Re: [ROOT] TQObject::Emit()

From: Valeriy Onuchin (onuchin@fnal.gov)
Date: Mon Mar 26 2001 - 04:44:29 MEST


 Hi Anton,
check a simple stress test of signals/slots below.
 - the result on Pentium III 800 Mhz is 15 microseconds per call with Emit.
 - the result for calls without Emit is 0.015 microseconds per call.
 - the results for compiled executable program are the same.

Regards.    Valeriy


root [0] .x stress.C++
Creating shared library /home/onuchin/tmp/./stress_C.so
Class A: Streamer() not declared
Class A: ShowMembers() not declared
Nevents 1000000, Real time 0:0:14, CP time 14.900


To compile stanalone executable program:


    $root -b -q >/dev/null stress.C | echo '{gSystem->CompileMacro("stress.C","kf");}' >tmp.C
    $g++ -o stress stress.C `root-config --cflags --libs` -DSTANDALONE





---------------------------- stress.C ---------------------------------

#include <TQObject.h>
#include <RQ_OBJECT.h>
#include <TStopwatch.h>

///////////////////////////////////////////////////////////////////////
class A
{
RQ_OBJECT()

private:
   Int_t fValue;
public:
   A():fValue(0) { }
   ~A() { }

   void  SetValue(Int_t value);  //*SIGNAL*
};


//___________________________________________________________________
void A::SetValue(Int_t value)
{
   // Set new value.
   // Emit signal "SetValue(Int_t)" with a single parameter

   if(value!=fValue) {
      fValue=value;
      Emit("SetValue(Int_t)",fValue);
   }
}

/////////////////////////////////////////////////////////////////////
//___________________________________________________________________
void stress()
{
   // Simple tests on signals, slots and connections

   A a;
   A b;

   a.Connect("SetValue(Int_t)","A",&b,"SetValue(Int_t)");

   const Int_t nevents = 1000000;

   TStopwatch timer;
   timer.Start();
   for(int i=0; i<nevents; i++) a.SetValue(i);
   timer.Stop();
   printf("Nevents %d, ",nevents);
   timer.Print();
}

///////////////////////////// Main program ////////////////////////
#ifdef STANDALONE

#include <TROOT.h>
#include <TApplication.h>
#include <TSystem.h>

//---- Main program -------------------------------------------------

TROOT root("tst","Stress test of signal/slots");

int main(int argc, char **argv)
{
   gSystem->Load("./tst_C");
   TApplication* app = new TApplication("",0,0);
   stress();
   return 0;
}
#endif //STANDALONE

---------------------------- stress.C ---------------------------------



Anton Fokin wrote:

> Hi Valery,
>
> I meant that Emit("DataChanged()") call might be time consuming since you
> take an argument as char string, compress it and loop over class and object
> signal/connection lists (why don't you use hash table, btw?). I was curious
> how it is done in Qt/moc. If you say it does nearly the same, no probs. A
> benchmark test could be like
>
> while (end_test) {
>   DataChanged();
> }
>
> with and without Emit() in DataChanged(). Of course nobody should be
> connected to this signal. On the other hand result will depend on how long
> are lists of signals...
>
> > > I am also not sure what it takes in Qt/moc. In Qt you do not need to
> call
> > > Emit() in a signal method - the signal will be emitted automatically
> once
> > > the method is declared as signal.
> > >
> >
> > ("It is not correct ..."  Valery Fine;)
> >
> >
> > I studied Qt code ... it also uses "Emit" method inside "signal"
> > Suppose looking at the code produced after MOC preprocessor will reveal
> it.
> > > I am also not sure what it takes in Qt/moc. In Qt you do not need to
> call
> > > Emit() in a signal method - the signal will be emitted automatically
> once
> > > the method is declared as signal.
> > >
> >
> > ("It is not correct ..."  Valery Fine;)
> >
> >
> > I studied Qt code ... it also uses "Emit" method inside "signal"
> > Suppose looking at the code produced after MOC preprocessor will reveal
> it.
>
> Yes, that was the questions. I meant that a user does not need to put Emit()
> in the body of a signal method in Qt - moc does it. I asked if it is done in
> a clever way since moc has control over the code and can make some "direct"
> substitutions.
>
> Regards,
> Anton
>
> http://www.smartquant.com
>
> ----- Original Message -----
> From: Valeriy Onuchin <onuchin@fnal.gov>
> To: Anton Fokin <anton.fokin@smartquant.com>
> Cc: <roottalk@pcroot.cern.ch>
> Sent: Thursday, March 22, 2001 11:27 PM
> Subject: Re: [ROOT] TQObject::Emit()
>
> > Hi Anton,
> >
> > Anton Fokin wrote:
> >
> > >
> > >
> > > Hi,
> > >
> > > If I want to use singal/slots I have to add Emit("DataChanged()"); or
> alike
> > > in my TQObject inherited class method to emit a signal. I am curious if
> this
> > > call is costly or not.
> >
> >  What cost do you mean?
> >
> >  Memory?
> >
> >     TQObject has 2 data members which are pointers to
> Lists( sizeof(TList*) = 4 ).
> >     These TLists are created(new TList) only when connection is
> established
> >     ( sizeof(TList) = 44 ). During creation of connection some internal
> structures
> >     are also initiated, but it was designed to make it minimal amd reuses
> existent ones.
> >
> >
> > >
> > >
> > > I am also not sure what it takes in Qt/moc. In Qt you do not need to
> call
> > > Emit() in a signal method - the signal will be emitted automatically
> once
> > > the method is declared as signal.
> > >
> >
> > ("It is not correct ..."  Valery Fine;)
> >
> >
> > I studied Qt code ... it also uses "Emit" method inside "signal"
> > Suppose looking at the code produced after MOC preprocessor will reveal
> it.
> >
> >
> >
> > >
> > > So could you comment on performance of Emit("DataCahnged()") decoding
> (with
> > > CINT dict, etc.) compare to Qt moc processing.
> >
> > Fair comparison of benchmark tests is always difficult task
> > ( btw it's not a bad business
> http://www.tpc.org/information/about/join.asp )
> >
> > Suggest the "fair test" and I/we can try it.
> >
> >
> > Regards.    Valeriy
> >
> >
> >



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