Optimizations

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Optimizations

When you're ready to optimize your game, this page can be helpful.

Distance

-- simple functions test timer by @antix
local random, sqrt = math.random, math.sqrt

local x1, y1 = random(-100000, 100000), random(-100000, 100000)
local x2, y2 = random(-100000, 100000), random(-100000, 100000)
local dx, dy

-- init test
local dist = math.distance(x1, y1, x2, y2)
print("*** POINT A: "..x1, y1, "POINT B: "..x2, y2)
print("*** DISTANCE: "..dist)

-- tests
local data = {
	{
		"sqrt",
		function()
			dx, dy = x2-x1, y2-y1
			dist = sqrt(dx*dx + dy*dy)
		end, -- 56ms
	},
	{
		"exponent",
		function()
			dx, dy = x2-x1, y2-y1
			dist = (dx^2 + dy^2)^0.5
		end, -- 40ms
	},
	{
		"multiply/exponent",
		function()
			dx, dy = x2-x1, y2-y1
			dist = (dx*dx + dy*dy)^0.5
		end, -- 43ms
	},
	{
		"multiply/exponent without power",
		function()
			dx, dy = x2-x1, y2-y1
			dist = dx*dx + dy*dy
		end, -- 40ms but wrong result!
	},
	{
		"math.distance",
		function()
			dist = math.distance(x1, y1, x2, y2)
		end, -- 73ms
	},
}

-- run all functions
for i = 1, #data do
	local block = data[i]
	local func = block[2]
	local start = os.timer()
	for i = 1, 1000000 do -- 1 million repetitions!
		func()
	end
	local elapsed = math.floor((os.timer() - start) * 1000)
	print(block[1].." ("..elapsed.."ms)", "", "", "", "", "distance: "..dist)
end

Sprite Sorting

-- sprite sorting (based on simple functions test timer by @antix)
local random = math.random

local sprites = {}
for i = 1, 64 do
	sprites[i] = {}
	sprites[i].spr1 = Pixel.new(0x0, 1, 64, 64)
	sprites[i].spr1:setPosition(random(1, 640), 48) -- 48, 96
	stage:addChild(sprites[i].spr1)
	sprites[i].spr2 = Pixel.new(0xff0000, 1, 64, 64)
	sprites[i].spr2:setPosition(random(1, 640), 64)
	stage:addChild(sprites[i].spr2)
end

local spr1y, spr2y = 0, 0

-- tests
local data = {
	{
		"swap",
		function()
			for _, v in pairs(sprites) do
				if v.spr1:getY() < v.spr2:getY() then
					spr1y, spr2y = v.spr1:getY(), v.spr2:getY()
					stage:swapChildren(v.spr1, v.spr2)
				end
			end
		end, -- 412ms (our winner!)
	},
	{
		"addChildAt",
		function()
			for _, v in pairs(sprites) do
				if v.spr1:getY() < v.spr2:getY() then
					spr1y, spr2y = v.spr1:getY(), v.spr2:getY()
					stage:addChildAt(v.spr1, stage:getChildIndex(v.spr2))
				end
			end
		end, -- 636ms
	},
}
 
-- run all functions
for i = 1, #data do
	local block = data[i]
	local func = block[2]
	local start = os.timer()
	for i = 1, 12500 do func() end
	local elapsed = math.floor((os.timer() - start) * 1000)
	print(block[1].." ("..elapsed.."ms)", spr1y, spr2y)
end

More to come, God's willing!

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