MATLAB: The Game of Life explodes with rule 1133

cellular automatagame of life

Actually the patterns are respected in most of the Game of Life rules, not only the classical one which is Life2333 or B23/S3. The problem is that with a specific rule B1/S3 it doesn't work. I tried different rearrangement of the code, always the same problem with rule B1/S3.

Here a paper on Rule1133.

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Vladimiro - all cells in the image go white not because all cells alive but rather because all cells are dead. I think that this colouring behaviour is just due to the use of pcolor. For example,

 L = 50;
 x = 0:L;
 y = 0:L;
 pcolor(x,y,zeros(L+1,L+1));

produces the same figure as does

 pcolor(x,y,ones(L+1,L+1));

So all cells being the same colour does not necessarily mean that all cells are alive, but rather that all cells have the same state. And that state, in your case, is that all cells are dead. Why?

Review your birth and survival rules. I found that if I used

 Sur = [1]; 
 Bor = [2 3];

then I observed a much better evolution that spanned 100 generations. Check out the patterns at Game of Life to ensure that your software behaves in an identical manner for each of the pattern. (You may need to change the survival and birth rules 2,3 and 3 respectively. If you do so, you will observe - with your last defined initial population - the blinker pattern.) Also, just after the drawnow add a pause of 0.25 milliseconds using

 pause(0.25)

just to pause the script and control slow the flow from one iteration to the next.

Related Solutions

MATLAB: Game of Life rules using switch statement.

Josh - from Game of Life, there are four rules that need to be applied given the state of the cell, three of which are appropriate if the cell is live and one for when the cell is dead. So you have two "objects" to consider - the state of the cell and the rule to apply. Typically, I would use a switch statement only if I had one object (or its state) to be concerned with. In this case, you could use a switch statement on the state of the cell and then, if needed, use a switch statement on the neighbours. Something like

 switch isCellAlive

     case true

         switch numNeighbours

             case {0,1}
                 % live cell has fewer than two neighbours and so dies

             case {2,3}
                 % live cell has 2 0r 3 neighbours and so lives

             otherwise
                 % live cell dies due to over-population
         end

     case false

         if numNeighbours == 3
            % dead cell becomes live
         end
 end

Note that isCellAlive indicates the state of the cell (live or dead, true or false) and that numNeighbours indicates the number of live cells or neighbours.

So are there any advantages to using a switch in the above? I'm not sure. It does work because we only have a small set of integers that are appropriate for each of the cases (0 or 1, or 2 or 3). If you had larger ranges (say all positive integers between 1 and 25) then an if condition would be easier to use than doing case {1,2,3,4,etc.}. I think that the above code is as readable this way or if we were to use an if/elseif block.

MATLAB: Conway’s Game of Life implementation

Limbert - I think that part of the problem might be with how your if and elseif statements are not being properly "ended". For example, MATLAB may be interpreting this code

        	if B(i,j) == 1 % Cell is currently alive


            	    if (sum(sum(C)) < 3) || (sum(sum(C)) > 4)
                	B(i,j) = 0; % Dies


        	elseif B(i,j) == 0 % Cell is currently dead


            	    if sum(sum(C)) == 3
                	B(i,j) = 1; % Is born


            	end
              end
         end

              if B(i,j) == 1 % Cell is currently alive
            	    if (sum(sum(C)) < 3) || (sum(sum(C)) > 4)
                	B(i,j) = 0; % Dies
        	    elseif B(i,j) == 0 % Cell is currently dead
            	        if sum(sum(C)) == 3
                	    B(i,j) = 1; % Is born
            	        end
            	    end
              end

Once you have finished with an if/elseif/else block, then you need to properly close it with an end. Your code might then become

              if B(i,j) == 1 % Cell is currently alive
            	    if (sum(sum(C)) < 3) || (sum(sum(C)) > 4)
                	B(i,j) = 0; % Dies
             	    end             % <-------------------------- this is important!!
        	elseif B(i,j) == 0 % Cell is currently dead
            	    if sum(sum(C)) == 3
                	B(i,j) = 1; % Is born
            	    end
             	end

Also, rather than executing the same calculation 2-3 times, just do it once

numberOfNeighbours = sum(sum(C));

and use this variable when comparing against three or four.

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Related Solutions

MATLAB: Game of Life rules using switch statement.

MATLAB: Conway’s Game of Life implementation

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