New extension: ProblemReductionsExt (#50)

* update

* port to ProblemReductions.jl, tests all pass

* port ProblemReductions

* make problemreductions an extension

* fix tests

Project.toml

@@ -7,9 +7,16 @@ version = "0.4.0"
 Graphs = "86223c79-3864-5bf0-83f7-82e725a168b6"
 LuxorGraphPlot = "1f49bdf2-22a7-4bc4-978b-948dc219fbbc"
 
+[weakdeps]
+ProblemReductions = "899c297d-f7d2-4ebf-8815-a35996def416"
+
+[extensions]
+ProblemReductionsExt = "ProblemReductions"
+
 [compat]
 Graphs = "1.6"
 LuxorGraphPlot = "0.5"
+ProblemReductions = "0.1.1"
 julia = "1"
 
 [extras]
@@ -19,4 +26,4 @@ Random = "9a3f8284-a2c9-5f02-9a11-845980a1fd5c"
 Test = "8dfed614-e22c-5e08-85e1-65c5234f0b40"
 
 [targets]
-test = ["Test", "Random", "GenericTensorNetworks", "LinearAlgebra"]
+test = ["Test", "Random", "GenericTensorNetworks", "LinearAlgebra", "ProblemReductions"]

ext/ProblemReductionsExt.jl

@@ -0,0 +1,118 @@
+module ProblemReductionsExt
+
+using UnitDiskMapping, UnitDiskMapping.Graphs
+import ProblemReductions: reduceto, target_problem, extract_multiple_solutions
+import ProblemReductions
+
+function _to_gridgraph(g::UnitDiskMapping.GridGraph)
+    return ProblemReductions.GridGraph(getfield.(g.nodes, :loc), g.radius)
+end
+function _extract_weights(g::UnitDiskMapping.GridGraph{<:WeightedNode})
+    getfield.(g.nodes, :weight)
+end
+
+###### unweighted reduction
+struct IndependentSetToKSG{NT, VT} <: ProblemReductions.AbstractReductionResult
+    mapres::MappingResult{NT}
+    weights::VT
+end
+function ProblemReductions.reduceto(::Type{ProblemReductions.IndependentSet{ProblemReductions.GridGraph{2}, Int, ProblemReductions.UnitWeight}}, problem::ProblemReductions.IndependentSet{GT, Int, ProblemReductions.UnitWeight} where GT<:SimpleGraph)
+    return IndependentSetToKSG(map_graph(UnWeighted(), problem.graph), problem.weights)
+end
+
+function ProblemReductions.target_problem(res::IndependentSetToKSG{<:UnWeightedNode})
+    return ProblemReductions.IndependentSet(_to_gridgraph(res.mapres.grid_graph))
+end
+function ProblemReductions.extract_solution(res::IndependentSetToKSG, sol)
+    return map_config_back(res.mapres, sol)
+end
+
+###### Weighted reduction
+# TODO: rescale the weights to avoid errors
+function ProblemReductions.reduceto(::Type{ProblemReductions.IndependentSet{ProblemReductions.GridGraph{2}, Float64, Vector{Float64}}}, problem::ProblemReductions.IndependentSet{GT} where GT<:SimpleGraph)
+    return IndependentSetToKSG(map_graph(Weighted(), problem.graph), problem.weights)
+end
+function ProblemReductions.target_problem(res::IndependentSetToKSG{<:WeightedNode})
+    graph = _to_gridgraph(res.mapres.grid_graph)
+    weights = UnitDiskMapping.map_weights(res.mapres, res.weights)
+    return ProblemReductions.IndependentSet(graph, weights)
+end
+
+###### Factoring ######
+struct FactoringToIndependentSet{NT} <: ProblemReductions.AbstractReductionResult
+    mapres::FactoringResult{NT}
+    raw_graph::ProblemReductions.GridGraph{2}
+    raw_weight::Vector{Int}
+    vmap::Vector{Int}
+    problem::ProblemReductions.IndependentSet{ProblemReductions.GridGraph{2}, Int, Vector{Int}}
+end
+function ProblemReductions.reduceto(::Type{ProblemReductions.IndependentSet{ProblemReductions.GridGraph{2}, Int, Vector{Int}}}, problem::ProblemReductions.Factoring)
+    mres = map_factoring(problem.m, problem.n)
+    g = _to_gridgraph(mres.grid_graph)
+    ws = getfield.(mres.grid_graph.nodes, :weight)
+    mg, vmap = UnitDiskMapping.set_target(g, [mres.pins_zeros..., mres.pins_output...], problem.input << length(mres.pins_zeros))
+    return FactoringToIndependentSet(mres, g, ws, vmap, ProblemReductions.IndependentSet(mg, ws[vmap]))
+end
+
+function ProblemReductions.target_problem(res::FactoringToIndependentSet)
+    return res.problem
+end
+
+function ProblemReductions.extract_solution(res::FactoringToIndependentSet, sol)
+    cfg = zeros(Int, nv(res.raw_graph))
+    cfg[res.vmap] .= sol
+    i1, i2 = map_config_back(res.mapres, cfg)
+    return vcat([i1>>(k-1) & 1 for k=1:length(res.mapres.pins_input1)], [i2>>(k-1) & 1 for k=1:length(res.mapres.pins_input2)])
+end
+
+###### Spinglass problem to MIS on KSG ######
+# NOTE: I am not sure about the correctness of this reduction. If you encounter a bug, please question this function!
+struct SpinGlassToIndependentSet{NT} <: ProblemReductions.AbstractReductionResult
+    mapres::QUBOResult{NT}
+end
+function ProblemReductions.reduceto(::Type{ProblemReductions.IndependentSet{ProblemReductions.GridGraph{2}, Float64, Vector{Float64}}}, problem::ProblemReductions.SpinGlass{<:SimpleGraph})
+    n = length(problem.h)
+    M = similar(problem.h, n, n)
+    for (e, j) in zip(edges(problem.graph), problem.J)
+        M[e.src, e.dst] = M[e.dst, e.src] = j
+    end
+    return SpinGlassToIndependentSet(map_qubo(M, -problem.h))
+end
+
+function ProblemReductions.target_problem(res::SpinGlassToIndependentSet)
+    grid = _to_gridgraph(res.mapres.grid_graph)
+    ws = getfield.(res.mapres.grid_graph.nodes, :weight)
+    return ProblemReductions.IndependentSet(grid, ws)
+end
+
+function ProblemReductions.extract_solution(res::SpinGlassToIndependentSet, sol)
+    res = map_config_back(res.mapres, sol)
+    return 1 .- 2 .* Int.(res)
+end
+
+###### Spinglass problem on grid to MIS on KSG ######
+# NOTE: the restricted layout is not implemented, since it is not often used
+struct SquareSpinGlassToIndependentSet{NT} <: ProblemReductions.AbstractReductionResult
+    mapres::SquareQUBOResult{NT}
+end
+function ProblemReductions.reduceto(::Type{ProblemReductions.IndependentSet{ProblemReductions.GridGraph{2}, Float64, Vector{Float64}}}, problem::ProblemReductions.SpinGlass{ProblemReductions.GridGraph{2}})
+    g = problem.graph
+    @assert 1 <= g.radius < sqrt(2) "Only support nearest neighbor interaction"
+    coupling = [(g.locations[e.src]..., g.locations[e.dst]..., J) for (e, J) in zip(edges(g), problem.J)]
+    onsite = [(i, j, -h) for ((i, j), h) in zip(g.locations, problem.h)]
+    # a vector coupling of `(i, j, i', j', J)`, s.t. (i', j') == (i, j+1) or (i', j') = (i+1, j).
+    # a vector of onsite term `(i, j, h)`.
+    return SquareSpinGlassToIndependentSet(map_qubo_square(coupling, onsite))
+end
+
+function ProblemReductions.target_problem(res::SquareSpinGlassToIndependentSet)
+    grid = _to_gridgraph(res.mapres.grid_graph)
+    ws = getfield.(res.mapres.grid_graph.nodes, :weight)
+    return ProblemReductions.IndependentSet(grid, ws)
+end
+
+function ProblemReductions.extract_solution(res::SquareSpinGlassToIndependentSet, sol)
+    res = map_config_back(res.mapres, sol)
+    return 1 .- 2 .* Int.(res)
+end
+end 

