Life as a Physicist

Not so much interest to most people here…

So, on Windows, there has been the occasion that I’ve needed to build ROOT. In particular, on windows, this is because the released version of ROOT is not built against python. I also find myself doing lots of building building when buts are found in root (yeah, I know, ROOT doesn’t have bugs).

The standard way to do the build is download and install cygwin. It is a rather heavy install, however, as any of you who have installed it know. Axel, a member of the ROOT team, put together a minimal set of tools that will build ROOT using the MSVC compilers. I built a small UI on top of that along with an installer to make it easier to get onto your machine.

I found this pretty useful for getting my work done, so I thought I’d release it. Actually, it has been finished for months, I just never seemed to get around to finishing off the last bit. So, here it is. The UI is horrible, but it works…

I complain about ROOT a lot. However, one thing I have to say is that when you report a bug it is only a matter of days before it gets fixed in their source code repository. Philippe Canal just did a whole bunch of work after I found a few bugs in the MakeProxy code that means it will now be possible to use weird variables like vector<vector<double> > without having to think (these are produced by the EventView tool in ATLAS). Nice!

BTW, MakeProxy is a step back in time. Remember PAW (ok, I know, some of you are still using it). One of the nice things about the FORTRAN macros back then was the auto-loading of ntuple columns. Only what you referenced in your FORTRAN code was loaded. That isn’t the case in ROOT — it has no good way to scan compiled C++ code to determine what is used. Philippe wrote an automatic proxy-generator that replaces each ntuple branch with a bit of code that first makes sure the data is read in before accessing it (I’m pretty sure Philippe was the progenitor of the idea). In the end this has the effect of doing the same thing — only what is needed is read. I’ve seen x10 speed-ups caused by this. The only it can’t do is look inside a custom compiled object — so this doesn’t buy you as much if you are running in that case.

Otherwise, I definitely recommend checking out TTree::MakeProxy.