Bug in GetRMS() with 2.00/12(gcc/Linux)

From: Joerg.Westphalen@desy.de
Date: Mon Oct 19 1998 - 23:49:24 MEST 

Hi everbody,

after the latest update (to 2.00/12) none of my root programs worked
properly anymore. A few hours of headache let me to the conclusion that
something may be wrong with the GetRMS method of class TH1.

Here is a small program producing wrong results:

// 
// jw 10/98
//
//

#include <TROOT.h>
#include <TApplication.h>
#include <TRint.h>
#include <TF1.h>
#include <TH1.h>

extern void InitGui();
VoidFuncPtr_t initfuncs[] = { InitGui, 0 };


TROOT root("correlation", "CORRELATION", initfuncs);

int main(int argc, char **argv)
{
  int local_argc(1);

  //TApplication* theApp = new TApplication("App", &local_argc, argv);
  TRint *theApp= new TRint("Rint", &local_argc, argv, 0, 0);

  // estimate range for plot
  TF1 *func = new TF1("func","exp(-0.5*((x-11.0)/0.1)^2)");
  TH1F* histo(new TH1F("histo","Histogram of Gluino Condensate",
		       300,10,12));
  histo->FillRandom("func",1024*1024);

  cout << "using data in range " << " " 
       << histo->GetMean() << " " 
       << histo->GetRMS()<< endl;

  printf("%f\n", histo->GetMean());
  printf("%f\n", histo->GetRMS());

  theApp->Run();

  delete theApp;

  return 0 ;
}


Compiling this (with gcc or egcs) and executing results in:

[...]
  *******************************************
  *                                         *
  *        W E L C O M E  to  R O O T       *
  *                                         *
  *   Version   2.00/12    9 October 1998   *
  *                                         *
  *  You are welcome to visit our Web site  *
  *          http://root.cern.ch            *
  *                                         *
  *******************************************

CINT/ROOT C/C++ Interpreter version 5.13.75, Sep 23 1998
Type ? for help. Commands must be C++ statements.
Enclose multiple statements between { }.


using data in range  28104 1.04858e+06
28104.000000                         <---!!!!!!!!!!!!!
1048576.000000
root [0] printf("%f\n", histo->GetRMS());
0.099994                             <---!!!!!!!!!!!!!
root [1] 

When drawing (histo->Draw()) also RMS=0.0999939 shows up.

Whats wrong with my program, or is this is a bug in root ?
Is this a local problem with our installation here ?

Bye,

Joerg Westphalen

PS. In my original programs i am using Fill(x,w), not FillRandom(),
producing the same problem.


-- 
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Joerg Westphalen                 Email: Joerg.Westphalen@desy.de 
DESY - Theorie -                 Julius-Brecht-Str. 7  
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Tel: 040-8998-3605 (buero)       Tel: 040-8078007 (privat)  
Fax: 040-8994-3605   
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