added missing matrix exponentiation methods (#29782)

JuliaLang · Oct 30, 2018 · de278a5 · de278a5
1 parent aa72f72
commit de278a5
Show file tree

Hide file tree

Showing 2 changed files with 11 additions and 0 deletions.
diff --git a/stdlib/LinearAlgebra/src/dense.jl b/stdlib/LinearAlgebra/src/dense.jl
@@ -467,6 +467,10 @@ julia> exp(A)
 exp(A::StridedMatrix{<:BlasFloat}) = exp!(copy(A))
 exp(A::StridedMatrix{<:Union{Integer,Complex{<:Integer}}}) = exp!(float.(A))
 
+Base.:^(b::Number, A::AbstractMatrix) = exp!(log(b)*A)
+# method for ℯ to explicitly elide the log(b) multiplication
+Base.:^(::Irrational{:ℯ}, A::AbstractMatrix) = exp(A)
+
 ## Destructive matrix exponential using algorithm from Higham, 2008,
 ## "Functions of Matrices: Theory and Computation", SIAM
 function exp!(A::StridedMatrix{T}) where T<:BlasFloat

diff --git a/stdlib/LinearAlgebra/test/dense.jl b/stdlib/LinearAlgebra/test/dense.jl
@@ -428,6 +428,13 @@ end
         end
     end
 
+    @testset "^ tests" for elty in (Float32, Float64, ComplexF32, ComplexF64, Int32, Int64)
+        # should all be exact as the lhs functions are simple aliases
+        @test ℯ^(fill(elty(2), (4,4))) == exp(fill(elty(2), (4,4)))
+        @test 2^(fill(elty(2), (4,4))) == exp(log(2)*fill(elty(2), (4,4)))
+        @test 2.0^(fill(elty(2), (4,4))) == exp(log(2.0)*fill(elty(2), (4,4)))
+    end
+
     A8 = 100 * [-1+1im 0 0 1e-8; 0 1 0 0; 0 0 1 0; 0 0 0 1]
     @test exp(log(A8)) ≈ A8
 end