System.out calls

[Bruce Lee]

Do frequent System.out calls hamper performance?

 

[hiwa]

Bruce Lee ã®ãƒ¡ãƒƒã‚»ãƒ¼ã‚¸:

Do frequent System.out calls hamper performance?

Yes, even a single one does. You should avoid the use
of System.out at all cost.

Jokes aside, what kind of application are you talking
about?

 

[Roedy Green]

Do frequent System.out calls hamper performance?

It is better to block up a string then output it all at once.

 

[Ross Bamford]

Do frequent System.out calls hamper performance?

Well, System.out is synchronized, so yes, frequent calls will cause some
bottlenecking. If you really overuse it, it's easy to destroy any benefits
you gain from multithreading. And output in general is _slow_ compared to
memory operations.

As Roedy (rightly) advises, it's best to store up output for a single
System.out call. One common way is to have a buffered writer with manual
flush, backed by System.out and only flushed every so often.

 

[Chris Uppal]

[...] And output in general is _slow_ compared to
memory operations.

And output to a TTY (in Unix) or to a Windows "console" can be /very/ slow even
compared to I/O in general.

-- chris

 

[Thomas G. Marshall]

Ross Bamford coughed up:

Well, System.out is synchronized, so yes, frequent calls will cause
some bottlenecking.

*ONLY* if there are different threads attempting the system.out.{whatever}at
the same time! It is a slow beast anyway, simply because it is i/o, but you
may be misleading the newbie a little. A synchronized method doesn't block
anything other than what it is synchronizing on, in this case all the
java.io.PrintStream methods synchronize on their own instances.

 

[Ross Bamford]

Ross Bamford coughed up:

*ONLY* if there are different threads attempting the
system.out.{whatever}at
the same time! It is a slow beast anyway, simply because it is i/o, but
you
may be misleading the newbie a little. A synchronized method doesn't
block
anything other than what it is synchronizing on, in this case all the
java.io.PrintStream methods synchronize on their own instances.

True, I should have been clearer that this applies specifically to
multithreaded programs, where System.out is called from different threads.
The time taken to actually obtain a (previously open, obviously)
synchronization lock is vanishingly small, so it's not an _automatic_
performance hit (that comes from the IO )

Apologies for the confusion.

 

[Bruce Lee]

cheers

 

[Thomas G. Marshall]

Chris Uppal coughed up:

[...] And output in general is _slow_ compared to
memory operations.

And output to a TTY (in Unix) or to a Windows "console" can be /very/ slow
even compared to I/O in general.

-- chris

Coding from your 110 baud teletype again?