How to prevent using global arrays in iteration in the module

[genkuroki]

@CRquantum

You example seems does not have a loop.

No.

The function LifeGame.gif!(board, niters; ...) in my example contains the for loop updating niters times the global variables initialized by boardrandom = LifeGame.randboard() and board5x5 = LifeGame.fivexfive() outside the module LifeGame and plotting each step to gif animations.

In the module LifeGame:

@genkuroki

function gif!(board::Board, niters, nskips=1; gifname="life.gif", fps=20, size=(240, 240))
    prog = Progress(niters, 0)
    anim = @animate for t in 1:niters
        heatmap(board.state; size, colorbar=false, ticks=false, axis=false, frame=false)
        update!(board, nskips)
        next!(prog)
    end
    gif(anim, gifname; fps)
end

Outside the module LifeGame:

@genkuroki

boardrandom = LifeGame.randboard()
LifeGame.gif!(boardrandom, 500; gifname="liferandom.gif")

@genkuroki

board5x5 = LifeGame.fivexfive()
LifeGame.gif!(board5x5, 2000; gifname="life5x5.gif", fps=60)

LifeGame.update!(board, niters) is not used in the example, but can update a LifeGame.Board type variable without plotting.

In the module LifeGame:

@genkuroki

function update!(board::Board, niters=1)
    state, tmp = board.state, board.tmp
    for _ in 1:niters÷2
        _update!(tmp, state)
        _update!(state, tmp)
    end
    if isodd(niters)
        _update!(tmp, state)
        state .= tmp
    end
end

The array tmp, which is used as a temporary workspace, is created by the constructor of LifeGame.Board objects.

@genkuroki

struct Board{T}
    state::T
    tmp::T
end
Board(state) = Board(state, similar(state))

Example of LifeGame.update!: Glider

Updating a global variable with a for loop can be done by passing it as an argument to a function containing a for loop.

state = Int8[
    0 0 0 0 0 0 0
    0 0 0 0 0 0 0
    0 0 0 0 0 0 0
    0 0 0 0 0 0 0
    0 1 1 0 0 0 0
    1 0 1 0 0 0 0
    0 0 1 0 0 0 0
]
board = LifeGame.Board(state)
board.state

7×7 Matrix{Int8}:
 0  0  0  0  0  0  0
 0  0  0  0  0  0  0
 0  0  0  0  0  0  0
 0  0  0  0  0  0  0
 0  1  1  0  0  0  0
 1  0  1  0  0  0  0
 0  0  1  0  0  0  0

↓
↓ update the global variable board 12 times
↓ by the for loop in the function LifeGame.update!
↓

LifeGame.update!(board, 12)
board.state

7×7 Matrix{Int8}:
 0  0  0  0  0  0  0
 0  0  0  0  1  1  0
 0  0  0  1  0  1  0
 0  0  0  0  0  1  0
 0  0  0  0  0  0  0
 0  0  0  0  0  0  0
 0  0  0  0  0  0  0

↓
↓ update and animate the global variable board
↓

LifeGame.gif!(board, 27; gifname="lifeglider.gif", fps=5)

Have fun!

Jupyter notebook: https://github.com/genkuroki/public/blob/main/0014/Game%20of%20Life.ipynb