高精度计时器

wiki

此计时器由我的基准测试工具包 BenchmarkModule 使用。

HiResTimer.lua

---------------------------
-- this module provide a function
-- HiResTimer.clock() which returns a high resolution timer
---------------------------
module("HiResTimer",package.seeall)

--
-- take the alien module
--
local alien=require"alien"

--
-- get the kernel dll
--
local kernel32=alien.load("kernel32.dll")

--
-- get dll functions
--
local QueryPerformanceCounter=kernel32.QueryPerformanceCounter
QueryPerformanceCounter:types{ret="int",abi="stdcall","pointer"}
local QueryPerformanceFrequency=kernel32.QueryPerformanceFrequency
QueryPerformanceFrequency:types{ret="int",abi="stdcall","pointer"}

--------------------------------------------
--- utility : convert a long to an unsigned long value
-- (because alien does not support longlong nor ulong)
--------------------------------------------
local function lu(long)
	return long<0 and long+0x80000000+0x80000000 or long
end

--------------------------------------------
--- Query the performance frequency.
-- @return (number)
--------------------------------------------
local function qpf()
	local frequency=alien.array('long',2)
	QueryPerformanceFrequency(frequency.buffer)
	return  math.ldexp(lu(frequency[1]),0)
		    +math.ldexp(lu(frequency[2]),32)
end

--------------------------------------------
--- Query the performance counter.
-- @return (number)
--------------------------------------------
local function qpc()
	local counter=alien.array('long',2)
	QueryPerformanceCounter(counter.buffer)
	return	 math.ldexp(lu(counter[1]),0)
			+math.ldexp(lu(counter[2]),32)
end

--------------------------------------------
-- get the startup values
--------------------------------------------
local f0=qpf()
local c0=qpc()

--------------------------------------------
--- Return a hires clock
-- @return (number) elapsed seconds since load of the module
--------------------------------------------
function clock()
	local c1=qpc()
	return (c1-c0)/f0
end

return HiResTimer

示例，使用方法

local hrt=require"HiResTimer"

local t0=hrt.clock()

for i=1,1000*1000 do
	local j=i*i
end

local t1=hrt.clock()

print("Took",t1-t0,"seconds")

Linux？

HiResTimer 与 socket.gettime()

我一直使用 LuaSocket? 的 gettime 函数作为通用的高精度计时器。它在 Windows、Linux 和 BSD 上似乎运行良好。此外，LuaSocket? 通常已经存在。 -ScottVokes?

对我来说，socket.gettime() 的精度不够高。请查看此计时器。

local hrt=require"HiResTimer"
local socket=require"socket"
local function printf(...)
    io.write(string.format(...))
end
for loops=0,100000,1000 do
    printf("%6d loops ",loops)
    local t0=hrt.clock()
    for i=1,loops do local j=math.sin(123) end
    local t1=hrt.clock()
    printf("hrt=%9.3f ms",(t1-t0)*1000)
    local t0=socket.gettime()
    for i=1,loops do local j=math.sin(123) end
    local t1=socket.gettime()
    printf(" socket=%9.3f ms\n",(t1-t0)*1000)
    --if t1>t0 then  break end
end

     0 loops hrt=    0.035 ms socket=    0.000 ms
  1000 loops hrt=    0.327 ms socket=    0.000 ms
  2000 loops hrt=    0.461 ms socket=    0.000 ms
  3000 loops hrt=    0.685 ms socket=    0.000 ms
  4000 loops hrt=    0.905 ms socket=    0.000 ms
  5000 loops hrt=    1.123 ms socket=    0.000 ms
  6000 loops hrt=    1.391 ms socket=    0.000 ms
  7000 loops hrt=    1.565 ms socket=    0.000 ms
  8000 loops hrt=    1.801 ms socket=   15.625 ms
  9000 loops hrt=    2.032 ms socket=    0.000 ms
 10000 loops hrt=    2.244 ms socket=    0.000 ms
:::
 90000 loops hrt=   22.061 ms socket=   15.625 ms
 91000 loops hrt=   20.248 ms socket=   31.250 ms
 92000 loops hrt=   22.713 ms socket=   15.625 ms
 93000 loops hrt=   22.575 ms socket=   15.625 ms
 94000 loops hrt=   21.200 ms socket=   15.625 ms
 95000 loops hrt=   22.974 ms socket=   15.625 ms
 96000 loops hrt=   21.370 ms socket=   31.250 ms
 97000 loops hrt=   23.359 ms socket=   31.250 ms
 98000 loops hrt=   21.953 ms socket=   15.625 ms
 99000 loops hrt=   22.304 ms socket=   15.625 ms
100000 loops hrt=   22.887 ms socket=   15.625 ms

（至少在 Windows 上）socket.gettime 的分辨率为 64 滴答/秒，hires 中使用的性能计数器超过 1000000 滴答/秒（确切值可能因机器而异）

为了完整起见，我在 Linux 机器上检查了 socket.gettime

local socket=require"socket"
local function printf(...)
	io.write(string.format(...))
end
for loops=0,100000,1000 do
	printf("%6d loops ",loops)
	local t0=socket.gettime()
	for i=1,loops do local j=math.sin(123) end
	local t1=socket.gettime()
	printf(" socket=%9.3f ms\n",(t1-t0)*1000)
end

     0 loops  socket=    0.002 ms
  1000 loops  socket=    0.509 ms
  2000 loops  socket=    1.017 ms
  3000 loops  socket=    1.485 ms
  4000 loops  socket=    1.172 ms
  5000 loops  socket=    1.477 ms
  6000 loops  socket=    1.776 ms
  7000 loops  socket=    2.078 ms
  8000 loops  socket=    2.381 ms
  9000 loops  socket=    2.850 ms
 10000 loops  socket=    3.000 ms
::::
 90000 loops  socket=   25.086 ms
 91000 loops  socket=   25.474 ms
 92000 loops  socket=   25.696 ms
 93000 loops  socket=   25.991 ms
 94000 loops  socket=   26.368 ms
 95000 loops  socket=   26.634 ms
 96000 loops  socket=   26.922 ms
 97000 loops  socket=   27.096 ms
 98000 loops  socket=   27.463 ms
 99000 loops  socket=   27.776 ms
100000 loops  socket=   27.973 ms

- JoergenVonBargen

上面的 socket.gettime() 代码在 Mac OS X 上运行良好（在 10.6.5 上测试）

结果

     0 loops  socket=    0.001 ms
  1000 loops  socket=    0.156 ms
  2000 loops  socket=    0.264 ms
  3000 loops  socket=    0.399 ms
  4000 loops  socket=    0.529 ms
  5000 loops  socket=    0.667 ms
...
 96000 loops  socket=   12.948 ms
 97000 loops  socket=   12.678 ms
 98000 loops  socket=   12.718 ms
 99000 loops  socket=   12.963 ms
100000 loops  socket=   12.949 ms

-- DougCurrie

另请参阅

• [Lua/APR time_now] 也提供亚微秒级的时间测量。