Go and generic programming on reddit, also touches on D

[Don]

On 19.09.2011 18:12, Andrei Alexandrescu wrote:
> On 9/19/11 10:46 AM, Robert Jacques wrote:
>> So, on balance, I'd say the two pointers representation is categorically
>> worse than the fat pointer representation.
>
> Benchmark. A few of your assumptions don't hold.
>
> Andrei

Note that high-performance libraries that use slices, like GMP and the 
many BLAS libraries, use the pointer+length representation, not 
pointer+pointer. They've done a lot of benchmarking on a huge range of 
architectures, with a large range of compilers.

The underlying reason for this, is that almost all CISC instruction sets 
have built-in support for pointer+length. AFAIK nothing has builtin 
support for ptr+ptr.

On x86, you have this wonderful [EAX+8*EBX] addressing mode, that can be 
used on almost every instruction, so that the calculation [addr + 
sz*index] takes ZERO clock cycles when sz is a power of 2.
Generally, when you supply two pointers, the optimizer will try to 
convert it into ptr + offset (where offset isn't bytes, it corresponds 
to D's length).