Rene Brun wrote:
>
> Hi Nick, Hi Jeff,
> As both of you know, we have introduced in 2.22 new versions of the
> classes
> TVector3 and TLorentzVector. We had several iterations with the FNAL
> team
> supporting ZOOM & CLHEP. We finally agreed on an implementation that
> you can find in 2.22/09 released yesterday.
>
> Since both of you do not specify which version of Root you are referring
> to,
> I am not sure that you are talking of the same thing.
> During the discussions with FNAL, we investigated the point if
> TLorentzVector
> should derive from TVector3 or not. There are pros/cons with the two
> approaches.
>
> The idea was to converge with the CLHEP versions of LorentzVector.
> We are convinced that for frequently used classes such as
> TLorentzVector,
> it is not a good idea that everybody implements his own version.
> We had many comments from users that a convergence should be possible
> and it is a very frustating situation to see different implementations.
>
> The current implementation in 2.22/09 does not derive from TVector3, but
> all the functionality from TVector3 is available in TLorentzVector.
>
> I would like to understand what are precisely the criticisms with the
> current implementation.
> Jeff, please give more details on the problems.
> Nick, indicate the strong points of your version (possibly weak
> points)
> compared to TlorentzVector.
>
> This class is fully documented at URL:
> http://root.cern.ch/root/html/TLorentzVector.html
>
> I hope to have some input from FNAL ZOOM/CLHEP teams on this point.
>
> Rene Brun
>
Hi Rene,
When I looked into this stuff I did this for a pre-2.22/08 version of ROOT;
I will pick up the new 2.22/09 and have a look at it again and compare with
our home-grown stuff.
In case there is some functionality of Ali4Vector & co. which I think is needed
and which is lacking in TLorentzVector & co. I will let you know.
I don't understand the argument why one could not support 2 versions
(i.e. one deriving from 3-vector and one not) so that one can profit from
all the pros of the both approaches.
Cheers,
Nick.
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