Lua Performance - Revision history

Gajop: remove ugly code blocks

2018-10-13T09:59:52Z

remove ugly code blocks

Picassoct: /* Test 13 */

2017-08-04T15:05:58Z

Test 13

← Older revision		Revision as of 16:05, 4 August 2017
Line 426:		Line 426:
	=Test 13=		=Test 13=
	Table initialisation with local members and static intialisation.		Table initialisation with local members and static intialisation.
			<code><pre>
	local x = os.clock()		local x = os.clock()
	T={}		T={}
Line 434:		Line 435:
	end		end
	print(string.format("elapsed time: %.2f\n", os.clock() - x))		print(string.format("elapsed time: %.2f\n", os.clock() - x))
			</pre></code>
			<code><pre>
	local x = os.clock()		local x = os.clock()
	A={}		A={}
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	end		end
	print(string.format("elapsed time: %.2f\n", os.clock() - x))		print(string.format("elapsed time: %.2f\n", os.clock() - x))
			</pre></code>
	Result:		Result:
	local table initializer = 100 %		local table initializer = 100 %

Picassoct: /* Lua Garbage Collection */

2017-08-04T15:04:55Z

Lua Garbage Collection

← Older revision		Revision as of 16:04, 4 August 2017
Line 423:		Line 423:

	[http://www.lua.org/gems/sample.pdf]		[http://www.lua.org/gems/sample.pdf]

			=Test 13=
			Table initialisation with local members and static intialisation.
			local x = os.clock()
			T={}
			print(string.format("start time: %.2f\n", os.clock() - x))
			local CachedTable= {"abc","def","ghk"}
			for i=1 , 10000000, 1 do
			T[i] = CachedTable
			end
			print(string.format("elapsed time: %.2f\n", os.clock() - x))

			local x = os.clock()
			A={}
			print(string.format("start time: %.2f\n", os.clock() - x))
			for i=1 , 10000000, 1 do
			A[i] = {"abc","def","ghk"}
			end
			print(string.format("elapsed time: %.2f\n", os.clock() - x))

			Result:
			local table initializer = 100 %
			static intializer = 500 %

			Analysis: Lua sucks at identifying static initializers, do not use them, use local initalizations instead.

	=Lua Garbage Collection=		=Lua Garbage Collection=

Beherith: /* TEST 12: Adding Table Items (mytable ={} vs. mytable={...}) */

2014-04-18T17:15:07Z

TEST 12: Adding Table Items (mytable ={} vs. mytable={...})

← Older revision		Revision as of 18:15, 18 April 2014
Line 421:		Line 421:

	If you write something like {[1] = true, [2] = true, [3] = true}, however, Lua is not smart enough to detect that the given expressions (literal numbers, in this case) describe array indices, so it creates a table with four slots in its hash part, wasting memory and CPU time		If you write something like {[1] = true, [2] = true, [3] = true}, however, Lua is not smart enough to detect that the given expressions (literal numbers, in this case) describe array indices, so it creates a table with four slots in its hash part, wasting memory and CPU time

			[http://www.lua.org/gems/sample.pdf]

	=Lua Garbage Collection=		=Lua Garbage Collection=

Beherith at 17:14, 18 April 2014

2014-04-18T17:14:42Z

@@ Line 387: / Line 387: @@
 '''Conclusion:'''
 :Don't use <code>table.insert</code>!!! Try to save the table-size somewhere and use <code>a[count+1]=x</code>!
 =Lua Garbage Collection=

Knorke: Garbage Collection

2013-10-26T08:53:48Z

Garbage Collection

← Older revision		Revision as of 09:53, 26 October 2013
Line 387:		Line 387:
	'''Conclusion:'''		'''Conclusion:'''
	:Don't use <code>table.insert</code>!!! Try to save the table-size somewhere and use <code>a[count+1]=x</code>!		:Don't use <code>table.insert</code>!!! Try to save the table-size somewhere and use <code>a[count+1]=x</code>!

