But in practice it&#x27;s quite often the case that you know optimisations are worth it based on past experience.<p>For example, with floating point calculations, divides are slower (on x86 anyway) than multiplies, so quite a common one in graphics&#x2F;physics is to calculate the reciprocal (1.0f &#x2F; x) and multiply by that if you&#x27;d do more than one divide in the first place.<p>The compiler <i>can</i> do this in some cases, but generally only with fpmath=fast, and even then, not always.