fix enumerate_paths

see discussion in JuliaAttic#150

doc/source/algorithms.rst

@@ -184,36 +184,59 @@ The user can (optionally) provide a visitor that perform operations along with t
 
     Invoked when a vertex is closed (all its neighbors have been examined).
 
-.. py:function:: enumerate_paths(result[, dest])
+.. py:function:: enumerate_paths(vertices, parent_indices[, dest])
 
-    Returns an array of vectors (containing vertices), whose ``i``-th element corresponds to the path from a source to vertex ``dest[i]``. Empty vectors indicate vertices that are unreachable from the source. ``dest`` can be a subset of vertices, or left unspecified (in which case, all the vertices in the graph will be considered). If ``dest`` is a single vertex, then the result is just an array of vertices, corresponding to the path from a source to ``dest``.
+    Returns an array of vectors (containing vertices), whose ``i``-th element corresponds to the path from a source to vertex ``dest[i]``. Empty vectors indicate vertices that are unreachable from the source. ``dest`` can be a subset of indices, or left unspecified (in which case, all the indices will be considered). If ``dest`` is a single index, then the result is just an array of vertices, corresponding to the path from a source to ``dest``.
 
-    **Remark**: ``enumerate_paths`` is applicable to both ``DijkstraStates`` and ``BellmanFordStates``.
+.. py:function:: enumerate_indices(parent_indices[, dest])
+
+    Returns an array of indices corresponding to the vertices returned by `enumerate_paths(vertices, parent_indices[, dest])`
 
     The following is an example that shows how to use this function:
 
 .. code-block:: python
 
-    julia> using Graphs
-    julia> g3 = simple_graph(4)
-    julia> add_edge!(g3,1,2); add_edge!(g3,1,3); add_edge!(g3,2,3); add_edge!(g3,3,4);
-    julia> s3 = dijkstra_shortest_paths(g3,2)
-    julia> sps = enumerate_paths(s3) # dest: all vertices
+    julia> g4 = Graphs.inclist([4,5,6,7],is_directed=true)
+    julia> add_edge!(g4,4,5); add_edge!(g4,4,6); add_edge!(g4,5,6); add_edge!(g4,6,7)
+    julia> s4 = dijkstra_shortest_paths(g4,5)
+    julia> sps = enumerate_indices(s4.parent_indices) # dest: all indices
     4-element Array{Array{Int64,1},1}:
      []
      [2]
      [2,3]
      [2,3,4]
-    julia> sps = enumerate_paths(s3, [2,4]) # dest: subset of vertices
+
+    julia> enumerate_indices(s4.parent_indices, [2,4]) # dest: subset of indices
     2-element Array{Array{Int64,1},1}:
      [2]
      [2,3,4]
-    julia> sps = enumerate_paths(s3, 4) # dest: single vertex
+
+    julia> enumerate_indices(s4.parent_indices, 4) # dest: single index
     3-element Array{Int64,1}:
      2
      3
      4
 
