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Question 2 GDML Questions 

Forum: Geometry
Date: 12 Mar, 2015
From: Brent <Brent>


I rather recently began using Geant4.10.01, having previously used 4.9.6. There appear to be a couple of new "features" in the latest 3.1.1 version of GDML that is now incorporated that I don't completely understand. Unfortunately, I can't find release notes on GDML to see where these changes are called out, but was hoping someone might know more.

(1) I use the ENTITY capability of XML quite a bit, since most of my simulations uses the modular capabilities of GDML, In other words, when I have a mother volume including a child, I simply do

<file name="FILENAME">

This enables me to quickly set up a simulation with the mother including the child, or the child by itself, since the child is a completely syntactically correct gdml file. However, I've been using ENTITY to specify an overall "materials" file; that way I can use the same material over and over without having to rewrite it in every file. Since I include this file as an entity, however, it is read once for every single gdml file. So in reading the mother, it reads the file, then again when the child is read. This was never a problem before, but now it appears I get warning messages about repeated definitions of materials (a *lot* of them). While I don't care about warnings, I am a little concerned at how cross sections (using Hadron elastic physics, in particular) are being read. I'm worried, based on the amount of time it takes to set up a simulation, that every time my materials file is being read that these cross section files are being read, which is obviously for wasteful computationally.

Does anyone have any idea about this -- namely, is there any way to somehow tell Geant's GDML interpreter to just ignore xml/gdml files its already read (i.e., my materials file)?

(2) The other issue I appear to have is that I used to simply define all my materials AND elements with the <materials> tag. Now, it appears if I use that element in a molecular formula., i.e. with <composite n=X ref=X>, the interpreter can't find the element. I must explicitly define it as an element. On the other hand, it does still work in material mixtures, i.e. <fraction n=X ref=X>. What this has led me to is if I want to use, say, Carbon, in both a mixture and a molecule, I must make one with the <material> tag and one with the <element> tag (with different names of course).


Sorry for the long post and thanks for any help. These issues are not keeping me from running my simulations, I'd just like to understand them better and address them to save time.

Regards, Brent

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1 None: Re: 2 GDML Questions   (Witek Pokorski - 08 Apr, 2015)
2 Idea: Re: 2 GDML Questions   (Vladimir Ivanchenko - 08 Apr, 2015)
3 None: Re: 2 GDML Questions   (Brent - 15 Apr, 2015)
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