const sf::Time delta = sf::seconds(1.f / 60.f);
sf::Time stock;
sf::Clock clock;
while(!m_quit)
{
stock += clock.restart();
while(stock >= delta)
{
update();
stock -= delta;
}//while stock >= delta
render();
}//while not m quit
I wrote clock.getElapsedTime() in the first line of the while loop, which made the game go at a rate that is cubic in respect to time, instead of linear.