[Castor-users] Loss of TOF precision after converting ROOT to TXT

[tmerlin]

Hi Zipai,

I didn't look into details, but it appears to be a float/double issue, 
or a precision problem when you write your txt file.

Maybe you could set the precision of the value in the output txt file in 
your c++ script with /std::setprecision(x)/.

Hope this helps,
Thibaut

  On 26/04/2021 17:56, Zipai Wang wrote:
> Dear CASToR developers and users
>
> I am post-processing the root list-mode data generated from the GATE 
> simulation and reconstructing it using the CASToR. First I convert the 
> ROOT to TXT, after the post-processing, I convert the TXT back to ROOT 
> for the reconstruction. Most of the things went well, and the image 
> can be successfully reconstructed by CASToR.
>
> However, recently I am trying to add TOF in the recon, but soon 
> realize that the txt file converted from ROOT has a lower TOF data 
> precision. I have output the .dat file from GATE directly for a 
> comparison: For example, In the txt file converted from ROOT, I got 
> TOF = 4.83994e-06 for eventID 30. In .dat, I got  TOF = 
> 4.83994034373751110439431e-06 for the same event.
>
> The loss of precision basically ruined the image since every event got 
> the same time difference. Although I can bypass the loss of precision 
> during the root to txt by using the .dat files, I am worrying that the 
> same thing will happen again when I convert txt back to ROOT.
>
> Apologize that I am very new to c programming and ROOT. I attached the 
> converting code I am currently using. May someone point out where is 
> the problem, please. Thank you very much for your attention, 
> appreciate it!
>
>
>
> Cheers!
> -- 
> Zipai Wang
> Biomedical Engineering PhD student
> Stony Brook University
>
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-- 
Thibaut MERLIN -- PhD

Docteur en Imagerie Médicale au Laboratoire de Traitement de l'Information Medicale (LaTIM - INSERM UMR 1101)
Institut Brestois de recherche en Bio-Santé (IBRBS)
12 Avenue Foch, 29200 Brest, FRANCE
Tel: 06.75.12.24.90

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