+    julia> enumerate_paths(vertices(g4), s4.parent_indices) # dest: all vertices
+    4-element Array{Array{Int64,1},1}:
+     []
+     [5]
+     [5,6]
+     [5,6,7]
+
+    julia> enumerate_paths(vertices(g4), s4.parent_indices, [2,4]) # dest: subset of vertices
+    2-element Array{Array{Int64,1},1}:
+     [5]
+     [5,6,7]
+
+    julia> enumerate_paths(vertices(g4), s4.parent_indices, 4) # dest: single vertex
+    3-element Array{Int64,1}:
+     5
+     6
+     7
+
+**Remark**: ``enumerate_paths`` and ``enumerate_indices`` are applicable to the results from both ``dijkstra_shortest_paths`` and ``bellman_ford_shortest_paths``.
+
 Bellman Ford Algorithm
 ~~~~~~~~~~~~~~~~~~~~
 

src/Graphs.jl

@@ -78,7 +78,7 @@ module Graphs
         DijkstraStates, create_dijkstra_states, AbstractDijkstraVisitor,
         dijkstra_shortest_paths!, dijkstra_shortest_paths,
         dijkstra_shortest_paths_withlog,
-        enumerate_paths,
+        enumerate_paths, enumerate_indices,
 
         # bellmanford
         BellmanFordStates, create_bellman_ford_states, NegativeCycleError,

src/bellmanford.jl

@@ -10,7 +10,7 @@ type NegativeCycleError <: Exception end
 
 type BellmanFordStates{V,D<:Number}
     parents::Vector{V}
-    hasparent::Vector{Bool}
+    parent_indices::Vector{Int}
     dists::Vector{D}
 end
 
@@ -19,10 +19,10 @@ end
 function create_bellman_ford_states{V,D<:Number}(g::AbstractGraph{V}, ::Type{D})
     n = num_vertices(g)
     parents = Array(V, n)
-    hasparent = fill(false, n)
+    parent_indices = zeros(Int, n)
     dists = fill(typemax(D), n)
 
-    BellmanFordStates(parents,hasparent, dists)
+    BellmanFordStates(parents, parent_indices, dists)
 end
 
 function bellman_ford_shortest_paths!{V,D}(
@@ -40,6 +40,7 @@ function bellman_ford_shortest_paths!{V,D}(
         i = vertex_index(v, graph)
         state.dists[i] = 0
         state.parents[i] = v
+        state.parent_indices[i] = i
         push!(active, v)
     end
     no_changes = false
@@ -55,7 +56,7 @@ function bellman_ford_shortest_paths!{V,D}(
                 if state.dists[vind] > state.dists[uind] + edist
                     state.dists[vind] = state.dists[uind] + edist
                     state.parents[vind] = u
-                    state.hasparent[vind] = true
+                    state.parent_indices[vind] = vertex_index(u, graph)
                     no_changes = false
                     push!(new_active, v)
                 end
@@ -109,27 +110,3 @@ function has_negative_edge_cycle{V, D}(
     has_negative_edge_cycle(graph, edge_inspector)
 end
 
-function enumerate_paths{V,D<:Number}(state::BellmanFordStates{V,D}, dest::Vector{V})
-    parents = state.parents
-    hasparent = state.hasparent
-
-    num_dest = length(dest)
-    all_paths = Array(Vector{V},num_dest)
-    for i=1:num_dest
-        all_paths[i] = V[]
-        index = dest[i]
-        if hasparent[index] || parents[index] == index
-            while hasparent[index]
-                push!(all_paths[i], index)
-                index = parents[index]
-            end
-            push!(all_paths[i], index)
-            reverse!(all_paths[i])
-        end
-    end
-    all_paths
-end
-
-enumerate_paths{V,D<:Number}(state::BellmanFordStates{V,D}, dest) = enumerate_paths(state, [dest])[1]
-enumerate_paths{V,D<:Number}(state::BellmanFordStates{V,D}) = enumerate_paths(state, [1:length(state.parents)])
-

src/dijkstra_spath.jl

@@ -8,7 +8,7 @@
 
 type DijkstraStates{V,D<:Number,Heap,H}
     parents::Vector{V}
