Speed of complex<double> vs gsl_complex computations

[Pavel]

Hello!

I've installed GSL for use in Visual Studio Community 2017 following
instructions of the blog
https://solarianprogrammer.com/2020/01/26/getting-started-gsl-gnu-scientific
-library-windows-macos-linux/.

I've decided to measure speed of calculations of internal complex numbers
realization using template complex<double> (including header complex.h) and
realization of complex numbers in GSL library. For this purpose I've
calculated large vectors ( length 10000000) of some complex function (that
is actually frequency dependence of graphene conductivity). I've used speed
optimization /O2 and /DHAVE_INLINE compiler options. The calculation time of
the vector using gsl_complex numbers was 7 s, while using internal
complex<double> numbers took only 1s. Is it true that GSL complex numbers
work slower than internal realization or maybe I've missed some optimization
settings of GSL?