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etiennedegetiennedeg
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fix floating point (#3)
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-22
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8 files changed

+68
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‎docs/make.jl‎

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@@ -12,6 +12,7 @@ makedocs(
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"Multiroute flows" => "multiroute.md",
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"Min-cost flows" => "mincost.md",
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"Min-cut" => "mincut.md",
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"Internals" => "internals.md",
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]
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)
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‎docs/src/index.md‎

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@@ -1,4 +1,4 @@
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# GraphsFlows.jl: flow algorithms for Graphs.jl
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# GraphsFlows.jl: flow algorithms for Graphs.jl
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```@meta
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CurrentModule = GraphsFlows
@@ -8,12 +8,6 @@ DocTestSetup = quote
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end
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```
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11-
```@autodocs
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Modules = [GraphsFlows]
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Pages = ["GraphsFlows.jl"]
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Order = [:function, :type]
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```
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1711
This is the documentation page for `GraphsFlows`. In all pages, we assume
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GraphsFlows has been imported into scope and that Graphs.jl has been imported.
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‎docs/src/internals.md‎

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@@ -0,0 +1,8 @@
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# Internals
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```@docs
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GraphsFlows.DefaultCapacity
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GraphsFlows.AbstractFlowAlgorithm
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GraphsFlows.residual
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GraphsFlows.is_zero
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```

‎docs/src/maxflow.md‎

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@@ -1,5 +1,13 @@
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## Max flow algorithms
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```@docs
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maximum_flow
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EdmondsKarpAlgorithm
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DinicAlgorithm
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PushRelabelAlgorithm
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BoykovKolmogorovAlgorithm
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```
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```@autodocs
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Modules = [GraphsFlows]
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Pages = ["maxflow.jl", "boykov_kolmogorov.jl", "push_relabel.jl", "dinic.jl", "edmonds_karp.jl"]

‎src/dinic.jl‎

Lines changed: 13 additions & 8 deletions
Original file line numberDiff line numberDiff line change
@@ -11,17 +11,19 @@ function dinic_impl end
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residual_graph::::Graphs.IsDirected, # the input graph
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source::Integer, # the source vertex
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target::Integer, # the target vertex
14-
capacity_matrix::AbstractMatrix{T} # edge flow capacities
14+
capacity_matrix::AbstractMatrix{T}; # edge flow capacities
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tolerance::T = (T <: AbstractFloat) ? sqrt(eps(T)) : zero(T)
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) where {T}
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n = Graphs.nv(residual_graph) # number of vertexes
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flow_matrix = zeros(T, n, n) # initialize flow matrix
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P = zeros(Int, n) # Sharable parent vector
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2022
flow = 0
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2224
while true
23-
augment = blocking_flow!(residual_graph, source, target, capacity_matrix, flow_matrix, P)
24-
augment == 0 && break
25+
augment = blocking_flow!(residual_graph, source, target, capacity_matrix, flow_matrix, P; tolerance = tolerance)
26+
is_zero(augment; atol = tolerance) && break
2527
flow += augment
2628
end
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return flow, flow_matrix
@@ -42,7 +44,8 @@ function blocking_flow! end
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target::Integer, # the target vertex
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capacity_matrix::AbstractMatrix{T}, # edge flow capacities
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flow_matrix::AbstractMatrix, # the current flow matrix