-    hasparent::Vector{Bool}
+    parent_indices::Vector{Int}
     dists::Vector{D}
     colormap::Vector{Int}
     heap::Heap
@@ -27,13 +27,13 @@ end
 function create_dijkstra_states{V,D<:Number}(g::AbstractGraph{V}, ::Type{D})
     n = num_vertices(g)
     parents = Array(V, n)
-    hasparent = fill(false, n)
+    parent_indices = zeros(Int, n)
     dists = fill(typemax(D), n)
     colormap = zeros(Int, n)
     heap = mutable_binary_minheap(DijkstraHEntry{V,D})
     hmap = zeros(Int, n)
 
-    DijkstraStates(parents, hasparent, dists, colormap, heap, hmap)
+    DijkstraStates(parents, parent_indices, dists, colormap, heap, hmap)
 end
 
 ###################################################################
@@ -98,7 +98,7 @@ end
 function set_source!{V,D}(state::DijkstraStates{V,D}, g::AbstractGraph{V}, s::V)
     i = vertex_index(s, g)
     state.parents[i] = s
-    state.hasparent[i] = false
+    state.parent_indices[i] = i
     state.dists[i] = 0
     state.colormap[i] = 2
 end
@@ -111,7 +111,7 @@ function process_neighbors!{V,D,Heap,H}(
 
     dists::Vector{D} = state.dists
     parents::Vector{V} = state.parents
-    hasparent::Vector{Bool} = state.hasparent
+    parent_indices::Vector{Int} = state.parent_indices
     colormap::Vector{Int} = state.colormap
     heap::Heap = state.heap
     hmap::Vector{H} = state.hmap
@@ -125,7 +125,7 @@ function process_neighbors!{V,D,Heap,H}(
         if v_color == 0
             dists[iv] = dv = du + edge_property(edge_dists, e, graph)
             parents[iv] = u
-            hasparent[iv] = true
+            parent_indices[iv] = vertex_index(u, graph)
             colormap[iv] = 1
             discover_vertex!(visitor, u, v, dv)
 
@@ -137,7 +137,7 @@ function process_neighbors!{V,D,Heap,H}(
             if dv < dists[iv]
                 dists[iv] = dv
                 parents[iv] = u
-                hasparent[iv] = true
+                parent_indices[iv] = vertex_index(u, graph)
 
                 # update the value on the heap
                 update_vertex!(visitor, u, v, dv)
@@ -254,19 +254,16 @@ dijkstra_shortest_paths{V}(
     graph::AbstractGraph{V}, s::V
 ) = dijkstra_shortest_paths(graph, ones(num_vertices(graph)), s)
 
-function enumerate_paths{V,D,Heap,H}(state::DijkstraStates{V,D,Heap,H}, dest::Vector{V})
-    parents = state.parents
-    hasparent = state.hasparent
-
-    num_dest = length(dest)
-    all_paths = Array(Vector{V},num_dest)
+function enumerate_indices(parent_indices::Vector{Int}, dest_indices::Vector{Int})
+    num_dest = length(dest_indices)
+    all_paths = Array(Vector{Int},num_dest)
     for i=1:num_dest
-        all_paths[i] = V[]
-        index = dest[i]
-        if hasparent[index] || parents[index] == index
-            while hasparent[index]
+        all_paths[i] = Int[]
+        index = dest_indices[i]
+        if parent_indices[index] != 0
+            while parent_indices[index] != index
                 push!(all_paths[i], index)
-                index = parents[index]
+                index = parent_indices[index]
             end
             push!(all_paths[i], index)
             reverse!(all_paths[i])
@@ -275,5 +272,8 @@ function enumerate_paths{V,D,Heap,H}(state::DijkstraStates{V,D,Heap,H}, dest::Ve
     all_paths
 end
 
-enumerate_paths{V,D,Heap,H}(state::DijkstraStates{V,D,Heap,H}, dest::V) = enumerate_paths(state, V[dest])[1]
-enumerate_paths{V,D,Heap,H}(state::DijkstraStates{V,D,Heap,H}) = enumerate_paths(state, [1:length(state.parents)])
