fix chisq_dist(0, 0)

fixes #59

Author: alyst

src/metrics.jl

@@ -239,7 +239,7 @@ corr_dist(a::AbstractArray, b::AbstractArray) = evaluate(CorrDist(), a, b)
 result_type(::CorrDist, a::AbstractArray, b::AbstractArray) = result_type(CosineDist(), a, b)
 
 # ChiSqDist
-@inline eval_op(::ChiSqDist, ai, bi) = abs2(ai - bi) / (ai + bi)
+@inline eval_op(::ChiSqDist, ai, bi) = ifelse(ai != bi, abs2(ai - bi) / (ai + bi), zero(ai))
 @inline eval_reduce(::ChiSqDist, s1, s2) = s1 + s2
 chisq_dist(a::AbstractArray, b::AbstractArray) = evaluate(ChiSqDist(), a, b)
 

test/test_dists.jl

@@ -161,6 +161,8 @@ end
             @test wminkowski(x, y, w, 2) ≈ weuclidean(x, y, w)
         end
 
+        # Test ChiSq doesn't give NaN at zero
+        @test chisq_dist([0.0], [0.0]) == 0.0
 
         # Test weighted Hamming distances with even weights
         a = T.([1.0, 2.0, 1.0, 3.0, 2.0, 1.0])