Question

I have an array, called x, whose size is 6*sizeof(float). I’m aware that declaring:

float x[6];

would allocate 6*sizeof(float) for x in the stack memory. However, if I do the following:

float *x;   // in class definition

x = new float[6];   // in class constructor

delete [] x;    // in class destructor

I would be allocating dynamic memory of 6*sizeof(float) to x. If the size of x does not change for the lifetime of the class, in terms of best practices for cleanliness and speed (I do vaguely recall, if not correctly, that stack memory operations are faster than dynamic memory operations), should I make sure that x is statically rather than dynamically allocated memory? Thanks in advance.

Answer 1

Declaring the array of fixed size will surely be faster. Each separate dynamic allocation requires finding an unoccupied block and that’s not very fast.

So if you really care about speed (have profiled) the rule is if you don’t need dynamic allocation – don’t use it. If you need it – think twice on how much to allocate since reallocating is not very fast too.