Fastest way to read/store lots of multidimensional data? (Java)

Question

I have three questions about three nested loops:

for (int x=0; x<400; x++)
{
    for (int y=0; y<300; y++)
    {
        for (int z=0; z<400; z++)
          


        

Answer 1

public static void main( String[] args ) {

    int[][][] storage = new int[ 400 ][ 300 ][ 400 ];
    long start = System.currentTimeMillis();

    for ( int x = 0; x < 400; x++ ) {
        for ( int y = 0; y < 300; y++ ) {
            for ( int z = 0; z < 400; z++ ) {
                storage[x][y][z] = 5;
            }
        }
    }

    long end = System.currentTimeMillis();
    System.out.println( "Time was: " + ( end - start ) / 1000.0 + " seconds." );


}

Ran with -Xmx1g

Time was: 0.188 seconds.

That seems pretty darn fast.. you are looking at 48 MILLION elements in the innermost loop.

Homerolling a silly little datastructure..

public static void main( String[] args ) {

    StorerGuy[] storerGuys = new StorerGuy[ 400 ];

    long start = System.currentTimeMillis();

    for ( int x = 0; x < 400; x++ ) {
        for ( int y = 0; y < 300; y++ ) {
            for ( int z = 0; z < 400; z++ ) {
                storerGuys[x] = new StorerGuy( x, y, z, 5 );

            }
        }
    }

    long end = System.currentTimeMillis();
    System.out.println( "Time was: " + ( end - start ) / 1000.0 + " seconds." );

}

public static class StorerGuy {

    public int x;
    public int y;
    public int z;
    public int value;

    StorerGuy( int x, int y, int z, int value ) {
        this.x = x;
        this.y = y;
        this.z = z;
        this.value = value;
    }

}

Time was: 0.925 seconds.

Which is faster than 4 seconds you had in your mixed up order example.

I think multi arrays are too much for the problem. You are better off with a more complex data structure, as it will keep the stuff all in 1 memory location (x,y,z,value).

Java is an OO language. In most cases, you should use objects and not weird data structures like int[][][]