Add efficient SparseVector method for some metrics (#235)

Project.toml

@@ -1,9 +1,10 @@
 name = "Distances"
 uuid = "b4f34e82-e78d-54a5-968a-f98e89d6e8f7"
-version = "0.10.6"
+version = "0.10.7"
 
 [deps]
 LinearAlgebra = "37e2e46d-f89d-539d-b4ee-838fcccc9c8e"
+SparseArrays = "2f01184e-e22b-5df5-ae63-d93ebab69eaf"
 Statistics = "10745b16-79ce-11e8-11f9-7d13ad32a3b2"
 StatsAPI = "82ae8749-77ed-4fe6-ae5f-f523153014b0"
 

src/Distances.jl

@@ -2,6 +2,7 @@ module Distances
 
 using LinearAlgebra
 using Statistics
+using SparseArrays: SparseVectorUnion, nonzeroinds, nonzeros, nnz
 import StatsAPI: pairwise, pairwise!
 
 export

src/bhattacharyya.jl

@@ -50,6 +50,32 @@ end
     return sqab, asum, bsum
 end
 
+@inline function _bhattacharyya_coeff(a::SparseVectorUnion{<:Number}, b::SparseVectorUnion{<:Number})
+    anzind = nonzeroinds(a)
+    bnzind = nonzeroinds(b)
+    anzval = nonzeros(a)
+    bnzval = nonzeros(b)
+    ma = nnz(a)
+    mb = nnz(b)
+
+    ia = 1; ib = 1
+    s = zero(typeof(sqrt(oneunit(eltype(a))*oneunit(eltype(b)))))
+    @inbounds while ia <= ma && ib <= mb
+        ja = anzind[ia]
+        jb = bnzind[ib]
+        if ja == jb
+            s += sqrt(anzval[ia] * bnzval[ib])
+            ia += 1; ib += 1
+        elseif ja < jb
+            ia += 1
+        else
+            ib += 1
+        end
+    end
+    # efficient method for sum for SparseVectorView is missing
+    return s, sum(anzval), sum(bnzval)
+end
+
 # Faster pair- and column-wise versions TBD...
 
 

src/metrics.jl

@@ -308,6 +308,55 @@ Base.@propagate_inbounds function _evaluate(d::UnionMetrics, a::AbstractArray, b
     end
 end
 
+eval_op_a(d, ai, b) = eval_op(d, ai, zero(eltype(b)))
+eval_op_b(d, bi, a) = eval_op(d, zero(eltype(a)), bi)
+
+# It is assumed that eval_reduce(d, s, eval_op(d, zero(eltype(a)), zero(eltype(b)))) == s
+# This justifies ignoring all terms where both inputs are zero.
+Base.@propagate_inbounds function _evaluate(d::UnionMetrics, a::SparseVectorUnion, b::SparseVectorUnion, ::Nothing)
+    @boundscheck if length(a) != length(b)
+        throw(DimensionMismatch("first array has length $(length(a)) which does not match the length of the second, $(length(b))."))
+    end
+    if length(a) == 0
+        return zero(result_type(d, a, b))
+    end
+    anzind = nonzeroinds(a)
+    bnzind = nonzeroinds(b)
+    anzval = nonzeros(a)
+    bnzval = nonzeros(b)
+    ma = nnz(a)
+    mb = nnz(b)
+    ia = 1; ib = 1
+    s = eval_start(d, a, b)
+    @inbounds while ia <= ma && ib <= mb
+        ja = anzind[ia]
+        jb = bnzind[ib]
+        if ja == jb
+            v = eval_op(d, anzval[ia], bnzval[ib])
+            ia += 1; ib += 1
+        elseif ja < jb
+            v = eval_op_a(d, anzval[ia], b)
+            ia += 1
+        else
+            v = eval_op_b(d, bnzval[ib], a)
+            ib += 1
+        end
+        s = eval_reduce(d, s, v)
+    end
+    @inbounds while ia <= ma
+        v = eval_op_a(d, anzval[ia], b)
+        s = eval_reduce(d, s, v)
+        ia += 1
+    end
+    @inbounds while ib <= mb
+        v = eval_op_b(d, bnzval[ib], a)
+        s = eval_reduce(d, s, v)
+        ib += 1
+    end
+    return eval_end(d, s)
+end
+
+
 _evaluate(dist::UnionMetrics, a::Number, b::Number, ::Nothing) = eval_end(dist, eval_op(dist, a, b))
 function _evaluate(dist::UnionMetrics, a::Number, b::Number, p)
     length(p) != 1 && throw(DimensionMismatch("inputs are scalars but parameters have length $(length(p))."))

