Irène Joliot-Curie and Albert Einstein

Welcome to the web site of François-Xavier Gentit

I have studied at the E.T.H Zürich and I worked at the CEA Saclay. The picture above shows one oldtimer of each of these institutions. The picture below shows more oldtimers of the CEA.

I use this web site to provide people with these parts of my work which may be of general interest. During years, I have written specific Fortran software for specific experiments, and from all this, nothing remains. Ok, it has led to correct analysis of the experiments, and has allowed nice publications. But from all this work, many parts were of general interest, and I regret to-day not having made the effort of doing this general part in a form allowing others to use it, and also allowing me to keep and remember it. For that, it is necessary that an effort be made in documentation. Fortran and the non-existence of the web made this effort painful, and also the bad habit of making everything in a hurry.

But one day two miracles occured: the possibility to use C++, a much more readable language than Fortran, and ROOT. ROOT contains everything needed to make useful programs in C++, and to see how easy it is to document his code thanks to ROOT fascinated me. I also read the paper, quoted by the ROOT team:

  • The Cathedral and the Bazaar
  • by Eric Steven Raymond

    • an article that everybody should have read, which explains the surprisingly high benefit in the cleanliness of the code, if one exposes it to the use and scrutiny of others. At that time, I was asked to do a Monte-Carlo of optical photons for the CMS experiment, litrani. I decided to make it general purpose and not CMS specific, and to document it in such a way that it could be downloaded from the web and used by others, without any help from me. I had the delightful surprise of seeing that the article "The Cathedral and the bazaar" was entirely right: I had users all around the world, they gave me advices and reported about bugs they found, so that this piece of code is certainly the cleanest I ever wrote, in spite of its size. So please find here some general purpose applications or informations I wrote:

    General purpose software
    Application Size
    Description
    SLitrani 50M General purpose Monte-Carlo of optical photons, using the TGeo geometry of ROOT.
    Litrani 50M General purpose Monte-Carlo of optical photons. Old version of SLitrani, with a simple flat geometry.
    SplineFit 0.6M General solution for the handling of variable parameters
    0.5M Useful additions to "libPhysics" of ROOT concerning (real or complex) vectors, (real or complex) matrices, and multi-dimensional arrays.
    0.01M useful to show drawings or histograms into 2 pads
    10M Fit in case of hierarchal parameters
    Guide
    How to build programs based on ROOT, using Visual C++ 9.0 on Windows XP/vista/7, or ddd on Linux, or Eclipse on Linux
    muster ~0 example used in the previous "howto"
    Skeleton ~0 Creation of skeletons for a new class and other starting files