Is there a speed difference in using an array, struct or class?

Question

I need to do calculations based on a variable anmount of data, each item in the data containing 3 values. I could use an array, struct or a class to represent one of the items.

Is there any difference in speed or do they behave all the same way?

// #1: Only arrays
typedef int triple[3];

// #2: Using a struct
struct triple {
    int a;
    int b;
    int c;
};

// #3: Using a class
class triple {
public:
    int a;
    int b;
    int c;
};

Why not get it working first in a way that's intuitive to you? Who cares how fast an incomplete program is? — GManNickG, Jan 20 '12 at 23:40
Don't worry about the wrong stuff. First get it working. Then profile or *[random pause](http://stackoverflow.com/questions/375913/what-can-i-use-to-profile-c-code-in-linux/378024#378024)* to see what you need to be concerned about, if anything. — Mike Dunlavey, Jan 21 '12 at 02:09

score 7 · Accepted Answer · answered Jan 20 '12 at 23:35

7

Structs and classes are the same as far as that goes. As long as you use a constant index, all the math is done at compile time, so it shouldn't make any difference.

answered Jan 20 '12 at 23:35

smparkes

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What do you mean with *As long as you use a constant index*? – Niklas R Jan 21 '12 at 00:15
1

triple[0] should be the same as tripple.a. triple[i] would require a little bit of runtime math (a very little ...) – smparkes Jan 21 '12 at 00:18
I see, thanks, that is something I did not think about. :) Even it might not be very significant. – Niklas R Jan 21 '12 at 00:22

score 1 · Answer 2 · answered Jan 20 '12 at 23:36

1

There should be definitely no difference between struct and class with public: at the beginning and I suspect there will be no difference with array as well. Not at run time.

answered Jan 20 '12 at 23:36

Michael Krelin - hacker

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Is there a speed difference in using an array, struct or class?

2 Answers2