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Re: Problems with integer FairTrackPar charge [message #9429 is a reply to message #9428] Mon, 21 September 2009 14:46 Go to previous messageGo to previous message
Mohammad Al-Turany is currently offline  Mohammad Al-Turany
Messages: 518
Registered: April 2004
Location: GSI, Germany
first-grade participant
From: *gsi.de
Hi,

I manage to repruduce the crash on Debian Etch 32, and it is in the FairGeaneUtil:

Quote:

Program received signal SIGFPE, Arithmetic exception.
[Switching to Thread -1229228352 (LWP 18037)]
0xb3fe5bc1 in FairGeaneUtil::FromSDToMars (this=0xbfc1e124, PC=0xbfc1e0d8,
RC=0xbfc1dfd0, H=0xbfc1e0f0, CH=0, SP1=1, DJ1=0xbfc1e6a0, DK1=0xbfc1e6b8,
PD=0xbfc1e108, RD=@0xbfc1deb0)
at /misc/turany/svn/pandaroot/trackbase/FairGeaneUtil.cxx:1485
1485 M65[0][0] = - SPU*PM2*PC[1]/(CH*PVW);


So as you can see it is a division by zero! and this comes from the CH = 0 which comes in this case from FairTrackParP:

fq= int (P * fQp);

As Stefano suggested replacing this with

fq = (int)TMath::Sign(1.0, fQp)

Solves the problem. I tried to print out the values for these two functions using 32 and 64 bit mashines:

on 32-bit:

Quote:

FairTrackParP::FairTrackParP fq = (int)TMath::Sign(1.0, fQp); P =2.046 fQp = -0.4887 fq = -1
FairTrackParP::FairTrackParP fq= int (P * fQp); P =2.046 fQp = -0.4887 fq = 0


and the same code on 64 bit:

Quote:

FairTrackParP::FairTrackParP fq = (int)TMath::Sign(1.0, fQp); P =1.957 fQp = -0.5109 fq = -1
FairTrackParP::FairTrackParP fq= int (P * fQp); P =1.957 fQp = -0.5109 fq = -1


which explain why I could not reproduce this problem before!

Anyway, the change suggested by Stefano is now in SVN (-r 6568)


regards

Mohammad
 
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