apple2freak{at}gmail.com wrote:
> On Mar 5, 3:18 pm, mdj  wrote:
>> On Mar 5, 4:07 pm, apple2fr...{at}gmail.com wrote:

>> The reduction in code complexity by using automatic collection however
>> is a huge benefit to productivity. Consider also that an piece of code
>> doing it's own collection manually will run more slowly than code that
>> doesn't, and delegates it to another process that runs in parallel.
>>
> There are pros & cons to both ways of doing it.  Since Java doesn't
> specify exactly when garbage collection may occur, this can cause
> execution delays at inconvenient times -- something easily programmed
> around in C++.  Also, as I mentioned earlier, the C++ Boost library
> contains a robust garbage collector if that is your thing.

Does Java at least have a way to signal that "now would be a convenient
time to garbage collect"?  That would go a long way toward eliminating
inconvenient pauses.

>> Also consider the advantages of being able to make optimisation
>> decisions at runtime vs. compile time. Something your compiler decided
>> to inline might run beautifully on your machine, but cache-thrash
>> really badly on your customers smaller system.
>>
> This is true in theory; however in practice I have yet to experience
> any Java program running more quickly (or with less memory) than an
> equivalent C++ program on any platform.

This kind of evaluation is one that needs to be done, just to provide
some objective accountability for the design decision.

I have created lots of examples where dynamic optimization can produce
a considerable advantage.  I know of two actual experiments in which
a machine re-wrote its own object code dynamically based on timer-sample
profile data, and achieved a net improvement of several percent even
*including* the additional overhead of profiling, analysis, and code
re-generation!  These were very simple optimizers with tiny "toolkits"
of patterns.

Of course, the longer the program ran, the less the contribution of the
overhead and the greater the net improvement.

-michael

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