如何判断lua闭包和lua协程的权衡？（当它们都可以执行相同的任务时）

Question

ps：更不用说闭包实现同一任务的代码复杂度了。

Answer 1

闭包的内存开销将小于协程的内存开销（除非闭包中有很多“上值”，而协程中没有）。此外，调用闭包的时间开销可以忽略不计，而调用协程的开销则很小。据我所知，Lua 在协程切换方面做得非常好，但如果性能很重要并且您可以选择不使用协程，那么您应该探索该选项。

如果您想自己进行基准测试，对于 Lua 中的此操作或其他任何操作：

您可以使用 collectgarbage("collect");collectgarbage("count") 来报告所有非垃圾可收集内存的大小。 （您可能想要“收集”几次，而不仅仅是一次。）在创建某些东西（闭包、协程）之前和之后执行此操作，以了解它消耗了多少大小。

您可以使用 os.clock() 来计时。

另请参阅 Lua 编程关于分析。

Answer 2

参见：
https://gist.github.com/LiXizhi/911069b7e7f98db76d295dc7d1c5e34a

-- Testing coroutine overhead in LuaJIT 2.1 with NPL runtime
--[[ 
Starting function test...
memory(KB): 0.35546875
Functions:  500000
Elapsed time:   0    s
Starting coroutine test...
memory(KB): 13781.81640625
Coroutines: 500000
Elapsed time:   0.191    s
Starting single coroutine test...
memory(KB): 0.4453125
Coroutines: 500000
Elapsed time:   0.02800000000002
conclusions:
1. memory overhead: 0.26KB per coroutine
2. yield/resume pair overhead: 0.0004 ms
if you have 1000 objects each is calling yield/resume at 60FPS, then the time overhead is 0.2*1000/500000*60*1000 = 24ms
and if you do not reuse coroutine, then memory overhead is 1000*60*0.26 = 15.6MB/sec
]]

local total = 500000
local start, stop
function loopy(n)
  n = n + 1 
  return n
end

print "Starting function test..."
collectgarbage("collect");collectgarbage("collect");collectgarbage("collect");
local beforeCount =collectgarbage("count")
start = os.clock()
for i = 1, total do
  loopy(i)
end
stop = os.clock()
print("memory(KB):", collectgarbage("count") - beforeCount)
print("Functions:", total)
print("Elapsed time:", stop-start, " s")

print "Starting coroutine test..."
collectgarbage("collect");collectgarbage("collect");collectgarbage("collect");
local beforeCount =collectgarbage("count")
start = os.clock()
for i = 1, total do
  co = coroutine.create(loopy)
  coroutine.resume(co, i)
end
stop = os.clock()
print("memory(KB):", collectgarbage("count") - beforeCount)
print("Coroutines:", total)
print("Elapsed time:", stop-start, " s")


print "Starting single coroutine test..."
collectgarbage("collect");collectgarbage("collect");collectgarbage("collect");
local beforeCount =collectgarbage("count")
start = os.clock()
co = coroutine.create(function()
    for i = 1, total do
      loopy(i)
      coroutine.yield();
    end
end)

for i = 1, total do
  coroutine.resume(co, i)
end

stop = os.clock()
print("memory(KB):", collectgarbage("count") - beforeCount)
print("Coroutines:", total)
print("Elapsed time:", stop-start, " s")