Why is this D code slower than C++?

[Bradley Smith]

Jacco Bikker wrote several raytracing articles on DevMaster.net. I took 
his third article and ported it to D. I was surprised to find that the D 
code is approx. 4 times slower than C++.

The raytracer_d renders in approx. 21 sec and the raytracer_cpp renders 
in approx. 5 sec. I am using the DMD and DMC compilers on Windows.

How can the D code be made to run faster?

Thanks,
   Bradley

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