On 31 May 2013 21:05, Timon Gehr <timon.gehr@gmx.ch> wrote:

On 05/31/2013 12:58 PM, Joseph Rushton Wakeling wrote:

On 05/31/2013 08:34 AM, Manu wrote:

What's taking the most time?
The lighting loop is so template-tastic, I can't get a feel for how fast that
loop would be.

Hah, I found this out the hard way recently -- have been doing some experimental
reworking of code where some key inner functions were templatized, and it had a
nasty effect on performance. I'm guessing it made it impossible for the
compilers to inline these functions :-(

That wouldn't make any sense though, since after template expansion there is no difference between the generated version and a particular handwritten version.

Assuming that you would hand-write exactly the same code as the template expansion...

Typically template expansion leads to countless temporary redundancies, which you expect the compiler to try and optimise away, but it's not always able to do so, especially if there is an if() nearby, or worse, a pointer dereference.