Optimization tips - Revision history

Svengali: added category Oolite

2018-03-25T15:39:43Z

added category Oolite

Astrobe: /* Oolite Javascript Optimization tips */

2017-10-17T17:58:12Z

‎Oolite Javascript Optimization tips

Astrobe: /* Quick and easy performance boosts */

2017-10-17T17:45:18Z

‎Quick and easy performance boosts

Astrobe: /* Oolite Javascript Optimization tips */

2017-10-17T17:40:59Z

‎Oolite Javascript Optimization tips

Astrobe: /* Unclassified */

2017-09-24T17:09:29Z

‎Unclassified

Astrobe: /* Unclassified */

2017-09-24T17:08:43Z

‎Unclassified

Astrobe: /* Foreword */

2017-09-24T17:07:26Z

‎Foreword

Astrobe: /* Unclassified */

2017-09-24T17:04:51Z

‎Unclassified

Astrobe: /* Unclassified */

2017-09-24T17:03:53Z

‎Unclassified

Astrobe: /* Unclassified */

2017-09-24T16:56:48Z

‎Unclassified

← Older revision		Revision as of 15:39, 25 March 2018
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	''TODO'': don't know what to do with the second part of [http://www.aegidian.org/bb/viewtopic.php?f=4&t=18837&start=30#p257319\|link]		''TODO'': don't know what to do with the second part of [http://www.aegidian.org/bb/viewtopic.php?f=4&t=18837&start=30#p257319\|link]
		+
		+	[[Category:Oolite_scripting]]

← Older revision		Revision as of 17:58, 17 October 2017
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	The properties .heading and .vectorForward are always identical (verified in the source code). And they are always unit vectors, so there's no need to use .direction() on them directly. If your callback uses both, just pick one. .heading is easier to type but .vectorForward is nearer (in Ship vs Entity) and that's one less get in your profile.		The properties .heading and .vectorForward are always identical (verified in the source code). And they are always unit vectors, so there's no need to use .direction() on them directly. If your callback uses both, just pick one. .heading is easier to type but .vectorForward is nearer (in Ship vs Entity) and that's one less get in your profile.
		+
		+	== Memory managment ==
		+
		+	Javascript is a garbage collected language. This means that it automatically removes from memory the objects that are no longer used.
		+	However, this automatic memory management requires computations to determine which objects are "dead" and which are not. This is done in "garbage collection cycles" that may require significant time and cause a stutter in-game. The more objects a script generates, the more work for the garbage collector. There are some techniques to mitigate this.
		+
		+	The single most effective thing is to re-use objects whenever possible. Take arrays:
		+	<pre>
		+	mylist = [];
		+	</pre>
		+
		+	... is fine for initializing one but that is the only time this statement should be used. If you're doing this to clear an array (& remove references so objects in the list can be GC'd, a laudable goal), what you're really doing is assigning 'mylist' a brand new, empty array, and if 'mylist' is its only reference, you are succeeding in your goal but only as a side-effect. By assigning '[ ]' to your variable, you're tossing the old array (& all its references) on to the garbage heap. :)
		+
		+	If you want to clear and re-use an array, all you need to do is:
		+	<pre>
		+	mylist.length = 0;
		+	</pre>
		+
		+	and your array will be as empty as it was when it started. And yes, all the references to objects that were in your list are gone and they'll be GC'd. This seems counterintuitive, and there is a lot of debate as to whether this works across all implementations of JS, but is does work in Oolite, which is all we care about.
		+
		+	Before you go and convert all your arrays to this.$variables, remember Day's trick for assigning function references to properties of a function:
		+	<pre>
		+	this._myfunction = function _myfunction() { // NB: the 2nd '_myfunction' names the function, useful in stack dumps and profiling too
		+	var that = _myfunction;
		+	var random = (that.random = that.random \|\| Math.random);
		+	var mylist = (that.mylist = that.mylist \|\| []);
		+
		+	mylist.length = 0;
		+	...
		+	}
		+	</pre>
		+
		+	Now '_myfunction' will re-use the same array each time it's called, not creating a new one every time with mylist = [];
		+
		+	This same trick works for dictionary objects, that some functions require as parameters:
		+
		+	<pre>
		+	var missionConfig = {titleKey: "oolite-contracts-cargo-none-available-title",
		+	messageKey: "oolite-contracts-cargo-none-available-message",
		+	allowInterrupt: true,
		+	screenID: "oolite-contracts-cargo-none",
		+	exitScreen: "GUI_SCREEN_INTERFACES"};
		+	mission.runScreen(missionConfig);
		+	</pre>
		+
		+	This will create a new object every time it's invoked. But if we do the same as above:
		+	<pre>
		+	var missionConfig = (that.missionConfig = that.missionConfig \|\| {});
		+	...
		+	missionConfig.titleKey = "oolite-contracts-cargo-none-available-title";
		+	missionConfig.messageKey = "oolite-contracts-cargo-none-available-message";
		+	missionConfig.allowInterrupt = true;
		+	missionConfig.screenID = "oolite-contracts-cargo-none";
		+	missionConfig.exitScreen = "GUI_SCREEN_INTERFACES";
		+	mission.runScreen(missionConfig);
		+	</pre>
		+
		+	we'll only consume a single object here for the entire game.
		+
		+	There is a function in the debug console, console.writeJSMemoryStats(), that writes out some handy info:
		+	<pre>
		+	JavaScript heap: 19.48 MiB (limit 32.00 MiB, 7 collections to date)
		+	</pre>

