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Re: MC data productions [message #5304 is a reply to message #5134]

Wed, 24 October 2007 12:00

Florian Uhlig
Messages: 424
Registered: May 2007

first-grade participant

From: *gsi.de

I looked into the problem with the cherenkov photons on 64bit machines.
As reported in the Software Meeting on 18.10.07 with the newest version of TGeant3 the problem disappeared and the control spectra look normal (see test.mc.RichTestSim.newgeant3.ps)

Checking the changes in the Geant3 code between the two versions there was only no change in the code which could explain the difference between the two Geant3 versions, but there was also a
change in the Makefile for x86_64. In the new Makefile there is a new compiler option "-fno-f2c".

Compiling the old Geant3 code with this additional option also for the old code the Rich control spectra look normal (see test.mc.RichTestSim.oldgeant3.newflag.ps)

According to the information of the g77 manpage normally all code generated by g77 is compatible with code generated with f2c. using "-fno-f2c" the generated code is not compatible with code generated by f2c but uses the GNU calling conventions instead.
This mainly effects the return values

>>The f2c calling conventions require functions that return
>>type "REAL(KIND=1)" to actually return the C type "double",
>>and functions that return type "COMPLEX" to return the
>>values via an extra argument in the calling sequence that
>>points to where to store the return value.

>>Under the GNU calling conventions, such functions simply
>>return their results as they would in GNU C---"REAL(KIND=1)"
>>functions return the C type "float", and "COMPLEX" functions
>>return the GNU C type "complex" (or its "struct" equivalent).

>>Caution: If -fno-f2c is used when compiling any source file
>>used in a program, it must be used when compiling all
>>Fortran source files used in that program.

Since TGeant3 is mostly an interface from C++ to the old fortran routines this differences can explain the observed effect. Why this effect is only seen with cherenkov photons i don't know.

As a summary i would say the problem is solved and partly understood.

On /misc/cbmsoft/Debian64/new i will use the old Geant3 version with the new compiler flag, to have consistent versions of the different libraries on 32 and 64bit.

Attachment: test.mc.RichTestSim.oldgeant3.newflag.ps
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Attachment: test.mc.RichTestSim.newgeant3.ps
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[Message index]

		CBMROOT Release AUG07 By: Volker Friese on Wed, 12 September 2007 19:05
		Correction: Still "old" TOF hit producer in the release By: Volker Friese on Mon, 17 September 2007 16:24
		MC data production report By: Volker Friese on Wed, 19 September 2007 12:32
		MC data productions By: Volker Friese on Sun, 23 September 2007 22:36
		Re: MC data productions By: Claudia Höhne on Mon, 01 October 2007 17:13
		Re: MC data productions By: Florian Uhlig on Wed, 24 October 2007 12:00
		Re: MC data productions By: Radoslaw Karabowicz on Wed, 03 October 2007 12:31
		MC data production AUG07 By: Volker Friese on Thu, 18 October 2007 15:29
		Bug fix By: Volker Friese on Fri, 02 November 2007 15:58

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