+enumerate_indices(parent_indices::Vector{Int}, dest_index::Int) = enumerate_indices(parent_indices, Int[dest_index])[1]
+enumerate_indices(parent_indices::Vector{Int}) = enumerate_indices(parent_indices, [1:length(parent_indices)])
+enumerate_paths(vertices, parent_indices::Vector{Int}, dest_indices::Vector{Int}) = [vertices[i] for i in enumerate_indices(parent_indices, dest_indices)]
+enumerate_paths(vertices, parent_indices::Vector{Int}, dest_index::Int) = enumerate_paths(vertices, parent_indices, [dest_index])[1]
+enumerate_paths(vertices, parent_indices::Vector{Int}) = enumerate_paths(vertices, parent_indices, [1:length(parent_indices)])

test/bellman_test.jl

@@ -35,10 +35,9 @@ s1 = bellman_ford_shortest_paths(g1, eweights1, [1])
 
 @test s1.parents == [1, 3, 1, 2, 3]
 @test s1.dists == [0., 8., 5., 9., 7.]
-@test s1.hasparent == [false, true, true, true, true]
 
 ## all destinations
-sps = enumerate_paths(s1)
+sps = enumerate_paths(vertices(g1), s1.parent_indices)
 @test length(sps) == 5
 @test sps[1] == [1]
 @test sps[2] == [1,3,2]
@@ -47,24 +46,23 @@ sps = enumerate_paths(s1)
 @test sps[5] == [1,3,5]
 
 ## multiple destinations
-sps = enumerate_paths(s1, [2,4])
+sps = enumerate_paths(vertices(g1), s1.parent_indices, [2,4])
 @test length(sps) == 2
 @test sps[1] == [1,3,2]
 @test sps[2] == [1,3,2,4]
 
 ## single destination
-sps = enumerate_paths(s1, 2)
+sps = enumerate_paths(vertices(g1), s1.parent_indices, 2)
 @test sps == [1,3,2]
-@test sps == enumerate_paths(s1, [2])[1]
+@test sps == enumerate_paths(vertices(g1), s1.parent_indices, [2])[1]
 
 # Multiple Sources
 
 s1 = bellman_ford_shortest_paths(g1, eweights1, [1, 2])
 @test s1.parents == [1, 2, 2, 2, 3]
 @test s1.dists == [0., 0., 2., 1., 4.]
-@test s1.hasparent == [false, false, true, true, true]
 
-sps = enumerate_paths(s1)
+sps = enumerate_paths(vertices(g1), s1.parent_indices)
 @test sps[1] == [1]
 @test sps[2] == [2]
 @test sps[3] == [2,3]

test/dijkstra.jl

@@ -115,17 +115,51 @@ g3 = simple_graph(4)
 add_edge!(g3,1,2); add_edge!(g3,1,3); add_edge!(g3,2,3); add_edge!(g3,3,4)
 
 s3 = dijkstra_shortest_paths(g3,2)
-sps = enumerate_paths(s3)
+sps = enumerate_paths(vertices(g3), s3.parent_indices)
 @test length(sps) == 4
 @test sps[1] == []
 @test sps[2] == [2]
 @test sps[3] == [2, 3]
 @test sps[4] == [2, 3, 4]
 
-sps = enumerate_paths(s3, [2,4])
+sps = enumerate_paths(vertices(g3), s3.parent_indices, [2,4])
 @test length(sps) == 2
 @test sps[1] == [2]
 @test sps[2] == [2, 3, 4]
 
-sps = enumerate_paths(s3, 4)
-@test sps == [2, 3, 4]
+sps = enumerate_paths(vertices(g3), s3.parent_indices, 4)
+@test sps == [2, 3, 4]
+
+g4 = Graphs.inclist([4,5,6,7],is_directed=true)
+add_edge!(g4,4,5); add_edge!(g4,4,6); add_edge!(g4,5,6); add_edge!(g4,6,7)
+
+s4 = dijkstra_shortest_paths(g4,5)
+sps = enumerate_indices(s4.parent_indices)
+@test length(sps) == 4
+@test sps[1] == []
+@test sps[2] == [2]
+@test sps[3] == [2, 3]
+@test sps[4] == [2, 3, 4]
+
+sps = enumerate_indices(s4.parent_indices, [2,4])
+@test length(sps) == 2
+@test sps[1] == [2]
+@test sps[2] == [2, 3, 4]
+
+sps = enumerate_indices(s4.parent_indices, 4)
+@test sps == [2, 3, 4]
+
+sps = enumerate_paths(vertices(g4), s4.parent_indices)
+@test length(sps) == 4
+@test sps[1] == []
+@test sps[2] == [5]
+@test sps[3] == [5, 6]
+@test sps[4] == [5, 6, 7]
+
+sps = enumerate_paths(vertices(g4), s4.parent_indices, [2,4])
+@test length(sps) == 2
+@test sps[1] == [5]
+@test sps[2] == [5, 6, 7]
+
+sps = enumerate_paths(vertices(g4), s4.parent_indices, 4)
+@test sps == [5, 6, 7]