Hi,
If you need to create 1000 class instances each frame then you have a
flaw in your logic in my opinion.
I have more like a million class instances
For my XPath stuff, and every returned value is put in a variant-like
class. Selecting all nodes on an GB large XML, could even create almost
a billion class instances
I once did a benchmark. It is 10% faster to reuse the class instances
rather than recreating them, my commit log says. And I only implemented
one interface (actually, two interfaces, since IUnknown always gets
pulled in, too. )
Interfaces are not slow because they are are interfaces! When you call
a interface method it has the same costs as a virtual method call! And
the cost for reference counting that interfaces have right now would
be there for ARC as well.
But it is not calling the method, it is calling the wrapper function
That is a additional second method call/jump for every interface method
call.
E.g. _AddRef on TInterfacedObject as an interface, does not call
TInterfacedObject._AddRef, it calls this:
WRPR_$SYSTEM_$$_TINTERFACEDOBJECT_$_IUNKNOWN_$_1_$_SYSTEM$_$TINTERFACEDOBJECT_$__$$__ADDREF$$LONGINT
0000000000424600 4883ef10 sub $0x10,%rdi
0000000000424604 e997f8feff jmpq 0x413ea0
<SYSTEM$_$TINTERFACEDOBJECT_$__$$__ADDREF$$LONGINT>
Bye,
Benito
On 16.02.21 19:48, Sven Barth via fpc-pascal wrote:
Ryan Joseph via fpc-pascal <fpc-pascal@lists.freepascal.org
<mailto:fpc-pascal@lists.freepascal.org>> schrieb am Di., 16. Feb.
2021, 19:21:
>
> There we have:
>
> * slower creation of the class, because each implemented
interface adds another VMT reference to the class which needs to
be initialized.
How bad is this? We need to make a test case we can profile. For
example if you have a game that creates 1000 classes 60 frames per
second. If adding interfaces to the classes hurts this process we
may have a deal breaker.
If you need to create 1000 class instances each frame then you have a
flaw in your logic in my opinion.
> * slow reference counting. Especially if it is thread safe and
exception safe with the implicit exception block
It's a whole other topic but FPC needs opt-in ARC at the language
level for classes. Interfaces are not only slow but then you need
to pass around a reference to the interface instead of the class
you actually care about. It makes no sense to me whatsoever.
Interfaces are not slow because they are are interfaces! When you call
a interface method it has the same costs as a virtual method call! And
the cost for reference counting that interfaces have right now would
be there for ARC as well.
Regards,
Sven
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