src/Core.jl

@@ -76,6 +76,12 @@ function Graphs.SimpleGraph(grid::GridGraph{Node{ONE}})
     return unit_disk_graph(getfield.(grid.nodes, :loc), grid.radius)
 end
 coordinates(grid::GridGraph) = getfield.(grid.nodes, :loc)
+function Graphs.neighbors(g::GridGraph, i::Int)
+    [j for j in 1:nv(g) if i != j && distance(g.nodes[i], g.nodes[j]) <= g.radius]
+end
+distance(n1::Node, n2::Node) = sqrt(sum(abs2, n1.loc .- n2.loc))
+Graphs.nv(g::GridGraph) = length(g.nodes)
+Graphs.vertices(g::GridGraph) = 1:nv(g)
 
 # printing function for Grid graphs
 function print_grid(io::IO, grid::GridGraph{Node{WT}}; show_weight=false) where WT

src/multiplier.jl

@@ -97,7 +97,7 @@ function map_factoring(M::Int, N::Int)
         [pinloc(1, j, 1) for j=1:N]...,
         [pinloc(i, N, 4) for i=1:M]...,
     ]
-    return FactoringResult(gg, pp, pq, pm, p0)
+    return FactoringResult(gg, pq, pp, pm, p0)
 end
 
 struct FactoringResult{NT}
@@ -131,7 +131,7 @@ function solve_factoring(missolver, mres::FactoringResult, target::Int)
     return map_config_back(mres, cfg)
 end
 
