LHCb Core Software Meeting

Date and Location

10:30 - 12:15
CERN (2-R-030)


Alex Grecu, Ben, Gloria Corti, Hubert Degaudenzi, Joel Closier, Marco Cattaneo, Marco Clemencic (minutes), Markus Frank, Rob Lambert, Thomas Hartmann (EVO)



Marco Ca.: we will be asked in the near future if we want to keep or drop Windows.

Discussion about Windows support

A long discussion followed, which I try to summarize here (including some more information than the one exchanged during the meeting).

The main reasons to build our software on Windows were (not in order of relevance):

  • non-GNU compiler (different/more warnings)
  • better development/debug environment
  • possibility of running offline on laptops
  • different operating system (limit the possibility of using non-portable libraries)

The first three points are already addressed without the need of Windows

  • non-GNU compiler: we are using the Intel compiler (even if there are some licensing issues that should be addressed) and Coverity, in the future we may have support for clang/LLVM
  • development/debug environment: nowadays we almost do not use Visual Studio and Eclipse reduces even more its need
  • running on laptops: we can use CERNVM

The last point is still valid. There is a good value in keeping our software portable and we must do it even if dropping Windows. The main problem is that if we do not force the developers to write code that works on Windows, it will be much more difficult (almost impossible) to keep our code portable.

Despite the fact that portable code is better and our code is portable, the adoption of a new platform is heavily limited by the way we build and configure it (we need LCGCMT binaries and configuration). Moreover, some developers do not see the need of the portability to Windows, or they simply do not care.

We should also take into account the cost (in terms of men power) of the support for Windows.

Building the full LHCb stack on Windows is not a problem (the release is usually smooth, except for few cases).

What really costs is the maintenance of the infrastructure, mainly of the nightly builds, which are the basic tool to test the portability of new code. Most of the problems in the Windows nightly builds are due to limitations of the system and not to the code itself.

Another big cost is the maintenance of the Windows builds of the LCG externals (the AA projects are not really a problem). SFT groups is kindly keeping the Windows builds in sync, wherever possible, with the Linux ones, but it's men-power spent only for LHCb, so it's difficult to justify it for a group that is supposed to work on tasks meant to support more than one experiment.

Note: Gaudi is not considered in this discussion, because it will support Windows (e. g. for other customers than LHCb). The point of the discussion is if LHCb should still ask SFT/AA to build everything on Windows for us.


Please, add here comments and contributions to the discussion.

-- Main.MarcoClemencic - 15-Sep-2011

Round Table


  • item 1
  • item 2

-- MarcoClemencic - 15-Sep-2011

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Topic revision: r2 - 2011-09-15 - MarcoClemencic
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