test/test_dists.jl

@@ -1,5 +1,7 @@
 # Unit tests for Distances
 
+using SparseArrays: sparsevec, sprand
+
 struct FooDist <: PreMetric end # Julia 1.0 Compat: struct definition must be put in global scope
 
 @testset "result_type" begin
@@ -217,7 +219,7 @@ end
         for (_x, _y) in (([4.0, 5.0, 6.0, 7.0], [3.0, 9.0, 8.0, 1.0]),
                          ([4.0, 5.0, 6.0, 7.0], [3. 8.; 9. 1.0]))
             x, y = T.(_x), T.(_y)
-            for (x, y) in ((x, y),
+            for (x, y) in ((x, y), (sparsevec(x), sparsevec(y)),
                            (convert(Array{Union{Missing, T}}, x), convert(Array{Union{Missing, T}}, y)),
                            ((Iterators.take(x, 4), Iterators.take(y, 4))), # iterator
                            (((x[i] for i in 1:length(x)), (y[i] for i in 1:length(y)))), # generator
@@ -331,7 +333,8 @@ end # testset
 end #testset
 
 @testset "empty vector" begin
-    for T in (Float64, F64), (a, b) in ((T[], T[]), (Iterators.take(T[], 0), Iterators.take(T[], 0)))
+    for T in (Float64, F64), (a, b) in ((T[], T[]), (Iterators.take(T[], 0), Iterators.take(T[], 0)),
+                                        (sprand(T, 0, .1), sprand(T, 0, .1)))
         @test sqeuclidean(a, b) == 0.0
         @test isa(sqeuclidean(a, b), T)
         @test euclidean(a, b) == 0.0
@@ -391,6 +394,10 @@ end # testset
     @test_throws DimensionMismatch colwise!(mat23, Bregman(x -> sqeuclidean(x, zero(x)), x -> 2*x), mat23, mat22)
     @test_throws DimensionMismatch Bregman(x -> sqeuclidean(x, zero(x)), x -> 2*x)([1, 2, 3], [1, 2])
     @test_throws DimensionMismatch Bregman(x -> sqeuclidean(x, zero(x)), x -> [1, 2])([1, 2, 3], [1, 2, 3])
+    sv1 = sprand(10, .2)
+    sv2 = sprand(20, .2)
+    @test_throws DimensionMismatch euclidean(sv1, sv2)
+    @test_throws DimensionMismatch bhattacharyya(sv1, sv2)
 end # testset
 
 @testset "Different input types" begin
@@ -504,41 +511,43 @@ end
 
 @testset "bhattacharyya / hellinger" begin
     for T in (Int, Float64, F64)
-        x, y = T.([4, 5, 6, 7]), T.([3, 9, 8, 1])
-        a = T.([1, 2, 1, 3, 2, 1])
-        b = T.([1, 3, 0, 2, 2, 0])
-        p = T == Int ? rand(0:10, 12) : rand(T, 12)
-        p[p .< median(p)] .= 0
-        q = T == Int ? rand(0:10, 12) : rand(T, 12)
-
-        # Bhattacharyya and Hellinger distances are defined for discrete
-        # probability distributions so to calculate the expected values
-        # we need to normalize vectors.
-        px = x ./ sum(x)
-        py = y ./ sum(y)
-        expected_bc_x_y = sum(sqrt.(px .* py))
-        for (x, y) in ((x, y), (Iterators.take(x, 12), Iterators.take(y, 12)))
-            @test Distances.bhattacharyya_coeff(x, y) ≈ expected_bc_x_y
-            @test bhattacharyya(x, y) ≈ (-log(expected_bc_x_y))
-            @test hellinger(x, y) ≈ sqrt(1 - expected_bc_x_y)
-        end
+        _x, _y = T.([4, 5, 6, 7]), T.([3, 9, 8, 1])
+        _a = T.([1, 2, 1, 3, 2, 1])
+        _b = T.([1, 3, 0, 2, 2, 0])
+        _p = T == Int ? rand(0:10, 12) : rand(T, 12)
+        _p[_p .< median(_p)] .= 0
+        _q = T == Int ? rand(0:10, 12) : rand(T, 12)
+
+        for (x, y, a, b, p, q) in ((_x, _y, _a, _b, _p, _q), sparsevec.((_x, _y, _a, _b, _p, _q)))
+            # Bhattacharyya and Hellinger distances are defined for discrete
+            # probability distributions so to calculate the expected values
+            # we need to normalize vectors.
+            px = x ./ sum(x)
+            py = y ./ sum(y)
+            expected_bc_x_y = sum(sqrt.(px .* py))
+            for (x, y) in ((x, y), (Iterators.take(x, 12), Iterators.take(y, 12)))
+                @test Distances.bhattacharyya_coeff(x, y) ≈ expected_bc_x_y
+                @test bhattacharyya(x, y) ≈ (-log(expected_bc_x_y))
+                @test hellinger(x, y) ≈ sqrt(1 - expected_bc_x_y)
+            end
 
