Re: ROOT version 5.19/02: Update to Release notes with new module RGLITE

Sebastien,

I am posting below a mail from Axel to the Architects Forum describing the motivations for the new Reflex API. Axel will probably post more information once he will back online.

Rene Brun

here are the reasons for changing the Reflex API in a backward incompatible way:

The current version of Reflex makes the new CINT about 15 times slower than the
old one. Fixing this requires a few backward incompatible modifications of the
Reflex API. The following issues will be addressed, too:

• redesign with thread safety in mind (was not taken into account before)
• platform independent, very efficient containers instead of searches through vectors
• cleaner API; previous design philosophy was "duplicate as much as possible for ease of access", new one: "reduce duplication for ease of understanding and maintenance". Example: before, we had Size(), At(), Begin(), End(), RBegin(), REnd() for every container, and we had member access through Type and Scope. Now Reflex exposes the container itself (i.e. 6 -> 1 function) and members are only accessible through their declaring scope (i.e. reduce API by factor 2). Brings Reflex::Type from 173 to 77 methods, i.e. down to 40%.
• reduce the number of layers in call chains to speed up calls. Example: before, Type::Name() for e.g. "void* f(int& i, float a[4])" involved approx 14 string copies (which means malloc, strlen, memcpy, free). Now it's down to 0.

The backward incompatible API changes will show up in ROOT's trunk soon. Even afterwards, during the coming few months, a few API changes are expected, but I will try to make those later changes backward compatible.

I will produce an overview of the API changes (old vs. new) once they have been defined; most of them are trivial changes of type search-and-replace.

Cheers, Axel.

Sebastien Binet wrote:
> Bonjour Rene,
>
> On Thursday 13 March 2008 09:15:29 Rene Brun wrote:
>
>> In the 5.19/02 announcement, we forgot the description of the new RGLite
>> plug-in by Anar Manafov.
>> We have now added the description of RGLITE to the release notes:
>> http://root.cern.ch/root/Version519.news.html
>>
>
> going through the release notes, my attention was caught by:
> """
> Reflex.Several fundamental enhancements are available for Reflex.
> This is a precursor to the API changes already announced for the near future
> """
>
> Where were these api changes announced ? and where can I get a rough idea of
> their inpact, rationale, doc,... ?
>
> Thanks.
>
> A bientot,
> Sebastien.
>
Received on Thu Mar 13 2008 - 18:02:19 CET