Steven Schveighoffer wrote:
>> I do see the point about allocation and reallocation -- what was
>> bothering me a bit was that even taking those aspects out of the code
>> and preallocating everything, I could write C++ code that _didn't_
>> preallocate and still ran (much) faster ... :-)
>
> If you are comparing vector's push_back to D's array append after
> pre-allocating, you are still not comparing apples to apples...
No ... ! That was true in the original code I posted, but following
bearophile's kind example that part of the code was updated to a form
along the lines of,
x.length = 5_000_000;
for(uint i=0;i<100;++i) {
size_t pos = 0;
for(uint j=0;j<5_000;++j) {
for(uint k=0;k<1_000;++k) {
x[pos++] = j*k;
}
}
}
... which in itself indeed runs about the same speed as C++. But that's
not the main cause of the difference in running time of the codes.
> D's standard library should have a construct that duplicates the
> performance of vector, I'm not sure if there is anything right now. I
> thought Appender would do it, but you have said in the past it is slow.
> This needs to be remedied.
It would be great -- but by itself it's not responsible for the timing
differences I'm observing.
Best wishes,
-- Joe
