[Numpy-discussion] How a transition to C++ could work

Sturla Molden sturla@molden...
Sun Feb 19 09:38:01 CST 2012


Den 19.02.2012 10:52, skrev Mark Wiebe:
>
>     C++ removes some of this advantage -- now there is extra code
>     generated by
>     the compiler to handle constructors, destructors, operators etc
>     which can
>     make a material difference to fast inner loops. So you end up just
>     writing
>     "C-style" anyway.
>
>
> This is in fact not true, and writing in C++ style can often produce 
> faster code. A classic example of this is C qsort vs C++ std::sort. 
> You may be thinking of using virtual functions in a class hierarchy, 
> where a tradeoff between performance and run-time polymorphism is 
> being done. Emulating the functionality that virtual functions provide 
> in C will give similar performance characteristics as the C++ language 
> feature itself.

I agree with Mark here. C++ usually produces the faster code. C++ has 
abstractions that makes it easier to write more efficient code. C++ 
provides more and better information to the compiler (e.g. strict 
aliasing rules). C++ compilers are also getting insanely good at 
optimisation, usually better than C compilers. But C++ also makes it 
easy to write sluggish bloatware, so the effect on performance is not 
predictable.

Sturla

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