Fix SVD of matrices with zero sizes (#125)

Author: andreasnoack

src/svd.jl

@@ -161,6 +161,10 @@ function __svd!(
 ) where {T<:Real}
 
     n = size(B, 1)
+    if n == 0
+        # Exit early in the empty case
+        return nothing
+    end
     n1 = 1
     n2 = n
     d = B.dv

test/svd.jl

@@ -68,6 +68,19 @@ using Test, GenericLinearAlgebra, LinearAlgebra, Quaternions, DoubleFloats
         @test A ≈ U * Diagonal(S) * V'
     end
 
+    @testset "Empty matrices. Issue 70" begin
+        @test svdvals!(Float16.(ones(10, 0))) == Float16[]
+        @test svdvals!(Float16.(ones(0, 10))) == Float16[]
+        U, s, Vt = svd!(Float16.(ones(10, 0)))
+        @test U == Matrix{Float16}(undef, 10, 0)
+        @test s == Float16[]
+        @test Vt == Matrix{Float16}(undef, 0, 0)
+        U, s, Vt = svd!(Float16.(ones(0, 10)))
+        @test U == Matrix{Float16}(undef, 0, 0)
+        @test s == Float16[]
+        @test Vt == Matrix{Float16}(undef, 10, 0)
+    end
+
     @testset "Very small matrices. Issue 79" begin
         A = randn(1, 2)
         FA = svd(A)