	== Unsorted ==		== Unsorted ==

← Older revision		Revision as of 17:45, 17 October 2017
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	----		----
		+
		+	The properties .heading and .vectorForward are always identical (verified in the source code). And they are always unit vectors, so there's no need to use .direction() on them directly. If your callback uses both, just pick one. .heading is easier to type but .vectorForward is nearer (in Ship vs Entity) and that's one less get in your profile.

	== Unsorted ==		== Unsorted ==

@@ Line 26: / Line 26: @@
 [http://www.aegidian.org/bb/viewtopic.php?f=4&t=18837&start=45#p258473| link to the BB post]
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@@ Line 127: / Line 154: @@
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 ''TODO'': don't know what to do with the second part of [http://www.aegidian.org/bb/viewtopic.php?f=4&t=18837&start=30#p257319|link]

← Older revision		Revision as of 17:09, 24 September 2017
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−	== ~~Unclassified~~ ==	+	== Unsorted ==

← Older revision		Revision as of 17:08, 24 September 2017
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	----		----

		+	All Oolite-provided functions which take a vector as an argument may instead be passed an array of three numbers, or an Entity (in which case the entity’s position is used) [emphasis added]
		+
		+	So, use '''ps.position.distanceTo( ent )''' instead of '''ps.position.distanceTo( ent.position )'''
		+
		+	it profiles as 15% faster and you don't have to type positoin as often :) Sometimes it does pay to rtfm

@@ Line 14: / Line 14: @@
 To use the built-in profiler, you need the Debug Console. You just need to run something like :time worldScripts["snoopers"].calcNewDate() or console.profile(function() { [...] }); to get profiling information about the function you want to examine.
 [http://www.aegidian.org/bb/viewtopic.php?f=4&t=18837#p257063|link]
 ----

@@ Line 122: / Line 122: @@
 * x < 0 ? -x : x; instead of Math.abs(x), is over 10 x's faster.
 * x < y ? x : y; instead of Math.min(x, y), is over 12 x's faster (same for max).
 ----

← Older revision		Revision as of 17:03, 24 September 2017
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	If that's the only reference, garbage collection will do the rest. The delete command removes the property 'x' from the script's object, is an expensive op and not necessary. (esp. if you do 'x= addFrameCallback(...)' in shipWillLaunchFromStation)		If that's the only reference, garbage collection will do the rest. The delete command removes the property 'x' from the script's object, is an expensive op and not necessary. (esp. if you do 'x= addFrameCallback(...)' in shipWillLaunchFromStation)
		+
		+	----
		+
		+	* ship.checkScanner() is "usually considerably quicker than system.filteredEntities()" according to the wiki
		+	* There are also system.entitiesWithScanClass, system.shipsWithRole and system.shipsWithPrimaryRole which are much faster too.
		+	* (entitiesWithScanClass is about 10x faster). And if all you need is the #, there are partner fns countEntitiesWithScanClass,
		+	* countShipsWithRole, and countShipsWithPrimaryRole
		+	* missionVariables are extremely slow, some say 60 x's (profiling shows their only half as slow as WorldScriptsGetProperty :shock: )
		+	* x < 0 ? -x : x; instead of Math.abs(x), is over 10 x's faster.
		+	* x < y ? x : y; instead of Math.min(x, y), is over 12 x's faster (same for max).

	----		----

@@ Line 98: / Line 98: @@
 Doing this, I have sped my code by at least a factor of 40.
 (Which is not always enough...)
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@@ Line 119: / Line 114: @@
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