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Re: Static Method performance
Mayank,
When I run your test, here are the results that I get:
-------------------------------------
java Test1
Non Static call - 1116
Static call - 1046
Process Test1 finished
-------------------------------------
This is what I would expect; namely, that a static method is the same or a
little faster than a non-static call. You have to be very careful when you run
Java benchmarks since it is easy to get spurious results. This occurs for
various reasons; e.g., garbage collection kicking in. It is always best to run
a series of tests and discard the first test in each series.
The basic difference between these two types of methods is that non-static
methods have access to the instance data of a class while non-static methods do
not.
Whether to use a static or a non-static method should be based on what data you
need to access. If the calculations need to access data within a particular
class instance, then using a non-static method would be appropriate. If all of
the data is provided through the method parameters, then a static method would
work.
Cynthia Jeness
Mayank Aggarwal wrote:
> I did a small test-
> The following code calls a static and a non-static method which effectively
> do the same thing - some time consuming processing.
> Run the code and you would see the static calls takes almost the double time
> than the non-static call.
>
> Any thoughts??
>
> So if we maintain a pool of objects and let the calling party get an
> instance from the pool and make a call--i guess that would be faster.
>
> Thanks
> Mayank
> --------------------------------------------------------
> public class Test1
> {
> public static void main(String[] args)
> {
> long l1 = System.currentTimeMillis();
>
> Test2 t = new Test2();
> t.Met2();
>
> long l2 = System.currentTimeMillis();
>
> System.out.print("Non Static call - ");
> System.out.println(l2-l1);
>
> l1 = System.currentTimeMillis();
>
> Test2.Met1();
> l2 = System.currentTimeMillis();
>
> System.out.print("Static call - ");
> System.out.println(l2-l1);
> }
>
> }
>
> class Test2
> {
> public static void Met1()
> {
> for(int i=0;i<10000;i++)
> {
> for(int j=0;j<10000;j++);
> }
> }
>
> public void Met2()
> {
>
> for(int i=0;i<10000;i++)
> {
> for(int j=0;j<10000;j++);
> }
> }
>
> }
> --------------------------------------------------------------
> ----- Original Message -----
> From: "Curt Smith" <chsmith@speakeasy.net>
> To: <ajug-members@www.ajug.org>
> Cc: <ajug-members@www.ajug.org>
> Sent: Wednesday, February 27, 2002 2:58 PM
> Subject: Re: Static Method performance
>
> >
> > > Say there are 500 objects which have to use a certain method X (
> exampled
> > > below).
> > > If i make X as static then 499 objects would have to queue up for access
> to
> > > the method,
> >
> >
> > Note that static does not mean synchronized.
> >
> > Your example would allow all threads to access your data[] array
> > concurrently. This is ok, even safe if your data does not change
> > at run time. Even if it does change, there's several operations
> > that the VM assures to be atomic. Not enough space here for
> > that.
> >
> > If data[] is big or expensive to create, this is a perfect candidate
> > for a static method and members. You can still have a synchronized
> > mutator to change out the whole data array or just an index, leveraging
> > atomicity of a variable equate operation. But your business data
> > may have more state that all needs to be consistant for this simplistic
> > discussion about what's atomic and safe in a concurrent environment.
> >
> > re: the performance advantage, my guess is that the 15% perf advantage
> > is entirely due to new object () and garbage collection for the
> > non-static test case. If the same object's method was being called
> > and vs creating a new object each time,
> > I'd be surprised that some vendor's JIT wouldn't be able to remove any
> perf.
> > difference. TBD
> >
> > curt
> >
> >
> > while if i make X an instance variable then each of 500 objects
> > > would have their own copy of the X's object and hence a copy of X.
> > >
> > > public class Y
> > > {
> > > String[] data = new String[100];
> > >
> > > public String[] X(int i)
> > > {
> > > return (data[i],data[i+1].....data[i+10]);
> > > }
> > >
> > > }
> > >
> > > I understand that if i make X as static then data would also be a static
> > > variable.
> > >
> > > Hope i have been able to express my question correctly.
> > >
> > > Thanks
> > > Mayank
> > >
> > > ----- Original Message -----
> > > From: "Brian Lee" <brian_a_lee@hotmail.com>
> > > To: <aggarwalmayank@hotmail.com>; <ajug-members@www.ajug.org>
> > > Sent: Wednesday, February 27, 2002 1:34 PM
> > > Subject: Re: Static Method performance
> > >
> > >
> > >
> > >>I've seen about a 15% increase in performance between the same method
> > >>
> > > static and non-static. The test is pretty basic (do this 1000000 times
> and
> > > time it) so I don't have real-world data.
> > >
> > >>The only downside I've experienced with static methods is that if your
> > >>
> > > class is implementing an interface, the interface defined methods can't
> be
> > > static.
> > >
> > >>Other than this, I make as many methods as possible static (and final)
> for
> > >>
> > > performance reasons. Since most of the code I write doesn't go into a
> > > published API, I declare final and then change it if extending becomes
> > > necessary.
> > >
> > >>BAL
> > >>
> > >>
> > >>>From: "Mayank Aggarwal" <aggarwalmayank@hotmail.com>
> > >>>To: <ajug-members@www.ajug.org>
> > >>>Subject: Static Method performance
> > >>>Date: Wed, 27 Feb 2002 13:02:57 -0500
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> > >>>How does static method affect performance in Java?
> > >>>
> > >>>I understand that all the method variables are created on Stack and
> hence
> > >>>
> > > each calling party gets its own stack of variables, hence there should
> not
> > > be problems of concurrency as long as only method local variables are
> > > manipulated.
> > >
> > >>>What other reasons are there for not using a static methods ?
> > >>>
> > >>>
> > >>>Thanks
> > >>>Mayank
> > >>>
> > >>
> > >>
> > >>
> > >
> >
> >
> > --
> >
> > Curt Smith
> > chsmith@speakeasy.net
> > (w) 404-463-0973
> > (h) 404-294-6686
> >
> >
> >
> >