http://www.caughtbyjava.com Just another Technology Blog Sun, 20 Jun 2010 10:35:17 -0500 http://wordpress.org/?v=2.9.2 hourly 1 http://www.caughtbyjava.com/new-findings-for-hashtable-vs-synchronized-map-vs-concurrenthashmap-2/comment-page-1/#comment-902 Asim Sun, 20 Jun 2010 10:35:17 +0000 http://www.caughtbyjava.com/?p=186#comment-902 Thanks Peter for your suggestions.

I will try again keeping your suggestions in mind and post my findings. I know people would have done that already but I dont want to keep this post incomplete.
I will try again keeping your suggestions in mind and post my findings. I know people would have done that already but I dont want to keep this post incomplete.]]> http://www.caughtbyjava.com/new-findings-for-hashtable-vs-synchronized-map-vs-concurrenthashmap-2/comment-page-1/#comment-901 Peter Lawrey Sun, 20 Jun 2010 07:15:03 +0000 http://www.caughtbyjava.com/?p=186#comment-901 Also, you should compare your timings with just using a single thread. If you cannot do more work with multiple threads than a single thread, you don't have a good example for multi-threaded code. (In which case you wouldn't use multiple threads) http://www.caughtbyjava.com/new-findings-for-hashtable-vs-synchronized-map-vs-concurrenthashmap-2/comment-page-1/#comment-900 Peter Lawrey Sun, 20 Jun 2010 06:44:26 +0000 http://www.caughtbyjava.com/?p=186#comment-900 First impression, if you are going to give a benchmark to someone, I suggest you use nested classes, this way there is only one file to deal with. ;)

The key problem you have here is that your testing framwork is much more heavy weight than the thing you are testing. This means your results are more of an indication as to how your framework is perfoming than the thing you are testing.

Perhaps the most important lessons here are that<br />- when optimising, start with the most expensive operation, don't guess, use a profiler and your judgement after that.<br />- whatever you do with the Map is far more likely to be important the cost of the Map itself, for any real application.

If you were to optimise it, I would suggest<br />- using a thread pool which is the size of the number of cores you have.<br />- make each task in the thread pool perform a singiciant piece of work, one put() is likely to be trivial compared to the cost of even adding a task to a thread pool. Certainly trivial compared with starting a new thread. Try 1000 puts or more.<br />- Use System.nanoTime for more accurate benchmarks. Using Date is not as expensive as Calendar but its one of the most expensive and least accurate ways to benchmark.<br />- Don't use new objects for keys or values. I would pre-generate them all and only time the start and the end (with nanoTime), not the timing for each element as you have done. Taking the System.currentTimeMillis() (which Date does) can be more expensive than put().

The key problem you have here is that your testing framwork is much more heavy weight than the thing you are testing. This means your results are more of an indication as to how your framework is perfoming than the thing you are testing.

Perhaps the most important lessons here are that
- when optimising, start with the most expensive operation, don’t guess, use a profiler and your judgement after that.
- whatever you do with the Map is far more likely to be important the cost of the Map itself, for any real application.

If you were to optimise it, I would suggest
- using a thread pool which is the size of the number of cores you have.
- make each task in the thread pool perform a singiciant piece of work, one put() is likely to be trivial compared to the cost of even adding a task to a thread pool. Certainly trivial compared with starting a new thread. Try 1000 puts or more.
- Use System.nanoTime for more accurate benchmarks. Using Date is not as expensive as Calendar but its one of the most expensive and least accurate ways to benchmark.
- Don’t use new objects for keys or values. I would pre-generate them all and only time the start and the end (with nanoTime), not the timing for each element as you have done. Taking the System.currentTimeMillis() (which Date does) can be more expensive than put().]]> http://www.caughtbyjava.com/intellij-idea-9-released/comment-page-1/#comment-896 Abraham Robinson Wed, 16 Jun 2010 05:30:05 +0000 http://www.caughtbyjava.com/?p=175#comment-896 Really interesting reading, great job man ! Feel free to comment on my blog, I was solving similar problem. http://www.caughtbyjava.com/search-pagination-design-using-hibernate/comment-page-1/#comment-419 F. James Sensenbrenner Sat, 02 Jan 2010 16:48:07 +0000 http://www.caughtbyjava.com/?p=147#comment-419 I really like this blog. Please continue the great work. Regards!!! http://www.caughtbyjava.com/intellij-idea-9-released/comment-page-1/#comment-339 Robert Nicholson Mon, 28 Dec 2009 10:40:41 +0000 http://www.caughtbyjava.com/?p=175#comment-339 Be careful with the new behavior they have when u remove a module from your project because it wants to delete all it's code and remove it from CVS http://www.caughtbyjava.com/search-pagination-design-using-hibernate/comment-page-1/#comment-322 Ignacio Coloma Tue, 22 Dec 2009 16:03:10 +0000 http://www.caughtbyjava.com/?p=147#comment-322 Deeper insight about your first approach can be obtained here:

http://code.google.com/appengine/articles/paging.html

It is slightly outdated, but the main ideas still can be applied to your environment. This is more or less what is done by Twitter to solve pagination on their Ajax API.

About the third one, there are "endless page" widgets everywhere.
http://code.google.com/appengine/articles/paging.html

It is slightly outdated, but the main ideas still can be applied to your environment. This is more or less what is done by Twitter to solve pagination on their Ajax API.

About the third one, there are “endless page” widgets everywhere.]]> http://www.caughtbyjava.com/knowing-cache-and-java-cache-system/comment-page-1/#comment-98 Kalpesh Sun, 04 Oct 2009 16:49:48 +0000 http://www.caughtbyjava.com/?p=112#comment-98 Good article. <br />Need to dig in more so that I can implement in my application Need to dig in more so that I can implement in my application]]> http://www.caughtbyjava.com/java-implementation-of-strategy-design-pattern/comment-page-1/#comment-97 Romase Sun, 04 Oct 2009 03:03:44 +0000 http://www.caughtbyjava.com/?p=131#comment-97 site best http://www.caughtbyjava.com/java-implementation-of-strategy-design-pattern/comment-page-1/#comment-96 Globals Sat, 03 Oct 2009 04:41:19 +0000 http://www.caughtbyjava.com/?p=131#comment-96 all good things