45-
P::AbstractVector{Int} # Parent vector to store Level Graph
47+
P::AbstractVector{Int}; # Parent vector to store Level Graph
48+
tolerance = (T <: AbstractFloat) ? sqrt(eps(T)) : zero(T)
4649
) where {T}
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n = Graphs.nv(residual_graph) # number of vertexes
4851
fill!(P, -1)
@@ -80,7 +83,7 @@ function blocking_flow! end
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end
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end
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83-
flow == 0 && continue # Flow cannot be augmented along path
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is_zero(flow; atol = tolerance) && continue # Flow cannot be augmented along path
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8588
v = target
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u = bv
@@ -108,11 +111,13 @@ blocking_flow(
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source::Integer, # the source vertex
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target::Integer, # the target vertex
110113
capacity_matrix::AbstractMatrix, # edge flow capacities
111-
flow_matrix::AbstractMatrix, # the current flow matrix
112-
) = blocking_flow!(
114+
flow_matrix::AbstractMatrix{T}; # the current flow matrix
115+
tolerance = (T <: AbstractFloat) ? sqrt(eps(T)) : zero(T)
116+
) where {T}= blocking_flow!(
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residual_graph,
114118
source,
115119
target,
116120
capacity_matrix,
117121
flow_matrix,
118-
zeros(Int, Graphs.nv(residual_graph)))
122+
zeros(Int, Graphs.nv(residual_graph));
123+
tolerance = tolerance)

‎src/maximum_flow.jl‎

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@@ -178,3 +178,11 @@ function maximum_flow(
178178
end
179179
return maximum_flow(flow_graph, source, target, capacity_matrix, algorithm)
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end
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182+
"""
183+
is_zero(value; tolerance)
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185+
Test if the value is equal to zero. It handles floating point errors.
186+
"""
187+
is_zero(value::T; atol = sqrt(eps(T))) where {T<:AbstractFloat} = isapprox(value, zero(T), atol = atol)
188+
is_zero(value; atol) = iszero(value)

‎src/push_relabel.jl‎

Lines changed: 9 additions & 7 deletions
Original file line numberDiff line numberDiff line change
@@ -12,7 +12,8 @@ function push_relabel end
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residual_graph::::Graphs.IsDirected, # the input graph
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source::Integer, # the source vertex
1414
target::Integer, # the target vertex
15-
capacity_matrix::AbstractMatrix{T} # edge flow capacities
15+
capacity_matrix::AbstractMatrix{T}; # edge flow capacities
16+
tolerance::T = (T <: AbstractFloat) ? sqrt(eps(T)) : zero(T)
1617
) where {T}
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1819
n = Graphs.nv(residual_graph)
@@ -43,7 +44,7 @@ function push_relabel end
4344
while length(Q) > 0
4445
v = pop!(Q)
4546
active[v] = false
46-
discharge!(residual_graph, v, capacity_matrix, flow_matrix, excess, height, active, count, Q)
47+
discharge!(residual_graph, v, capacity_matrix, flow_matrix, excess, height, active, count, Q; tolerance = tolerance)
4748
end
4849

4950
return sum([flow_matrix[v, target] for v in Graphs.inneighbors(residual_graph, target)]), flow_matrix
@@ -180,20 +181,21 @@ function discharge! end
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@traitfn function discharge!(
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residual_graph::::Graphs.IsDirected, # the input graph
182183
v::Integer, # vertex to be discharged
183-
capacity_matrix::AbstractMatrix,
184+
capacity_matrix::AbstractMatrix{T},
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flow_matrix::AbstractMatrix,
185186
excess::AbstractVector,
186187
height::AbstractVector{Int},
187188
active::AbstractVector{Bool},
188189
count::AbstractVector{Int},
189-
Q::AbstractVector # FIFO queue
190-
)
190+
Q::AbstractVector; # FIFO queue
191+
tolerance = (T <: AbstractFloat) ? sqrt(eps(T)) : zero(T)
192+
) where {T}
191193
for to in Graphs.outneighbors(residual_graph, v)
192-
excess[v] == 0 && break
194+
is_zero(excess[v]; atol = tolerance) && break
193195
push_flow!(residual_graph, v, to, capacity_matrix, flow_matrix, excess, height, active, Q)
194196
end
195197

196-
if excess[v] > 0
198+
if ! is_zero(excess[v]; atol = tolerance)
197199
if count[height[v] + 1] == 1
198200
gap!(residual_graph, height[v], excess, height, active, count, Q)
199201
else

‎test/push_relabel.jl‎

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@@ -91,4 +91,24 @@
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0 0 0 0 1 0]
9292
g448 = Graphs.DiGraph(M448)
9393
@test maximum_flow(g448, 1, 2, M448, algorithm=PushRelabelAlgorithm())[1] == 1
94+
95+
# Non regression test for floating point error (issue #28 in LightGraphsFlows.jl)
96+
M28 = [0 0 1 1 1 0 0 0
97+
0 0 0 0 0 0 0 0
98+
0 0 0 0 0 1 1 1
99+
0 0 0 0 0 1 1 1
100+
0 0 0 0 0 1 1 1
101+
0 1 0 0 0 0 0 0
102+
0 1 0 0 0 0 0 0
103+
0 1 0 0 0 0 0 0]
104+
g28 = Graphs.DiGraph(M28)
105+
C28 = [0. 0. 0.1 0.1 0.1 0. 0. 0.
106+
0. 0. 0. 0. 0. 0. 0. 0.
107+
0. 0. 0. 0. 0. 1. 1. 1.
108+
0. 0. 0. 0. 0. 1. 1. 1.
109+
0. 0. 0. 0. 0. 1. 1. 1.
110+
0. 0. 0. 0. 0. 0. 0. 0.
111+
0. 0. 0. 0. 0. 0. 0. 0.
112+
0. 0. 0. 0. 0. 0. 0. 0.]
113+
@test maximum_flow(g28, 1, 2, C28, algorithm=PushRelabelAlgorithm())[1] == 0
94114
end

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