Re: performance of a program with MakeClass vs MakeSelector, and global variable

Hello Marc,

I would make that histogram a member of your class, then later when the Loop() is finished you return a pointer of that histogram using a public member of your class. Another solution is to make that histogram a global var. That would be the very easy solution. Either way you will be able to compile your code.

Another good reason to compile your code. If you are using a lot of stdlib stuff ... compiling is highly recommended.

cheers !

John

On Tue, 2010-07-06 at 22:28 +0200, Marc Escalier wrote:
> thanks John for your suggestions,
>
> my problem is that it doesn't compile for the following reason :
> when compiling, the histogram is unknown to the method of the class :
>
> the reason is that :
>
> {
> TH1F *myhisto
>
> InstanceOfClass.Loop(*without parameters*)
> }
>
> with :
> InstanceOfClass.Loop()
> {
> work on myhisto that still is accessible "because of the rules of cint"
> }
>
> so it would not compile (i do interpreted code because it is easier to
> debug and because the gain in speed when compiling is only 10 %. I
> showed to Rene some time ago that indeed the gain was only 10 % for the
> specific way of class that i'm using where there is plenty of vectors,
> which is not optimized for root. But i don't have the choice about the
> class : it is an "official" format.)
>
> thanks
> ======================
> On Tue, 6 Jul 2010, John Idarraga wrote:
>
> > By the way, before running valgrind --tool=callgrind, compile your macro
> > with debugging symbols
> >
> > 1) if compiling using ACLIC
> >
> > .L mystuff.C++g
> >
> > 2) if you are compiling by hand you need to pass this flag to g++
> >
> > -g3
> >
> > cheers,
> >
> > John
> >
> > On Tue, 2010-07-06 at 19:14 +0200, Marc Escalier wrote:
> >> Hello,
> >>
> >> i observed a strange phenomena with root (i guess it doesn't depend on
> >> the version, but just in case, it is root 5.22.)
> >>
> >> Let's consider a minimum program developped from a MakeClass() and a
> >> concurrent one with MakeSelector()
> >> *if the two programs don't fill histogram, i find the same performance
> >> in time of execution
> >>
> >> *if i fill the histogram with a MakeClass approach or a MakeSelector
> >> approach, for which the histogram has been declared in the main program
> >> as a global variable
> >> then the MakeSelector approach is about 10 times slower than the
> >> MakeClass approach (doing exactly same stuff) (and with desactivation on
> >> almost all the branches to speed up the process in the two cases)
> >>
> >> the program is something like :
> >>
> >> {
> >> Declaration of a histogram
> >> Call Instance of a Class and loop on it and fill the histogram with
> >> dummy values
> >> or
> >> Call Instance of a Selector and loop on it and fill the histogram with
> >> dummy values
> >> }
> >>
> >> *if now, i put the histogram in "local variables" in the class of the
> >> Selector (declaration in the header .h and memory allocation in the Begin())
> >> then the performance of the MakeSelector approach is twice faster as
> >> compared to the MakeClass approach
> >>
> >> Would you have an idea of the behaviour
> >>
> >> thank you very much
> >>
> >> just in case you would need more info on the program, it is here (lxplus) :
> >> /afs/cern.ch/user/e/escalier/public/ForRene
> >> time root -b -q -x main.C
> >> to see the differences to apply, you can replace the differences by
> >> making comment/uncomment of the parts with "option 1", "option 2",
> >> "option 3"
> >> (
> >> "grep option 1" *
> >> "grep option 2" *
> >> "grep option 3" *
> >> )
> >>
> >
> >
>
Received on Tue Jul 06 2010 - 22:36:27 CEST