Question

I’m working on a 2d Game. I use lua script in all game logic. Now the problem is the sorting too slow. Can anyone help to improve it?

Here is my code about zobject list.

local c = class("ZList") -- class is a function to generate a "Class"

function c:insert(v) -- every v(value or object) has a z field
    if v.z == nil then v.z = -1 end
    if self.head == nil then
        self.head = {val=v, nxt=nil}
    else
        local p = self.head
        local pp = p -- pp is a pointer to pre node
        while v.z and p and p.val.z and p.val.z <= v.z do
            pp = p
            p = p.nxt
        end
        if p == self.head then
            self.head = {val=v, nxt=p}
        else
            pp.nxt = {val=v, nxt=p}
        end
    end
end

function c:delete(v)
    local p = self.head
    local pp
    while p and p.val ~= v do
        pp = p
        p = p.nxt
    end

    if p ~= nil then
        if p == self.head then
            self.head = p.nxt
        else
            pp.nxt = p.nxt
        end
    end
end

___ update ______

Thank you Nicol and every replied! I followed your suggestion: use table.insert and table.sort, use a static list which don’t need to be sort. Here are my final codes:

    local remove_list
    sort(Graphics.viewports, comp)
    for _, viewport in pairs(Graphics.viewports) do
        if viewport.visible then
            remove_list = {}
            if not viewport.static then sort(viewport.sprites, comp) end
            for k, sprite in pairs(viewport.sprites) do
                if not sprite:paint() then
                    table.insert(remove_list,1, k)
                end
            end
            for _, k in pairs(remove_list) do
                table.remove(viewport.sprites, k)
            end
        end
    end

Answer 1

Stop putting your sprites in a linked list. Put them in a regular list. Insertion time is not going to hurt you nearly as badly as the memory allocations and such for a linked list will. Just use a regular Lua list, with table.insert and so forth.

Alternatively, do you really need all of your sprites to be sorted? Most likely (depending on the circumstances of course), you can just draw them in layers: all of Layer 0 (in any order), then all of Layer 1, etc.