Note that dynamic arrays are generic containers, so they aren't
exactly optimized for anything. You could try that test with
the "made for appending" std.array.appender: It always tries to
extend without reallocating, and only relocates when the
current memory segment is 100% full.
Furthermore, when it *does* relocate, it use D-style memmove
without calling postblit. Independent of language, and with the
requirement of contiguous memory, I can't really think of a
scheme that could be better than that...?
modified a bit (see below) to include timing etc. I'm on OSX
(16GB ram, core i7 2.3GHz).
dmd is slow even with optimizations so I used ldc:
ldmd2 -inline -O -release -noboundscheck (similar results with
ldc2 -O3 -release)
for C++: g++ -O2
It seems that:
* the number of moves is up to 2x (resp. 1.8x) as the C++ version
for T[] (resp. appender)
* the C++ version is 7x (resp 1.8x) times faster .
* it seems even the appender version grows super-linearly whereas
C++ version stays roughly linear in that regime in terms of time.
Based on this, I'm curious whether the current growing scheme
could be improved, or be closer to the simple doubling scheme
used in C++.
T[]: 94 s
appender!(T[]): 26.130
std::vector<T> (C++): 14.635s
D version with T[]:
Elements[0]: 1, Allocations: 1, Moved: 0; Moved/Elements = 0;
time/Elements=0
Elements[1]: 2, Allocations: 1, Moved: 0; Moved/Elements = 0;
time/Elements=0
Elements[2]: 4, Allocations: 1, Moved: 0; Moved/Elements = 0;
time/Elements=0
Elements[3]: 8, Allocations: 1, Moved: 0; Moved/Elements = 0;
time/Elements=0
Elements[4]: 16, Allocations: 2, Moved: 15; Moved/Elements =
0.9375; time/Elements=0
Elements[5]: 32, Allocations: 3, Moved: 46; Moved/Elements =
1.4375; time/Elements=0
Elements[6]: 64, Allocations: 4, Moved: 109; Moved/Elements =
1.70312; time/Elements=0
Elements[7]: 128, Allocations: 5, Moved: 236; Moved/Elements =
1.84375; time/Elements=0
Elements[8]: 256, Allocations: 6, Moved: 491; Moved/Elements =
1.91797; time/Elements=0
Elements[9]: 512, Allocations: 7, Moved: 1001; Moved/Elements =
1.95508; time/Elements=0
Elements[10]: 1024, Allocations: 8, Moved: 2023; Moved/Elements =
1.97559; time/Elements=0
Elements[11]: 2048, Allocations: 9, Moved: 4069; Moved/Elements =
1.98682; time/Elements=0
Elements[12]: 4096, Allocations: 9, Moved: 4069; Moved/Elements =
0.993408; time/Elements=0
Elements[13]: 8192, Allocations: 9, Moved: 4069; Moved/Elements =
0.496704; time/Elements=0
Elements[14]: 16384, Allocations: 9, Moved: 4069; Moved/Elements
= 0.248352; time/Elements=0
Elements[15]: 32768, Allocations: 9, Moved: 4069; Moved/Elements
= 0.124176; time/Elements=0
Elements[16]: 65536, Allocations: 9, Moved: 4069; Moved/Elements
= 0.062088; time/Elements=1.52588e-05
Elements[17]: 131072, Allocations: 9, Moved: 4069; Moved/Elements
= 0.031044; time/Elements=1.52588e-05
Elements[18]: 262144, Allocations: 9, Moved: 4069; Moved/Elements
= 0.015522; time/Elements=2.28882e-05
Elements[19]: 524288, Allocations: 10, Moved: 114644;
Moved/Elements = 0.218666; time/Elements=2.09808e-05
Elements[20]: 1048576, Allocations: 11, Moved: 745411;
Moved/Elements = 0.710879; time/Elements=2.19345e-05
Elements[21]: 2097152, Allocations: 12, Moved: 2342834;
