 1 0]
+        g = SimpleDiGraph(A)
+        gw = SimpleWeightedDiGraph(A)
+        @test pagerank(g) ≈ pagerank(gw)
+    end
 end