game of life cellular automata using c++ vectors in openframeworks - c++

Question

I am building a game of life CA in C++ (openFrameworks). As I am new to C++ I was wondering if someone could let me know if I am setting up the vectors correctly in the following code. the CA does not draw to the screen and I am not sure if this is as a result of how I set up the vectors. I have to use 1D vectors as I intend to send data to Pure Data which only handles 1D structures.
GOL::GOL() {
init();
}
void GOL::init() {
for (int i =1;i < cols-1;i++) {
for (int j =1;j < rows-1;j++) {
board.push_back(rows * cols);
board[i * cols + j] = ofRandom(2);
}
}
}
void GOL::generate() {
vector<int> next(rows * cols);
// Loop through every spot in our 2D array and check spots neighbors
for (int x = 0; x < cols; x++) {
for (int y = 0; y < rows; y++) {
// Add up all the states in a 3x3 surrounding grid
int neighbors = 0;
for (int i = -1; i <= 1; i++) {
for (int j = -1; j <= 1; j++) {
neighbors += board[((x+i+cols)%cols) * cols + ((y+j+rows)%rows)];
}
}
// A little trick to subtract the current cell's state since
// we added it in the above loop
neighbors -= board[x * cols + y];
// Rules of Life
if ((board[x * cols + y] == 1) && (neighbors < 2)) next[x * cols + y] = 0; // Loneliness
else if ((board[x * cols + y] == 1) && (neighbors > 3)) next[x * cols + y] = 0; // Overpopulation
else if ((board[x * cols + y] == 0) && (neighbors == 3)) next[x * cols + y] = 1; // Reproduction
else next[x * cols + y] = board[x * cols + y]; // Stasis
}
}
// Next is now our board
board = next;
}

Answer 1

this looks weird in your code:
void GOL::init() {
for (int i =1;i < cols-1;i++) {
for (int j =1;j < rows-1;j++) {
board.push_back(rows * cols);
board[i * cols + j] = ofRandom(2);
}
}
}
"vector.push_back( value )" means "append value to the end of this vector" see std::vector::push_back reference
After doing this, you access the value of board[i * cols + j] and change it into a random value. What I think you are trying to do is:
void GOL::init() {
// create the vector with cols * rows spaces:
for(int i = 0; i < cols * rows; i++){
board.push_back( ofRandom(2));
}
}
This is how you would access every element at position x,y in your vector:
for (int x = 0; x < cols; x++) {
for (int y = 0; y < rows; y++) {
board[x * cols + y] = blabla;
}
}
This means that in void GOL::generate() you are not accessing the right position when you do this:
neighbors += board[((x+i+cols)%cols) * cols + ((y+j+rows)%rows)];
I think you want to do this:
neighbors += board[((x+i+cols)%cols) * rows + ((y+j+rows)%rows)];
so x * rows + y instead of x * cols + y