-function set_target(g::SimpleGraph, pins::AbstractVector, target::Int)
+function set_target(g, pins::AbstractVector, target::Int)
     vs = collect(vertices(g))
     for (i, p) in enumerate(pins)
         bitval = (target >> (i-1)) & 1

test/Core.jl

@@ -0,0 +1,15 @@
+using Test, UnitDiskMapping, Graphs
+
+@testset "GridGraph" begin
+    grid = GridGraph((5, 5), [Node(2, 3), Node(2, 4), Node(5, 5)], 1.2)
+    g = SimpleGraph(grid)
+    @test ne(g) == 1
+    @test vertices(grid) == vertices(g)
+    @test neighbors(grid, 2) == neighbors(g, 2)
+
+    grid = GridGraph((5, 5), [Node(2, 3), Node(2, 4), Node(5, 5)], 4.0)
+    g = SimpleGraph(grid)
+    @test ne(g) == 3
+    @test vertices(grid) == vertices(g)
+    @test neighbors(grid, 2) == neighbors(g, 2)
+end

test/reduceto.jl

@@ -0,0 +1,46 @@
+using Test, UnitDiskMapping, Graphs, GenericTensorNetworks
+import ProblemReductions
+
+@testset "reduction graph" begin
+    @test ProblemReductions.reduction_graph() isa ProblemReductions.ReductionGraph
+end
+
+@testset "rules" begin
+    graph = complete_graph(3)  # triangle
+    fact = ProblemReductions.Factoring(2, 1, 2)
+    is = ProblemReductions.IndependentSet(graph)
+    wis = ProblemReductions.IndependentSet(graph, rand(nv(graph)) .* 0.2)
+    sg = ProblemReductions.SpinGlass(graph, [0.2, 0.4, -0.6], [0.1, 0.1, 0.1])
+    sg2 = ProblemReductions.SpinGlass(graph, [0.1, 0.1, -0.1], [0.1, 0.1, 0.1])
+    grid = ProblemReductions.GridGraph(ones(Bool, 2, 2), 1.2)
+    sg_square = ProblemReductions.SpinGlass(grid, [0.1, 0.3, -0.1, 0.4], [0.1, 0.1, 0.1, 0.2])
+    sg_square2 = ProblemReductions.SpinGlass(grid, [0.1, -0.3, 0.1, 0.4], [0.1, 0.1, 0.1, 0.2])
+    for (source, target_type) in [
+            sg_square => ProblemReductions.IndependentSet{ProblemReductions.GridGraph{2}, Float64, Vector{Float64}},
+            sg_square2 => ProblemReductions.IndependentSet{ProblemReductions.GridGraph{2}, Float64, Vector{Float64}},
+            sg => ProblemReductions.IndependentSet{ProblemReductions.GridGraph{2}, Float64, Vector{Float64}},
+            sg2 => ProblemReductions.IndependentSet{ProblemReductions.GridGraph{2}, Float64, Vector{Float64}},
+            is => ProblemReductions.IndependentSet{ProblemReductions.GridGraph{2}, Int, ProblemReductions.UnitWeight},
+            wis => ProblemReductions.IndependentSet{ProblemReductions.GridGraph{2}, Float64, Vector{Float64}},
+            fact => ProblemReductions.IndependentSet{ProblemReductions.GridGraph{2}, Int, Vector{Int}},
+        ]
+        @info "Testing reduction from $(typeof(source)) to $(target_type)"
+        # directly solve
+        best_source = ProblemReductions.findbest(source, ProblemReductions.BruteForce())
+
+        # reduce and solve
+        result = ProblemReductions.reduceto(target_type, source)
+        target = ProblemReductions.target_problem(result)
+        @test target isa target_type
+        #best_target = findbest(target, BruteForce())
+        best_target = GenericTensorNetworks.solve(GenericTensorNetwork(GenericTensorNetworks.IndependentSet(SimpleGraph(target.graph), collect(target.weights))), ConfigsMax())[].c.data
+
+        # extract the solution
+        best_source_extracted_single = unique( ProblemReductions.extract_solution.(Ref(result), best_target) )
+        best_source_extracted_multiple = ProblemReductions.extract_multiple_solutions(result, best_target)
+
+        # check if the solutions are the same
+        @test best_source_extracted_single ⊆ best_source
+        @test Set(best_source_extracted_multiple) == Set(best_source)
+    end
+end

test/runtests.jl

@@ -1,6 +1,10 @@
 using UnitDiskMapping
 using Test
 
+@testset "Core" begin
+    include("Core.jl")
+end
+
 @testset "utils" begin
     include("utils.jl")
 end
@@ -48,3 +52,7 @@ end
 @testset "visualize" begin
     include("visualize.jl")
 end
+
+@testset "reduceto" begin
+    include("reduceto.jl")
+end