-        pa = a ./ sum(a)
-        pb = b ./ sum(b)
-        expected_bc_a_b = sum(sqrt.(pa .* pb))
-        @test Distances.bhattacharyya_coeff(a, b) ≈ expected_bc_a_b
-        @test bhattacharyya(a, b) ≈ (-log(expected_bc_a_b))
-        @test hellinger(a, b) ≈ sqrt(1 - expected_bc_a_b)
-
-        pp = p ./ sum(p)
-        pq = q ./ sum(q)
-        expected_bc_p_q = sum(sqrt.(pp .* pq))
-        @test Distances.bhattacharyya_coeff(p, q) ≈ expected_bc_p_q
-        @test bhattacharyya(p, q) ≈ (-log(expected_bc_p_q))
-        @test hellinger(p, q) ≈ sqrt(1 - expected_bc_p_q)
-
-        # Ensure it is semimetric
-        @test bhattacharyya(x, y) ≈ bhattacharyya(y, x)
+            pa = a ./ sum(a)
+            pb = b ./ sum(b)
+            expected_bc_a_b = sum(sqrt.(pa .* pb))
+            @test Distances.bhattacharyya_coeff(a, b) ≈ expected_bc_a_b
+            @test bhattacharyya(a, b) ≈ (-log(expected_bc_a_b))
+            @test hellinger(a, b) ≈ sqrt(1 - expected_bc_a_b)
+
+            pp = p ./ sum(p)
+            pq = q ./ sum(q)
+            expected_bc_p_q = sum(sqrt.(pp .* pq))
+            @test Distances.bhattacharyya_coeff(p, q) ≈ expected_bc_p_q
+            @test bhattacharyya(p, q) ≈ (-log(expected_bc_p_q))
+            @test hellinger(p, q) ≈ sqrt(1 - expected_bc_p_q)
+
+            # Ensure it is semimetric
+            @test bhattacharyya(x, y) ≈ bhattacharyya(y, x)
+        end
     end
 end #testset
 
@@ -769,7 +778,7 @@ end
 
     X = rand(ComplexF64, m, nx)
     Y = rand(ComplexF64, m, ny)
-    
+
     test_pairwise(SqEuclidean(), X, Y, Float64)
     test_pairwise(Euclidean(), X, Y, Float64)
 
@@ -946,6 +955,17 @@ end
     @test pairwise(PeriodicEuclidean(p), X, Y, dims=2)[1,2] == 0m
 end
 
+@testset "SparseVector, nnz(a) != nnz(b)" begin
+    for (n, densa, densb) in ((100, .1, .8), (200, .8, .1))
+        a = sprand(n, densa)
+        b = sprand(n, densb)
+        for d in (bhattacharyya, euclidean, sqeuclidean, jaccard, cityblock, totalvariation,
+                  chebyshev, braycurtis, hamming)
+            @test d(a, b) ≈ d(Vector(a), Vector(b))
+        end
+    end
+end
+
 #=
 @testset "zero allocation colwise!" begin
     d = Euclidean()