On Friday 22 January 2016 20:46:54 Marc Mutz wrote:
> Which one is faster? On a dual-core, probably QVector. On a 64-core
> processor, probably std::vector.
Running attached test program (4 cores + 2-fold HT), I get these numbers:
QVector;
1: 483
2: 492
4: 498
8: 503
16: 502
32: 513
64: 631
128: 615
256: 1070
512: 2202
1024: 3987
2048: 8531
4096: 16385
std::vector:
1: 132
2: 130
4: 125
8: 123
16: 140
32: 233
64: 370
128: 546
256: 994
512: 1931
1024: 3759
2048: 7383
4096: 14841
'Nuff said.
--
Marc Mutz <marc.m...@kdab.com> | Senior Software Engineer
KDAB (Deutschland) GmbH & Co.KG, a KDAB Group Company
Tel: +49-30-521325470
KDAB - The Qt Experts
#include <vector>
#include <QVector>
#include <thread>
#include <QThread>
#include <algorithm>
#include <chrono>
#include <iostream>
CONTAINER<int> make_vector(size_t size) {
CONTAINER<int> result;
result.resize(size);
std::iota(result.begin(), result.end(), 1);
return result;
}
int main() {
const auto numThreads = QThread::idealThreadCount();
const size_t jobs = 1024*1024;
for (int size = 1; size <= 1024*4; size *= 2) {
const auto v = make_vector(size);
std::vector<std::thread> threads;
threads.reserve(numThreads);
auto start = std::chrono::high_resolution_clock::now();
for (auto i = numThreads; i > 0; --i) {
threads.emplace_back([&v,jobs, size]() {
volatile int result = 0;
for (auto i = jobs; i > 0; --i) {
const auto v2 = v;
for (auto e : v2)
result += e;
}
});
}
for (auto &thread : threads)
thread.join();
auto end = std::chrono::high_resolution_clock::now();
std::cout << size << ": " << std::chrono::duration_cast<std::chrono::milliseconds>(end - start).count() << std::endl;
}
}
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