Fastest Way to Append Multiple Elements to an Array

[MarcelDuchamp via Digitalmars-d-learn]

On Saturday, 20 December 2014 at 00:15:21 UTC, MarcelDuchamp 
wrote:
> On Friday, 19 December 2014 at 23:24:13 UTC, zeljkog wrote:
>> On 19.12.14 23:56, Ali Çehreli wrote:
>>> Can we see the test code please.
>>> 
>>> Ali
>>
>> import std.stdio, std.datetime, std.random;
>>
>> int N = 10_000;
>> int len = 1000;
>> int k = 4;
>>
>> struct S{
>>   int n1, n2;
>> //~ 	this(this){
>> //~ 		writeln("this(this)");
>> //~ 	}
>> }
>>
>> ref T[] append(T, Args...)(ref T[] arr, auto ref Args args)
>> {
>>   static if (args.length == 1)
>>      return arr ~= args[0];
>>   else{
>>      arr.length += args.length;
>>      foreach(i, ref e; args)
>>         arr[$ - args.length + i] = e;
>>      return arr;
>>   }
>> }
>>
>> void append1(T)(ref T[] arr, T[] args...)
>> {
>>   arr ~= args;
>> }
>>
>>
>> void main() {
>>   S[] arr1 = new S[len];
>>   S[] arr2, arr3, arr4, arr5;
>>   foreach (i; 0..len)
>>      arr1[i] = S(uniform(0, 100), uniform(0, 100));
>>   auto sw = new StopWatch;
>>
>>   sw.start();
>>   foreach(n; 0..N){
>>      for (int i = 0; i < len; i += k){
>>         arr2 ~= arr1[i];
>>         arr2 ~= arr1[i+1];
>>         arr2 ~= arr1[i+2];
>>         arr2 ~= arr1[i+3];
>> //~ 			arr2 ~= arr1[i+4];
>> //~ 			arr2 ~= arr1[i+5];
>>      }
>>      delete arr2;
>>   }
>>   sw.stop();
>>   long tm = sw.peek.msecs;
>>   writeln(tm);
>>
>>   sw.reset();
>>   sw.start();
>>   foreach(n; 0..N){
>>      for (int i = 0; i < len; i += k){
>>         arr3 ~= [arr1[i], arr1[i+1], arr1[i+2], arr1[i+3]/+  , 
>> arr1[i+4], arr1[i+5] +/];
>>      }
>>      delete arr3;
>>   }
>>   sw.stop();
>>   tm = sw.peek.msecs;
>>   writeln(tm);
>>
>>   sw.reset();
>>   sw.start();
>>   foreach(n; 0..N){
>>      for (int i = 0; i < len; i += k){
>>         arr4.append(arr1[i], arr1[i+1], arr1[i+2], arr1[i+3]/+
>>  , arr1[i+4], arr1[i+5] +/);
>>      }
>>      delete arr4;
>>   }
>>   sw.stop();
>>   tm = sw.peek.msecs;
>>   writeln(tm);
>>
>>   sw.reset();
>>   sw.start();
>>   foreach(n; 0..N){
>>      for (int i = 0; i < len; i += k){
>>         arr5.append1(arr1[i], arr1[i+1], arr1[i+2], 
>> arr1[i+3]/+   , arr1[i+4], arr1[i+5] +/);
>>      }
>>      delete arr5;
>>   }
>>   sw.stop();
>>   tm = sw.peek.msecs;
>>   writeln(tm);
>> }
>
> You've forget the array of ref version. (append the address of 
> the first data)
> And adding S to an array is biased. S is fucking only >>8<< 
> bytes. add more data to your struct.

Seriously, do you get what I mean: 'roger this'/'copy that' ?

on an 64 bit OS, to append a 8 bytes struct is the same as 
appending a pointer. It Becommes more interesting to make an 
array of pointer when the struct is bigger.
When I've read your test I just thought: buy a rope man, you 
don't get the thing...
You want to add things but what ? a pointer or full stack of 
values ? 8 bytes it's nothing...