I have a object which has a few base variables (integers as example) and one int
ID: 659015 • Letter: I
Question
I have a object which has a few base variables (integers as example) and one intermediate variable for further processing. The intermediate variable can be calculated from the base vars. Now the question: Should I always repeat the calculation of the intermediate var from the base vars or should I save the value and only change it if the base vars change? (I need access to every var in pseudo random order.)
Two examples in C++-Code.
Caching the result:
class Test
{
private:
int a;
int b;
int c;
int x;
void calcX ()
{
// Just an example for a calculation for x.
x = ((a + 10) * (b / (c*c + 1)));
}
public:
void setA (int var)
{
a = var;
calcX();
}
void setB (int var)
{
b = var;
calcX();
}
void setC (int var)
{
c = var;
calcX();
}
// Every var has a get methode.
}
Always recalculating the result:
class Test
{
private:
int a;
int b;
int c;
int x;
public:
// Var a, b and c have get and set methodes.
int getX ()
{
return ((a + 10) * (b / (c*c + 1)));
}
}
So, which way is considered better? I really don't know. We should not save the intermediate value because it would be redundant, but then again we should not recalculate the value again and again.
Explanation / Answer
It depends.
If you need to calculate once, and use million times, then the answer is obvious: the first case wins.
If you need to calculate every time, or quite often, then pick what you prefer. Your function doesn't read from a file, and has no slow operations, so it will not make a huge difference.
Avoid premature optimization.
When optimizing, it is best to measure. Profile the code and optimize only the bottlenecks. Everything else is a microoptimization, and should be avoided.
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