Handle exp_generic(0.0)

SciML · Aug 16, 2020 · 172920f · 172920f
1 parent 452ca61
commit 172920f
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diff --git a/src/exp.jl b/src/exp.jl
@@ -116,7 +116,11 @@ by Higham, Nicholas J. in 2005 for algorithm details.
 """
 function exp_generic(x, vk=Val{13}())
     nx = opnorm(x, 1)
-    s = ceil(Int, log2(nx))
+    nxl2 = log2(nx)
+    if iszero(nx)
+        return x + oneunit(x)
+    end
+    s = ceil(Int, nxl2)
     if s >= 1
         exp_generic(x/(2^s), vk)^(2^s)
     else

diff --git a/test/runtests.jl b/test/runtests.jl
@@ -37,6 +37,11 @@ using ForwardDiff
     @test ForwardDiff.derivative(exp_generic, 0.1) == exp_generic(0.1)
 end
 
+@testset "Issue 42" begin
+    @test exp_generic(0.0) == 1
+    @test ForwardDiff.derivative(exp_generic, 0.0) == 1
+end
+
 @testset "Phi" begin
     # Scalar phi
     K = 4