Java/Profiling - Revision history

Admin: /* References */

2017-03-20T02:42:19Z

References

← Older revision		Revision as of 02:42, 20 March 2017
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	For the recursive backtracking method, this did not reveal anything about where the real time was being spent.		For the recursive backtracking method, this did not reveal anything about where the real time was being spent.

			=Timing Java Code=

			See [[Java/Timing]]

	=References=		=References=

2017-03-19T07:03:59Z

JIP: Java Interactive Profiler

← Older revision		Revision as of 07:03, 19 March 2017
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	This is a project available on sourceforge: http://jiprof.sourceforge.net/		This is a project available on sourceforge: http://jiprof.sourceforge.net/

	~~Once you download~~ the source code for the project~~, you will see~~ a profile folder ~~(among other things) that contains~~ a profile.jar ~~file~~. This ~~profile.~~jar file contains ~~all the code~~ you need to profile your program with the JIP.		==Instructions==

			Start by downloading the source code for the project.

			Look in that directory for a folder called <code>profile/</code>. Look in that folder for a Jar file called <code>profile.jar</code>. This jar file contains everything you need to profile your program with the JIP.

			Store this Jar file somewhere easy to find, as you will be pointing the Java executable to the Jar file when you run the program that you are profiling.

			==Running Java with JIP==

	When you run Java, pass the <code>-javaagent</code> flag, and the location of profile.jar:		When you run Java, pass the <code>-javaagent</code> flag, and the location of profile.jar:
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	==Example JIP Output==		==Example JIP Output==

	Here is example output for a Java N queens problem solution:		The JIP will create an output file in <code>profile.txt</code>. Here is example output for a Java N queens problem solution:

	<pre>		<pre>

2017-03-19T07:02:00Z

=Using JIP Output to Improve Code

← Older revision		Revision as of 07:02, 19 March 2017
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	</pre>		</pre>

	===Using JIP Output to Improve Code==		==Using JIP Output to Improve Code==

	We can use the output of the JIP profiling tool to make a major improvement to our N queens problem implementation. Take a look at the last table, which contains quite a bit of information about where our program is spending all its time:		We can use the output of the JIP profiling tool to make a major improvement to our N queens problem implementation. Take a look at the last table, which contains quite a bit of information about where our program is spending all its time:
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	The total time spent in the legalRows class dropped drastically, and now the explore method is the most expensive method called.		The total time spent in the legalRows class dropped drastically, and now the explore method is the most expensive method called.


	=Hprof=		=Hprof=

2017-03-19T07:01:49Z

2017-03-19T07:01:13Z

JP: Java Interactive Profiler

← Older revision		Revision as of 07:01, 19 March 2017
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	So much for that idea.		So much for that idea.

	=JP: Java Interactive Profiler=		=JIP: Java Interactive Profiler=

	The Java interactive profiler is covered here: http://confluence.concord.org/display/CCTR/attachments/15911/1574.pdf		The Java interactive profiler is covered here: http://confluence.concord.org/display/CCTR/attachments/15911/1574.pdf

2017-03-19T07:00:57Z

Example JIP Output and Improvements

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 This creates the file <code>profile.txt</code>, which provides an excellent breakdown of what amount of time was spent in which function calls, from the highest level of the program down to the lowest level.
-==Example JIP Output and Improvements==
+==Example JIP Output==
 Here is example output for a Java N queens problem solution:
@@ Line 315: / Line 315: @@
       0.0    0.0  Board:choose
       0.0    0.0  Board:size
 +--------------------------------------+

2017-03-19T06:59:34Z

Example JIP Output and Improvements

← Older revision		Revision as of 06:59, 19 March 2017
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	</pre>		</pre>

	You'll notice that a ~~huge~~ amount of time is spent getting the size of the board, and in legalRows, which is a method that calls the size() method many, many times.		You'll notice that a HUGE amount of time is spent getting the size of the board, and in legalRows, which is a method that calls the size() method many, many times.

	It turns out that this ~~simple implementation~~ detail ~~is a HUGE bottleneck for the code~~ - ~~the fact that, from the board class, we are~~ calling ~~the~~ size() ~~method~~ instead of ~~simply accessing~~ the ~~private variable storing the board size~~. ~~This~~ is a ~~seemingly trivial detail, but~~ check out the ~~affect of completely eliminating~~ size() ~~calls from~~ the ~~Java file~~:		It turns out that this seemingly trivial detail - calling <code>size()</code> instead of <code>this.size</code> - is a major bottleneck for the code. It is quite amazing what a big affect this has: check out the same exact problem, but with all calls to size() in the Board class eliminated:

	<pre>		<pre>

2017-03-19T06:58:01Z

Example JIP Output

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 This creates the file <code>profile.txt</code>, which provides an excellent breakdown of what amount of time was spent in which function calls, from the highest level of the program down to the lowest level.
-==Example JIP Output==
+==Example JIP Output and Improvements==
 Here is example output for a Java N queens problem solution:
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       0.1    0.0  SolutionSaver:nSolutions
 </pre>
 =Java Mission Control=

2017-03-19T06:44:48Z

Java Mission Control

2017-03-19T06:03:28Z

Examining heap dumps with jhat

← Older revision		Revision as of 06:03, 19 March 2017
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	This will create a very large output file in java.hprof.txt.		This will create a very large output file in java.hprof.txt.

			Now examine it with the jhat utility:

			<pre>
			$ jhat java.hprof.txt
			Reading from java.hprof.txt...
			java.io.IOException: Version string not recognized at byte 18
			at com.sun.tools.hat.internal.parser.HprofReader.readVersionHeader(HprofReader.java:390)
			at com.sun.tools.hat.internal.parser.HprofReader.read(HprofReader.java:175)
			at com.sun.tools.hat.internal.parser.Reader.readFile(Reader.java:92)
			at com.sun.tools.hat.Main.main(Main.java:159)
			</pre>

			So much for that idea.

	=Java Mission Control=		=Java Mission Control=