2D array problem...

Accelerated Computing CUDA CUDA Programming and Performance
1

Hi! External Image

I make this topic because I’m having a problem trying to implement a 2D array so that I can use it on the device.

The problem goes like this:

I need to use this structure: struct neighbor{
float3 neighbor1; → coordinates of the vertex corresponding to the row index;
float3 neighbor2; → the coordinates of the vertex2 and vertex3 wich makes a triangle;
float3 neighbor3;
};

so that in each member of the matrix has a structure like that.

I think that implementing it on the host it’s not that difficult, but the problem is how to get it to the device after…

Thanks in advance to anyone that replies.

2

Why is that gonna be a problem?

If you cudaMemcpy() this to the device it should work.

like:

neighbour * h_neighbour = new h_neighbour[NUM_NEIGHBOURS];

//fill h_neighbour with valid data

neighbour * d_neighbours = 0;

cudaMalloc(d_neighbours, sizeof(neighbour) * NUM_NEIGHBOURS);

cudaMemcpy(d_neighbour, h_neighbour, sizeof(neighbour) * NUM_NEIGHBOURS, cudaMemcpyHostToDevice);
3

Hi edisongustavo!

the main problem, that I’m not figuring out is how to fill the 2D array with data, since i’m declaring it as 1D array “cudaMalloc(d_neighbours, sizeof(neighbour) * NUM_NEIGHBOURS);” the array will have 2903 rows and 16 columns, and I don’t know hot put this on the memory.

Obrigado pelo post na mesma! Or thank you for the post (if you don’t know portuguese)

4

You can view a 2D array like this:

A B C
D E F
G H I

Or like this, which it most probably looks like in memory:

A B C D E F G H I

I’m not 100% sure I understand your problem correctly, but this may help.

5

Hi kristleifur

I’ve already saw this, and I think it will be part of the solution, the main problem, and of course it is very simple (only I can’t figure it out) is how to access it like a matrix. How can I access it using the indexes so I can store in the matrix like this:

for(int i=0;i<numvertex;i++){

	             for(int j=0;j<16;j++){

	

	                	matrix[i+j].neighbor1=make_float3(x,y,z);

			                 ^^^

                                             the problem is here

	             }

    }
6

You can make a 1D array look like a 2D array like kristle said, inside the 2nd for you can access it like this:

for (int i = 0; i < rows; ++i) {

  for (int j = 0; j < cols; ++j) {

  	unsigned int index = i * cols + j;

This wikipedia article explains this kind of access:

http://en.wikipedia.org/wiki/Row-major_order

PS.: Sim, eu entendo português, sou brasileiro :)