Re: [WebMacro-user] Optimising Variable to reduce instantiation overhead

[Alex Twisleton-Wykeham-F. <al...@fi...>]

On Mon 13 March 2006 12:34, Endre St=F8lsvik wrote:
> On Sun, 12 Mar 2006, Alex Twisleton-Wykeham-Fiennes wrote:
> | All,
> |
> | more performance tweaks, this one to the org.webmacro.engine.Variable
> | class.
>
> Excellent performance tuneup you're into, Alex!
>
> | - made the getVariableName() method check to see if _vname has been
> | initialised, and if not then build the name before returning it.  This =
is
> | now synchronized as it changes the state of the object.
>
> So?

If you don't synchronize then you could potentially have two threads modify=
ing=20
the state of the Object simultaneously.  In this situation it is not the en=
d=20
of the world, because the generation of the result is a) not that expensive=
,=20
and b) not dependent on other mutable properties, but I find it best to app=
ly=20
thread-safe approaches to everything that changes state and then remove the=
m=20
if profiling shows it to be a problem.  Much better to start safe and then=
=20
remove redundant safety when required than to start unsafe and try and make=
=20
things safe when a weird multi-threading bug occurs...

> Is it shared across threads?

I'd have to double check this one.  It's a bit of a twisty turny passage of=
=20
Macro inheritance and it isn't necessarily obvious...

Alex

ps synchronizing is really not the overhead that it used to be in older JVM=
s=20
and it *really* makes your life easier to not have any multi-threading=20
bugs...