Hi,Everyone,
I just need to caculate some function values. Also it should not be hard
to draw the funcation. But the Root always complain divided by zero.
If i do not call the function in the loop, it is fine and get what i
expect value. Since my code is rathen simple. i paste it here. I use
Root 3.03 on osf1 system.
#include "TH1.h"
#include "TF1.h"
#include "TROOT.h"
#include "TStyle.h"
Double_t f(Double_t z)
{
Double_t returnValue = (1+0.5*z)*(1+0.5*z)*TMath::log(1/z)-
0.5*(1-z)*(3+z);
return returnValue;
}
Double_t fluxMR(Double_t beam,Double_t m)
{
Double_t s = 4*beam*beam;
Double_t me = 0.511/1000.0;
Double_t alpha = 1/137.036;
Double_t returnValue;
Double_t z = m*m/s;
Double_t t1 = TMath::log(s/(me*me))-1;
Double_t t2 = TMath::log(s/(m*m));
returnValue = 3*8*alpha*alpha/(m*m*m)*
( f(z)*t1*t1-1/3.0*t2*t2*t2 );
}
Double_t flux(Double_t *beam, Double_t *par)
{
Double_t etacM = par[0];
Double_t etacPrimeM = par[1];
Double_t returnValue = fluxMR(beam[0],etacPrimeM)/fluxMR(beam[0],etacM);
return returnValue;
}
void calcflux()
{
Double_t par[2];
Double_t beam[1];
beam[0] = 5.28;
par[0] = 2.98;
par[1] = 3.64;
Double_t res;
for(Int_t i = 0 ; i < 100 ; ++i){ //if do not loop, it is fine.
beam[0] = 4.7;
// beam[0] = 4.7+(5.5-4.7)/100.0*i;
cout<<flux(beam,par)<<endl;
}
}
Thanks
Gong Datao
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