[ROOT] precision loss in TTree::Scan *selection argument?

From: Rene Wilhelm (wilhelm@ripe.net)
Date: Tue Apr 10 2001 - 02:28:18 MEST 

Hi,

I'm trying to locate specific events in our data set, but somehow a
strict equality test in TTree::Scan() doesn't find them. Could it be
there's a loss of precision in the decoding of the *selection
character string?

Following snapshot illustrates my problem:

  root [1] T.Scan("PacketId:TargetId", "PacketId==985011665")                
  ************************************
  *    Row   *  PacketId *  TargetId *
  ************************************
  *    42548 * 985011648 *        26 *
  ************************************
  ==> 1 selected entry

  root [2] T.Scan("PacketId:TargetId", "TargetId==16 && PacketId==985011665")
  ************************************
  *    Row   *  PacketId *  TargetId *
  ************************************
  ************************************
  ==> 0 selected entries

  root [3] T.Scan("PacketId:TargetId", "TargetId==16 && PacketId>985011600 &&
  PacketId <985011700")
  ************************************
  *    Row   *  PacketId *  TargetId *
  ************************************
  *    42529 * 985011626 *        16 *
  *    42561 * 985011665 *        16 *
  *    42594 * 985011703 *        16 *
  ************************************
  ==> 3 selected entries
  

First command returns false match (985011648 != 985011665), second command
with additional boundary condition suggests the requested event does not exist,
but the third command, with less strict boundary conditions shows it *does*
exist (row 42561). Any idea what's going on?

This is with ROOT version 2.25/03.

Kind regards,

-- Rene


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Rene Wilhelm                    RIPE Network Coordination Centre
Email: wilhelm@ripe.net         Test Traffic Measurements
Phone: +31 20 535 4417          Amsterdam, the Netherlands
Fax:   +31 20 535 4445          http://www.ripe.net/test-traffic/
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