Moved/Elements = 1.11715; time/Elements=2.24113e-05
Elements[22]: 4194304, Allocations: 13, Moved: 7344033;
Moved/Elements = 1.75095; time/Elements=2.19345e-05
Elements[23]: 8388608, Allocations: 13, Moved: 10469281;
Moved/Elements = 1.24804; time/Elements=2.18153e-05
Elements[24]: 16777216, Allocations: 13, Moved: 17981345;
Moved/Elements = 1.07177; time/Elements=2.15173e-05
Elements[25]: 33554432, Allocations: 14, Moved: 59359120;
Moved/Elements = 1.76904; time/Elements=2.18451e-05
Elements[26]: 67108864, Allocations: 14, Moved: 127885200;
Moved/Elements = 1.90564; time/Elements=2.17557e-05
Elements[27]: 134217728, Allocations: 15, Moved: 196579199;
Moved/Elements = 1.46463; time/Elements=2.16886e-05
Elements[28]: 268435456, Allocations: 14, Moved: 408059792;
Moved/Elements = 1.52014; time/Elements=2.19792e-05
Elements[29]: 536870912, Allocations: 14, Moved: 1094434704;
Moved/Elements = 2.03854; time/Elements=2.21152e-05
Elements[30]: 1073741824, Allocations: 14, Moved: 1874734992;
Moved/Elements = 1.74598; time/Elements=2.17576e-05
Elements[31]: 2147483648, Allocations: 13, Moved: 2723954593;
Moved/Elements = 1.26844; time/Elements=2.20812e-05
./test_010 91.65s user 2.97s system 99% cpu 1:34.79 total
D version with appender:
Elements[0]: 1, Allocations: 1, Moved: 0; Moved/Elements = 0;
time/Elements=0
Elements[1]: 2, Allocations: 1, Moved: 0; Moved/Elements = 0;
time/Elements=0
Elements[2]: 4, Allocations: 1, Moved: 0; Moved/Elements = 0;
time/Elements=0
Elements[3]: 8, Allocations: 1, Moved: 0; Moved/Elements = 0;
time/Elements=0
Elements[4]: 16, Allocations: 1, Moved: 0; Moved/Elements = 0;
time/Elements=0
Elements[5]: 32, Allocations: 2, Moved: 16; Moved/Elements = 0.5;
time/Elements=0
Elements[6]: 64, Allocations: 2, Moved: 16; Moved/Elements =
0.25; time/Elements=0
Elements[7]: 128, Allocations: 3, Moved: 80; Moved/Elements =
0.625; time/Elements=0
Elements[8]: 256, Allocations: 3, Moved: 80; Moved/Elements =
0.3125; time/Elements=0
Elements[9]: 512, Allocations: 4, Moved: 336; Moved/Elements =
0.65625; time/Elements=0
Elements[10]: 1024, Allocations: 4, Moved: 336; Moved/Elements =
0.328125; time/Elements=0
Elements[11]: 2048, Allocations: 5, Moved: 1360; Moved/Elements =
0.664062; time/Elements=0
Elements[12]: 4096, Allocations: 6, Moved: 3408; Moved/Elements =
0.832031; time/Elements=0
Elements[13]: 8192, Allocations: 6, Moved: 3408; Moved/Elements =
0.416016; time/Elements=0
Elements[14]: 16384, Allocations: 6, Moved: 3408; Moved/Elements
= 0.208008; time/Elements=0
Elements[15]: 32768, Allocations: 6, Moved: 3408; Moved/Elements
= 0.104004; time/Elements=0
Elements[16]: 65536, Allocations: 6, Moved: 3408; Moved/Elements
= 0.052002; time/Elements=0
Elements[17]: 131072, Allocations: 6, Moved: 3408; Moved/Elements
= 0.026001; time/Elements=0
Elements[18]: 262144, Allocations: 6, Moved: 3408; Moved/Elements
= 0.0130005; time/Elements=3.8147e-06
Elements[19]: 524288, Allocations: 7, Moved: 462160;
Moved/Elements = 0.8815; time/Elements=3.8147e-06
Elements[20]: 1048576, Allocations: 7, Moved: 527696;
Moved/Elements = 0.50325; time/Elements=4.76837e-06
Elements[21]: 2097152, Allocations: 9, Moved: 3083600;
