Merged in facaiy/eigen/ENH/exp_support_complex_for_gpu (pull request PR-359)

ENH: exp supports complex type for cuda

Eigen/src/Core/MathFunctions.h

diff --git a/Eigen/src/Core/MathFunctions.h b/Eigen/src/Core/MathFunctions.h
index 5ba5293..1b864a4 100644
--- a/Eigen/src/Core/MathFunctions.h
+++ b/Eigen/src/Core/MathFunctions.h
@@ -1289,6 +1289,22 @@
 
 template<> EIGEN_DEVICE_FUNC EIGEN_ALWAYS_INLINE
 double exp(const double &x) { return ::exp(x); }
+
+template<> EIGEN_DEVICE_FUNC EIGEN_ALWAYS_INLINE
+std::complex<float> exp(const std::complex<float>& x) {
+  auto com = ::expf(x.real());
+  auto res_real = com * ::cosf(x.imag());
+  auto res_imag = com * ::sinf(x.imag());
+  return std::complex<float>(res_real, res_imag);
+}
+
+template<> EIGEN_DEVICE_FUNC EIGEN_ALWAYS_INLINE
+std::complex<double> exp(const std::complex<double>& x) {
+  auto com = ::exp(x.real());
+  auto res_real = com * ::cos(x.imag());
+  auto res_imag = com * ::sin(x.imag());
+  return std::complex<double>(res_real, res_imag);
+}
 #endif
 
 template<typename Scalar>