索引协调最佳实践？ 按位运算与模和除法

Question

While building my 2D game using unity, I started indexing my tiles coordinate for easy access in a dictionary with the following code:

Public class Coordinate
{
    private short[] coordinate = new Int16[2];

    public Coordinate(In16 x, Int16 y)[...]
    public Int16 x {[...]}
    public Int16 y {[...]}

    public Int32 Key
    {
        get{
            return ((Int32)(y << 16) ^ x);
        }
    }

    public static void Coordinate(Coordinate coordinate, Int32 index)
    {
        coordinate.X = (Int16)(index >> 16);
        coordinate.y = (Int16)index;
    }
}

But eventually I found a quite simpler solution:

int index = y * mapWidth + x;

and

int x = index % mapWidth;
int y = index / mapWidth;

My question is this : Is any of these two method more safe for porting on different platform or just a better practice in general? If yes, is like to know the specifics.

Answer 1

Use Lsl or lsr is not a good practice because every body don't understand how it work even if it's faster than other solutions.

Divisions are the worst solution because it's not natural for computers and they can take a lot of time (yeah less than 1 ms but too many time even so). And imagine if you have a mapwith equal to 0.

i don't know for modulo but I think this is not a bad solution.

Multiplication can be the best solution or the worst. It depend of the number (2^x = best solution, (2^x)-1= worst solution (I think this is right for arm assembly) it's like multiply by 3. In assembly you should multiply by 2 and add the number. x*3 = x*2 + x. For humans it's the same, not for computers. Maybe compiler make the transition because they are smarter than in the past.

In this case I think multiplications are the best solution. Just change << by a basic multiplication (2^16, so 65536)

I don't know what you want to do with your code but according to comments you should split index into 2 variables. So vector2 is a good solution and easily to manage so a good practice.

I'm sorry for my poor English. If you don't understand something tell me I will try again :)

Have a nice day