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Passing 2D Arrays Fast

General and Gameplay Programming Programming

Started by Bong May 05, 2002 01:28 PM

5 comments, last by Bong 21 years, 11 months ago

Bong

122

Author

May 05, 2002 01:28 PM

Hey, does anybody know the fastest way to pass a 2d array of structures to a function? - Bong, James Bong

- Bong, James Bong

a person

118

May 05, 2002 01:33 PM

  return_type function_name(struct_type **arrayname, otherargs,){// code here}//or is using linear 2d arraysreturn_type function_name(struct_type *arrayname, otherargs,){// code here}

you cant get faster then just passing the address for the array.

Bong

122

Author

May 05, 2002 02:00 PM

Yeah, I guess that''d work the fastest, but my compiler gives me an error whenever I try to return a pointer to a 2d array. This is my function:

Tile** Map::GetTiles()
{
return TileMap;
}

TileMap is delcared as:

Tile TileMap[256][256];

However, I get an error saying "cannot convert Tile(*)[256] to Tile**

Do I have to return TileMap as a Tile*[256]?
Will that slow my program down any?

- Bong, James Bong

- Bong, James Bong

Oluseyi

2,123

May 05, 2002 02:12 PM

Bong

122

Author

May 05, 2002 02:23 PM

Now the compiler gives me an error saying "cannot convert Tile* to Tile**"

I tried changing it to

return &(&(TileMap[0][0]));

but it gives me an error saying "not a 1value"

- Bong, James Bong

- Bong, James Bong

Kippesoep

892

May 05, 2002 02:31 PM

The problem is that you''re trying to convert to an array of arrays to an array of pointers, which seems to work the same, but really isn''t. Anyway, you can pass it along as a linear array:

  void fill128x256 (int *array){  for (int y = 0; y < 128; y++)  {    for (int x = 0; x < 256; x++)    {       array [y * 256 + x] = rand ();    }  }}void useless (){  int myarray [128][256];  fill128x256 (&(myarray [0][0]));}

Also, take a look at this thread, in which I have also posted a class to encapsulate this behaviour.