			=Lua Garbage Collection=
			Forum thread about {{forumlink\|topic=31049\|title= Lua Garbage collection info}}

	[[Category: Lua]]		[[Category: Lua]]

Flozi: Add to Category: Lua

2011-05-05T20:15:51Z

Add to Category: Lua

← Older revision		Revision as of 21:15, 5 May 2011
Line 387:		Line 387:
	'''Conclusion:'''		'''Conclusion:'''
	:Don't use <code>table.insert</code>!!! Try to save the table-size somewhere and use <code>a[count+1]=x</code>!		:Don't use <code>table.insert</code>!!! Try to save the table-size somewhere and use <code>a[count+1]=x</code>!

			[[Category: Lua]]

Flozi: ...and the rest

2011-05-05T20:13:24Z

...and the rest

Show changes

Flozi: Start copying lua performance page from CA wiki (first 4 tests)

2011-05-05T19:48:18Z

Start copying lua performance page from CA wiki (first 4 tests)

New page

=Overview=

This page is copied from the [http://trac.caspring.org/wiki/LuaPerformance CA wiki]. The widget used in the performance tests is available from the [http://trac.caspring.org/browser/trunk/mods/ca-sandbox/LuaUI/Widgets/performance.lua CA SVN].

=Other Considerations=

It is a well known axiom in computing that
<blockquote>"We should forget about small efficiencies, say about 97% of the time: '''premature optimization is the root of all evil'''"</blockquote> - [http://en.wikipedia.org/wiki/Donald_Knuth Donald Knuth]

Lua coders should keep that in mind, and especially when visiting this page. Readability and maintainability are in most cases just as important, and optimizing code for every last ounce of performance can severely impact those qualities. On the other hand, some of the optimizations suggested have little bearing on readability and should generally always be applied, e.g. localization of API functions, or actually make for neater code e.g. the use of <code>or</code> rather than a nil-check. Generally speaking, optimize only once you are sure that there is or will be a performance bottleneck.

=Performance Tests=

==TEST 1: Localize==
'''Code:'''

<code><pre> local min = math.min</pre></code>

'''Results:'''

:Non-local: 0.719 (158%)
:Localized: 0.453 (100%)

'''Conclusion:'''

:Yes, we should localize all standard lua and Spring API functions.

==TEST 2: Localized Class-Methods (with only 3 accesses!)==
'''Code 1:'''

<code><pre> for i=1,1000000 do
local x = class.test()
local y = class.test()
local z = class.test()
end</pre></code>

'''Code 2:'''

<code><pre> for i=1,1000000 do
local test = class.test
local x = test()
local y = test()
local z = test()
end</pre></code>

'''Results:'''

:Normal way: 1.203 (102%)
:Localized: 1.172 (100%)

'''Conclusion:'''

:No, it isn't faster to localize a class method IN the function call.

==TEST 3: Unpack A Table==
'''Code 1:'''
<code><pre> for i=1,1000000 do
local x = min( a[1],a[2],a[3],a[4] )
end</pre></code>

'''Code 2:'''
<code><pre> local unpack = unpack
for i=1,1000000 do
local x = min( unpack(a) )
end</pre></code>

'''Code 3:'''
<code><pre> local function unpack4(a)
return a[1],a[2],a[3],a[4]
end
for i=1,1000000 do
local x = min( unpack4(a) )
end</pre></code>

'''Results:'''

:with [ ]: 0.485 (100%)
:unpack(): 1.093 (225%)
:custom unpack4: 0.641 (131%)

'''Conclusion:'''

:Don't use <code>unpack()</code> in time critical code!

==TEST 4: Determine Maximum And Set It ('>' vs. max)==
'''Code1:'''
<code><pre> local max = math.max
for i=1,1000000 do
x = max(random(cnt),x)
end</pre></code>

'''Code2:'''
<code><pre> for i=1,1000000 do
local r = random(cnt)
if (r>x) then x = r end
end</pre></code>

'''Results:'''

:math.max: 0.437 (156%)
:'if > then': 0.282 (100%)

'''Conclusion:'''

:Don't use math.[max|min]() in time critical code!