Re: DC and BFS tracking

From: Kris Hagel (hagel@comp.tamu.edu)
Date: Wed Apr 03 2002 - 10:05:37 EST

  • Next message: Flemming Videbaek: "RH 7.2"

    Let me coment on the track IDs since I implemented the track id as an int
    cast to the memory location of the track (ie the pointer).  I was working on
    that in the development stage and in the beginning the ids were serial
    numbers that started with 1, 2, 3, ...  Unfortunately, that was done at the
    time both in the DC and in the TPC, so I sometimes had different tracks with
    identical id's.  I therefore had the idea at the time that they could not
    both be in the same memory location (not taking into account if a TPC track
    was deleted and another DC track created at the memory location), so I could
    guarantee that the IDs generated using the memory location cast to an int
    would be unique.
    
    I have lost track of how it is done in the TPCs these days, but if I was to
    do it over again, I would use the new root facility (I forget what it is
    called for the moment) which gives you a number which is guaranteed to be
    unique to generate the track ids.  It is somehow based on the number of
    nanoseconds since the epoch and I guess the idea is that you cant ask for a
    number within a nano second to get the same one.  I looked through the code
    and it is not obvious how it works, but they say it does.
    
    Anyway, a short history of track ids for your cultural enrichment.
    
    Kris
    
    Djamel Ouerdane wrote:
    
    > Hi Flemming et al,
    >
    > After having read your message, I realized that I misunderstood the way
    > the track IDs were set. I would have expected that they are set like for
    > the TPC tracks. Casting the pointer to an integer gives a relatively big
    > number that at first glance looks like an uninitialized variable. Sorry
    > for the confusion. I'm gonna correct it.
    >
    > Djam
    >
    > --
    > Djamel Ouerdane ------------------------------------------o
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