ndarray: elementwise power for irrational (#310)

NEWS.md

@@ -51,6 +51,11 @@
     * `x.^y`
     * where `x` and `y` are `NDArray`s.
 
+* Elementwise power of irrational and `NDArray` (#TBD)
+    * `e.^x`
+    * `x.^e`
+    * `π.^x`
+
 ## API Changes
 
 * `reshape` of NDArray shares the same interface with Base (#272).

src/base.jl

@@ -157,11 +157,12 @@ end
 #
 # TODO: find a better solution in case this cause issues in the future.
 ################################################################################
-dump_mx_param(val::Any) = string(val)
-dump_mx_param(val::Float64) = @sprintf("%.16e", val)
-dump_mx_param(val::Float32) = @sprintf("%.8e", val)
-dump_mx_param(val::Float16) = @sprintf("%.4e", val)
-dump_mx_param(shape::NTuple{N, T}) where {N, T<:Integer} =
+dump_mx_param(val::Any)        = string(val)
+dump_mx_param(val::Float64)    = @sprintf("%.16e", val)
+dump_mx_param(val::Float32)    = @sprintf("%.8e", val)
+dump_mx_param(val::Float16)    = @sprintf("%.4e", val)
+dump_mx_param(val::Irrational) = @sprintf("%.16e", val)
+dump_mx_param(shape::NTuple{N, <:Integer}) where N =
   string(tuple(flipdim([shape...], 1)...))
 
 

src/ndarray.jl

@@ -754,6 +754,10 @@ broadcast_(::typeof(^), x::NDArray, y::NDArray) = _power(x, y)
 broadcast_(::typeof(^), x::NDArray, s::Real) = _power_scalar(x, scalar=s)
 broadcast_(::typeof(^), s::Real, x::NDArray) = _rpower_scalar(x, scalar=s)
 
+broadcast_(::typeof(^), ::Irrational{:e}, x::NDArray) = exp(x)
+broadcast_(::typeof(^), x::NDArray, s::Irrational) = _power_scalar(x, scalar=s)
+broadcast_(::typeof(^), s::Irrational, x::NDArray) = _rpower_scalar(x, scalar=s)
+
 """
     fill!(x, arr::NDArray)
 

test/unittest/ndarray.jl

@@ -516,6 +516,22 @@ function test_power()
     @test copy(y.^x) == Float32[2 4; 8 16]
   end
 
+  info("NDArray::power::e.^x::x.^e")
+  let x = mx.zeros(2, 3), A = [1 1 1; 1 1 1]
+    @test copy(e.^x) ≈ A
+  end
+
+  let A = Float32[1 2; 3 4], x = mx.NDArray(A)
+    @test copy(e.^x) ≈ e.^A
+    @test copy(x.^e) ≈ A.^e
+  end
+
+  info("NDArray::power::π.^x::x.^π")
+  let A = Float32[1 2; 3 4], x = mx.NDArray(A)
+    @test copy(π.^x) ≈ π.^A
+    @test copy(x.^π) ≈ A.^π
+  end
+
   # TODO: Float64: wait for https://github.com/apache/incubator-mxnet/pull/8012
 end # function test_power