topic Re: Performance issue with global constants? in Application Development and Automation Discussions

Performance issue with global constants?

andreas-de — Fri, 08 Jun 2018 10:43:27 GMT

Hello,

I prefer to define constants as attributes in a class interface for cross program usage. Now, someone said, global constants have an negative performance issue. Argumentation is something like "The constant value needs to be copied from global stack to local program stack".

Looking at 'Declaration of Data Types and Constants' (SAP ABAP docu) I think it should be ok like I usual do.

Can you confirm performance issues with global ABAP OO constants? Is this a real issue which the end user will realize at a normal transcation? Or is this more a academic topic?

Thanks in advance

Re: Performance issue with global constants?

holger_janz — Fri, 08 Jun 2018 11:47:57 GMT

No, there aren't performance issues with global constants. #fairytale

Re: Performance issue with global constants?

pokrakam — Fri, 08 Jun 2018 13:19:56 GMT

This is possibly an issue with loading a static class into the internal session memory, which - unlike instances - is not unloaded by the garbage collector. I think this may be what your colleague might be referring to.

This is one argument for using interface vs class constants, as interfaces contain no executable code and interface constants are (probably) evaluated at compile time. Personally I use interface constants as well for this reason.

Re: Performance issue with global constants?

retired_member — Fri, 08 Jun 2018 16:00:26 GMT

https://help.sap.com/http.svc/rc/abapdocu_752_index_htm/7.52/en-US/index.htm?file=abenpxa_glosry.htm

Re: Performance issue with global constants?

pokrakam — Fri, 08 Jun 2018 20:20:42 GMT

...which is exactly the bit I'm unsure about: Since interfaces have no executable code, are they considered bytecode or processed in their entirety at compile-time for scenarios such as this? It's theoretically possible, but, ABAP being ABAP, theory means little 🙂

Re: Performance issue with global constants?

Jelena_Perfiljeva — Fri, 08 Jun 2018 22:04:55 GMT

I guess documentation is due for another update. 🙂

But seriously - are we even talking any significant potential performance impact here?

Re: Performance issue with global constants?

sharanjee_186716 — Sat, 09 Jun 2018 03:41:04 GMT

Use Interface Constants instead of Class. There is no performance issues with global constant.

Re: Performance issue with global constants?

pokrakam — Sat, 09 Jun 2018 06:06:17 GMT

Could have a significant impact for large scale compute-intensive applications such as cosmological dark matter distribution modelling, or playing chess against another computer.

In other words, mostly academic.

Re: Performance issue with global constants?

retired_member — Sun, 10 Jun 2018 13:45:14 GMT

PXA also buffers shared resources like the values of constants.

Re: Performance issue with global constants?

retired_member — Sun, 10 Jun 2018 13:47:46 GMT

But classes allow unit tests. Can make sense even for constants (checking values against external ressources).