TRandom3 problem setting seed

[Javier_Galan]

I am a bit confused, how I should set the random generator seed? I thought I should get back the seed is 3, but I always get 624.

I get the following in a root interactive session:

   ------------------------------------------------------------------
  | Welcome to ROOT 6.26/06                        https://root.cern |
  | (c) 1995-2021, The ROOT Team; conception: R. Brun, F. Rademakers |
  | Built for linuxx8664gcc on Oct 11 2022, 13:18:00                 |
  | From heads/latest-stable@274b476a                                |
  | With c++ (Debian 8.3.0-6) 8.3.0                                  |
  | Try '.help', '.demo', '.license', '.credits', '.quit'/'.q'       |
   ------------------------------------------------------------------

root [0] TRandom3 *rnd = new TRandom3(3);
root [1] rnd->GetSeed()
(unsigned int) 624
root [2] rnd->SetSeed(3)
root [3] rnd->GetSeed()
(unsigned int) 624
root [4] 

[Wile_E_Coyote]

Tiny number of electrons produce by TrackSrim

The “624” seed value is a TRandom3::GetSeed incompatibility introduced in ROOT 6.24/00. You can get the backward compatible behavior when you use, e.g.: gRandom->TRandom::GetSeed()

[Javier_Galan]

Ok, if I use gRandom->TRandom::GetSeed() I recover back the good seed. But I do not understand why fRandom->GetSeed() just does not return the good seed value, since it is the most intuitive way.