[Halld-offline] reducing file sizes

[David Lawrence]

Hi All,

    The DMCThrown information is contained in the reaction tags. The 
mctrajectory section is only for recording details about every step of 
the particles tracked by GEANT during simulation. This is very useful 
for debugging of charged particle tracking but it is very unlikely you 
will need this for calorimetry work. You should go ahead and drop the 
mctrajectory section, but it probably won't change the file size unless 
you went to the trouble of turning on storage of trajectory points.

Regards,
-David

Matthew Shepherd wrote:
> I'm not so sure about this... if MCThrown is used in the *parametric*  
> simulation of tracks then it needs to be there.  The calorimeter  
> reconstruction attempts to flag hits produced by the interaction of  
> charged particles with the calorimeter.
>
> -Matt
>
>
> On Oct 7, 2009, at 5:07 PM, Richard Jones wrote:
>
>   
>> Blake,
>>
>> All of the MC information about the event that was simulated is  
>> stored in the <reaction> tag.  The <mctrajectory> tag only contains  
>> cheat information about actual tracks going through the detector.  I  
>> didn't write the DMCThrown class, but The term "MCThrown" would  
>> suggest that it is only concerned with the original vertex, not with  
>> what paths the particles took subsequently as they traversed the  
>> detectors.  So I would say that you can wipe out the <mctrajectory>  
>> tag and see no effect in the calorimeter reconstruction.
>>
>> -Richard J.
>>
>>
>>
>> Blake Leverington wrote:
>>     
>>> ok, I think maybe I wasn't clear or there's something I don't  
>>> understand. Since I'm doing background MC work I need to know what  
>>> particle types and reactions pass my reconstruction cuts so I still  
>>> probably need  <mctrajectory> tag. I assume this is where the  
>>> DMCThrown information comes from.  But I was also under the  
>>> impression that <reaction> contains information about the vertex  
>>> and so on for reconstructing angles.
>>>
>>> -Blake
>>>
>>> Richard Jones wrote:
>>>
>>>       
>>>> Blake,
>>>>
>>>> The rules are simple: just cut out entire tags (anything goes) to  
>>>> kill what you don't want.  I think this is too clear to risk  
>>>> mistakes.  Simply if you kill a tag then all of its contents  
>>>> disappear with it.  It sounds to me like you still want to kill  
>>>> the <reaction> ... </reaction> tag and the  
>>>> <mctrajectory>..</.mctrajectory> tag.  After that, you are down to  
>>>> basically just what you want.
>>>>
>>>> -Richard J.
>>>>
>>>> Blake Leverington wrote:
>>>>
>>>>         
>>>>> Hi Richard,
>>>>>
>>>>> Ok, I followed your instructions and everything went smoothly, so  
>>>>> thank you. I ended up with a 70% reduction in my files sizes,  
>>>>> 165MB down to 51MB. I've attached my edited hddm header file,  
>>>>> could you take a quick look to see if there is anything else I  
>>>>> could cut out? I think I took out everything unwanted, I think,   
>>>>> but I'm not familiar enough with the hddm formatting.  All I  
>>>>> require is photon reconstruction in the FCAL and BCAL and the  
>>>>> truth information.
>>>>>
>>>>> Cheers,
>>>>> -Blake
>>>>>
>>>>>
>>>>>           
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>
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-- 

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 David Lawrence Ph.D.
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