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From "Maurice Nicholson (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (FLEX-33273) CSSCondition.matchesStyleClient() is slow and creates excessive garbage
Date Tue, 27 Nov 2012 20:19:58 GMT

     [ https://issues.apache.org/jira/browse/FLEX-33273?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Maurice Nicholson updated FLEX-33273:
-------------------------------------

    Attachment: PerformanceTest.zip

Find attached the performance test project I am using for benchmarking. As I said it is based
on Grant Skinner's PerformanceTest v2 Beta.

Note that I am only testing the part of the algorithm inside the "if (kind == CSSConditionKind.CLASS)
{...}" block.

Before uploading, I cleaned it up a bit and added a few more possible alternatives... on my
machine running in Chrome with bundled FP 11.5 release player, the "alternative_new2a" implementation
is actually the fastest in nearly all cases, and has is most readable too, IMHO. This is similar
to the version in patch except it uses const instead of var for the 2 temporary 

I've added the result XML dumps in the "results" directory for my runs. Note the times will
be different to those above, since I changed the benchmark to make it slightly more realistic.
I wrote my own tool to compare 2 XML files (it's written in Go and lives here: https://github.com/maurice/ptcmp
if you want to use it too)
                
> CSSCondition.matchesStyleClient() is slow and creates excessive garbage
> -----------------------------------------------------------------------
>
>                 Key: FLEX-33273
>                 URL: https://issues.apache.org/jira/browse/FLEX-33273
>             Project: Apache Flex
>          Issue Type: Improvement
>          Components: Styles
>    Affects Versions: Adobe Flex SDK 4.1 (Release), Adobe Flex SDK 4.5 (Release), Adobe
Flex SDK 4.5.1 (Release), Adobe Flex SDK 4.6 (Release)
>            Reporter: Maurice Nicholson
>            Assignee: Frédéric THOMAS
>              Labels: patch, performance
>         Attachments: FLEX-33273.patch, PerformanceTest.zip
>
>
> CSSCondition.matchesStyleClient() is called *very* frequently during layout of components
in many different scenarios.
> I've done a lot of profiling of Flex apps and it comes up again and again.
> The current implementation is slow and creates unnecessary garbage (which slows down
the runtime further, since it needs to collect the garbage instead of doing more useful things).
> Here is the current implementation:
> {code}
>     public function matchesStyleClient(object:IAdvancedStyleClient):Boolean
>     {
>         var match:Boolean = false;
>         if (kind == CSSConditionKind.CLASS)
>         {
>             if (object.styleName != null && object.styleName is String)
>             {
>                 // Look for a match in a potential list of styleNames 
>                 var styleNames:Array = object.styleName.split(/\s+/);
>                 for (var i:uint = 0; i < styleNames.length; i++)
>                 {
>                     if (styleNames[i] == value)
>                     {
>                         match = true;
>                         break;
>                     }
>                 }
>             }
>         }
>         else if (kind == CSSConditionKind.ID)
>         {
>             if (object.id == value)
>                 match = true;
>         }
>         else if (kind == CSSConditionKind.PSEUDO)
>         {
>             if (object.matchesCSSState(value))
>                 match = true;
>         }
>         return match;
>     }
> {code}
> Here is what I suggest instead:
> {code}
>     public function matchesStyleClient(object:IAdvancedStyleClient):Boolean
>     {
>         var match:Boolean = false;
>         if (kind == CSSConditionKind.CLASS)
>         {
>             const styleName:String = object.styleName as String;
>             if (styleName)
>             {
>                 // Look for a match in a potential list of styleNames 
>                 FIND:
>                 {
>                     var index:int = styleName.indexOf(value);
>                     if (index == -1)
>                     {
>                         break FIND;
>                     }
>                     if (index != 0 && styleName.charAt(index - 1) != ' ')
>                     {
>                         break FIND;
>                     }
>                     const next:int = index + value.length;
>                     if (next != styleName.length && styleName.charAt(next) !=
' ')
>                     {
>                         break FIND;
>                     }
>                     match = true;
>                 }
>             }
>         }
>         else if (kind == CSSConditionKind.ID)
>         {
>             if (object.id == value)
>                 match = true;
>         }
>         else if (kind == CSSConditionKind.PSEUDO)
>         {
>             if (object.matchesCSSState(value))
>                 match = true;
>         }
>         return match;
>     }
> {code}
> There are obviously more concise ways to express this code, but the above seems to match
the current style more or less.
> Here is the output from a benchmark I created using Grant Skinner's PerformanceTest v2
Beta, comparing the current version and the suggested version:
> {noformat}
> Comparing speed of matching a string in space delimited string. 1000000 loops.
> Test                                                           Old ms   New ms Speedup
 Old mem  New mem  Change
> matchesStyleClient(styleName: "foo", value: "foo")            1006.00   181.00   -82.0
  123.00     0.00  -100.0
> matchesStyleClient(styleName: "foo bar", value: "foo")        2107.00   206.80   -90.2
  115.00     0.00  -100.0
> matchesStyleClient(styleName: "bar foo", value: "foo")        2099.80   232.30   -88.9
  117.00     0.00  -100.0
> matchesStyleClient(styleName: "baz foo bar", value: "foo")    3193.80   251.30   -92.1
  119.00     0.00  -100.0
> matchesStyleClient(styleName: "foobar", value: "foo")         1169.50   192.00   -83.6
  112.00     0.00  -100.0
> matchesStyleClient(styleName: "foofoo bar", value: "foo")     2273.80   191.30   -91.6
  116.00     0.00  -100.0
> matchesStyleClient(styleName: "fo", value: "foo")              918.80   141.00   -84.7
  108.00     0.00  -100.0
> matchesStyleClient(styleName: "fooo", value: "foo")           1052.80   192.00   -81.8
  108.00     0.00  -100.0
> matchesStyleClient(styleName: "2foo bar", value: "foo")       2149.50   205.30   -90.4
  116.00     0.00  -100.0
> matchesStyleClient(styleName: "foo2 bar", value: "foo")       3849.50   190.80   -95.0
  111.00     0.00  -100.0
> matchesStyleClient(styleName: "", value: "foo")               1801.80   141.00   -92.2
  132.00     0.00  -100.0
> {noformat}
> As you can see, the new version doesn't create garbage, and is at least 80% faster in
the above test cases.
> I would be happy to contribute a patch and a FlexUnit test, but I haven't seen any existing
FlexUnit tests in the current source tree, so not sure where to put it.
> Otherwise Mustella seems like a beast to get to know and run, so I will need some guidance
as to what to do if you require new Mustella tests.

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