Why is this D code slower than C++?

[Bradley Smith]

As Bill Baxter pointed out, I missed an optimization on version 2. The 
pass by reference optimization using the inout on the Intersect's Ray 
argument. I had applied inout only to the Raytrace's Ray argument.

The further optimization brings the following approx. timings:

         time     factor
   dmc    5 sec    1.0
   dmd    9 sec    1.8
   gdc    13 sec   2.6
   msvc   5 sec    1.0
   g++    doesn't compile

Version 3 is attached and has the following changes:
   Fixed compiling with gdc
   Use inout for Intersect's Ray argument

Thanks,
   Bradley

Bradley Smith wrote:
> 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
> 
-------------- next part --------------
A non-text attachment was scrubbed...
Name: raytracer3_cpp_d_3.zip
Type: application/octet-stream
Size: 21214 bytes
Desc: not available
Url : http://lists.puremagic.com/pipermail/digitalmars-d-learn/attachments/20070118/a861c6ea/attachment-0001.obj