Null references redux + Cyclone

[Andrei Alexandrescu]

Christopher Wright wrote:
> bearophile wrote:
>> Jeremie Pelletier:
>>> Again, that's a lazy view on programming. High level constructs are 
>>> useful to isolate small and simple algorithms which are implemented 
>>> at low level.
>>
>> Software is inherently multi-scale. Probably in 90-95% of the code of 
>> a program micro-optimizations aren't that necessary because those 
>> operations are done only once in a while. But then it often happens 
>> that certain loops are done an enormous amount of times, so even small 
>> inefficiencies inside them lead to low performance. That's why 
>> profiling helps.
>>
>> This can be seen by how HotSpot (and modern dynamic language JITters 
>> work): usually virtual calls like you can find in a D program are 
>> quick, they don't slow down code. Yet if a dynamic call prevents the 
>> compile to perform a critical inlining or such dynamic call is left in 
>> the middle of a critical code, it may lead to a slower program. That's 
>> why I have Java code go 10-30% faster than D code compiled with LDC, 
>> not because of the GC and memory allocations, but just because LDC 
>> isn't smart enough to inline certain virtual methods.
> 
> Certainly agreed on virtual calls: on my machine, I timed a simple 
> example as executing 65 interface calls per microsecond, 85 virtual 
> calls per microsecond, and 210 non-member function calls per 
> microsecond. So you should almost never worry about the cost of 
> interface calls since they're so cheap, but they are 3.5 times slower 
> than non-member functions.

Thanks for posting these interesting numbers. I seem to recall that 
interface dispach in D does a linear search in the interfaces list, so 
you may want to repeat your tests with a variable number of interfaces, 
and a variable position of the interface being used.

Andrei