Moved/Elements = 1.47038; time/Elements=5.24521e-06
Elements[22]: 4194304, Allocations: 9, Moved: 3304784;
Moved/Elements = 0.787922; time/Elements=5.00679e-06
Elements[23]: 8388608, Allocations: 9, Moved: 6622544;
Moved/Elements = 0.789469; time/Elements=5.36442e-06
Elements[24]: 16777216, Allocations: 10, Moved: 14069072;
Moved/Elements = 0.838582; time/Elements=5.36442e-06
Elements[25]: 33554432, Allocations: 10, Moved: 29244752;
Moved/Elements = 0.871562; time/Elements=5.42402e-06
Elements[26]: 67108864, Allocations: 10, Moved: 57773392;
Moved/Elements = 0.860891; time/Elements=5.39422e-06
Elements[27]: 134217728, Allocations: 11, Moved: 241548624;
Moved/Elements = 1.79968; time/Elements=5.93811e-06
Elements[28]: 268435456, Allocations: 10, Moved: 478076240;
Moved/Elements = 1.78097; time/Elements=5.68479e-06
Elements[29]: 536870912, Allocations: 9, Moved: 773229904;
Moved/Elements = 1.44025; time/Elements=5.64754e-06
Elements[30]: 1073741824, Allocations: 9, Moved: 1165659472;
Moved/Elements = 1.0856; time/Elements=5.46221e-06
Elements[31]: 2147483648, Allocations: 10, Moved: 3299478864;
Moved/Elements = 1.53644; time/Elements=6.32741e-06
./test_010 22.63s user 3.31s system 99% cpu 26.130 total
C++ version with std::vector:
g++ -O2 test8.cc -o test && time ./test
Elements[0] : 1 Allocations: 1 Moved: 0 Moved/Elements: 0
time/Elements: 0
Elements[1] : 2 Allocations: 2 Moved: 1 Moved/Elements: 0.5
time/Elements: 0
Elements[2] : 4 Allocations: 3 Moved: 3 Moved/Elements: 0.75
time/Elements: 0
Elements[3] : 8 Allocations: 4 Moved: 7 Moved/Elements: 0.875
time/Elements: 0
Elements[4] : 16 Allocations: 5 Moved: 15 Moved/Elements: 0.9375
time/Elements: 0
Elements[5] : 32 Allocations: 6 Moved: 31 Moved/Elements: 0.96875
time/Elements: 0
Elements[6] : 64 Allocations: 7 Moved: 63 Moved/Elements:
0.984375 time/Elements: 0
Elements[7] : 128 Allocations: 8 Moved: 127 Moved/Elements:
0.992188 time/Elements: 0
Elements[8] : 256 Allocations: 9 Moved: 255 Moved/Elements:
0.996094 time/Elements: 0
Elements[9] : 512 Allocations: 10 Moved: 511 Moved/Elements:
0.998047 time/Elements: 0
Elements[10] : 1024 Allocations: 11 Moved: 1023 Moved/Elements:
0.999023 time/Elements: 0
Elements[11] : 2048 Allocations: 12 Moved: 2047 Moved/Elements:
0.999512 time/Elements: 0
Elements[12] : 4096 Allocations: 13 Moved: 4095 Moved/Elements:
0.999756 time/Elements: 0
Elements[13] : 8192 Allocations: 14 Moved: 8191 Moved/Elements:
0.999878 time/Elements: 0
Elements[14] : 16384 Allocations: 15 Moved: 16383 Moved/Elements:
0.999939 time/Elements: 0
Elements[15] : 32768 Allocations: 16 Moved: 32767 Moved/Elements:
0.999969 time/Elements: 0
Elements[16] : 65536 Allocations: 17 Moved: 65535 Moved/Elements:
0.999985 time/Elements: 0
Elements[17] : 131072 Allocations: 18 Moved: 131071
Moved/Elements: 0.999992 time/Elements: 0
Elements[18] : 262144 Allocations: 19 Moved: 262143
Moved/Elements: 0.999996 time/Elements: 3.8147e-06
Elements[19] : 524288 Allocations: 20 Moved: 524287
Moved/Elements: 0.999998 time/Elements: 3.8147e-06
Elements[20] : 1048576 Allocations: 21 Moved: 1048575
Moved/Elements: 0.999999 time/Elements: 2.86102e-06
Elements[21] : 2097152 Allocations: 22 Moved: 2097151
Moved/Elements: 1 time/Elements: 2.86102e-06
Elements[22] : 4194304 Allocations: 23 Moved: 4194303
Moved/Elements: 1 time/Elements: 2.86102e-06
Elements[23] : 8388608 Allocations: 24 Moved: 8388607
Moved/Elements: 1 time/Elements: 3.09944e-06
Elements[24] : 16777216 Allocations: 25 Moved: 16777215
Moved/Elements: 1 time/Elements: 3.03984e-06
Elements[25] : 33554432 Allocations: 26 Moved: 33554431
Moved/Elements: 1 time/Elements: 3.15905e-06
Elements[26] : 67108864 Allocations: 27 Moved: 67108863
Moved/Elements: 1 time/Elements: 3.08454e-06
Elements[27] : 134217728 Allocations: 28 Moved: 134217727
Moved/Elements: 1 time/Elements: 3.09944e-06
Elements[28] : 268435456 Allocations: 29 Moved: 268435455
Moved/Elements: 1 time/Elements: 3.24473e-06
Elements[29] : 536870912 Allocations: 30 Moved: 536870911
Moved/Elements: 1 time/Elements: 3.32668e-06
Elements[30] : 1073741824 Allocations: 31 Moved: 1073741823
Moved/Elements: 1 time/Elements: 3.34531e-06
Elements[31] : 2147483648 Allocations: 32 Moved: 2147483647
Moved/Elements: 1 time/Elements: 3.36301e-06
real 0m14.635s
user 0m11.665s
sys 0m2.962s
----
import std.stdio;
import std.datetime;
import std.array;
static private StopWatch sw;//TEMP:move?
auto TIC(){
sw.reset();
sw.start();
}
auto TOC(){
sw.stop();
return sw.peek().msecs;
}
void main(){
enum N=32;
size_t maxElements=1;
alias ubyte T;
for (size_t iter=0;iter<N;iter++ , maxElements*=2) {
//if(iter<N-1) continue;
size_t totalElementsMoved = 0;
size_t totalAllocations = 0;
TIC();
version(none){
T[] s;
foreach (i; 0 .. maxElements) {
auto oldPtr = s.ptr;
s ~= 0;
if (s.ptr != oldPtr) {
totalElementsMoved += (s.length - 1);
++totalAllocations;
}
}
}
else{
auto s = appender!(T[])();
foreach (i; 0 .. maxElements) {
auto oldPtr = s.data.ptr;
s.put(cast(T)0);
if (s.data.ptr != oldPtr) {
totalElementsMoved += (s.data.length - 1);
++totalAllocations;
}
}
}
auto t=TOC();
writefln("Elements[%s]: %s, Allocations: %s, Moved: %s;
Moved/Elements = %s; time/Elements=%s",
iter, maxElements, totalAllocations, totalElementsMoved,
totalElementsMoved/cast(double)(maxElements),
t/cast(double)(maxElements));
}
}
----
----
#include <iostream>
#include <vector>
#include <sys/time.h>
#include <stdio.h>
#include <unistd.h>
using namespace std;
struct timeval start, end;
long mtime, seconds, useconds;
void tic(){
gettimeofday(&start, NULL);
}
long toc(){
gettimeofday(&end, NULL);
seconds = end.tv_sec - start.tv_sec;
useconds = end.tv_usec - start.tv_usec;
mtime = ((seconds) * 1000 + useconds/1000.0) + 0.5;
return mtime;
}
int main(){
int N=32;
size_t maxElements=1;
typedef unsigned char T;
for (size_t iter=0;iter<N;iter++ , maxElements*=2) {
vector<T> s;
size_t totalElementsMoved = 0;
size_t totalAllocations = 0;
tic();
for (size_t i = 0; i < maxElements; ++i) {
T *oldPtr = s.empty() ? NULL : &s[0];
s.push_back(0);
if (&s[0] != oldPtr) {
totalElementsMoved += (s.size() - 1);
++totalAllocations;
}
}
long t=toc();
cout << "Elements[" << iter << "] : " << maxElements
<< " Allocations: " << totalAllocations
<< " Moved: " << totalElementsMoved
<< " Moved/Elements: " <<
totalElementsMoved/static_cast<double>(maxElements)
<< " time/Elements: " <<
t/static_cast<double>(maxElements)
<< '\n';
}
}
----
