1 ///////////////////////////////////////////////////////////////////////////////
3 // Time Projection Chamber ADC bit compresion lookup table //
6 // Origin: Marian Ivanov , GSI Darmstadt //
16 y =(2**bit0) ln(1+x/fX0) / ln(1+(2**bit1-1)/fX0)
18 where x0 is calculated in function GetOptimumX0()
25 Int_t b0=10; // original number of bits
26 Int_t b1=8; // compressed
29 Int_t x0=TMath::Nint(TMath::Exp(b0*TMath::Log(2)));
30 Int_t x1=TMath::Nint(TMath::Exp(b1*TMath::Log(2)));
32 trans.FindOptimumX0();
34 cout<<trans.Get0to1(x0-2)<<"\n";
35 cout<<trans.Get1to0(x1-2)<<"\n";
37 // to produce table of
38 for( Int_t i=0;i<x1;i++) cout<<i<<"\t"<<trans.Get1to0(i)<<"\n"; > table1to0.txt
39 for( Int_t i=0;i<x0;i++) cout<<i<<"\t"<<trans.Get0to1(i)<<"\n"; > table0to1.txt
41 for( Int_t i=0;i<x1-1;i++) cout<<i<<"\t"<<trans.Get1to0(i+1)-trans.Get1to0(i)<<"\n"; > tabled.txt
48 <img src="gif/AliTPCTransBit.gif">
53 ///////////////////////////////////////////////////////////////////////////////
56 #include "AliTransBit.h"
62 ClassImp(AliTransBit_v1)
63 ClassImp(AliTransBit_v2)
66 AliTransBit::AliTransBit()
77 AliTransBit::~AliTransBit()
81 if (fTable0!=0) delete [] fTable0;
82 if (fTable1!=0) delete [] fTable1;
89 Double_t AliTransBit_v1::FindOptimumX0()
92 //find x0 for which derivation at xder1 is equal 1
94 Int_t x0=(Int_t)rint(exp(fBit0*log(2)));
95 Int_t x1=(Int_t)rint(exp(fBit1*log(2)));
97 fX0 = ((x1-2)*(x1-2)/2.)/(x0-x1-1); //starting fX0
101 for(j=0;(j<50)&&(digit!=(x0-1));j++){
102 Int_t olddigit=digit;
104 for (Int_t i=0; i<x1-1;i++) digit+= Int_t(1+Double_t(i)/fX0);
105 fX0*= (1.+weight*Double_t(digit)/Double_t(x0-1))/(1.+weight);
106 if ( ((olddigit-(x0-1)) * (digit-(x0-1))) <0 )
108 // cout<<j<<"\t"<<fX0<<"\t"<<digit<<"\n";
110 // cout<<"End of iteration "<<j<<"\n";
111 //cout<<"digit..."<<digit<<"\n";
116 void AliTransBit_v1::Update()
119 //construct lookup tables for loosy compresion from
120 if (fX0<1) fX0 = FindOptimumX0();
121 Int_t x0=(Int_t)rint(exp(fBit0*log(2)));
122 Int_t x1=(Int_t)rint(exp(fBit1*log(2)));
124 //fTable0 - conversion from bit0 coding to bit1 coding
125 if (fTable0!=0) delete fTable0;
126 fTable0= new Int_t[x0];
127 //fTable1 - conversion table from bit1 to bit0 coding
128 if (fTable1!=0) delete [] fTable1;
129 fTable1= new Int_t[x1];
132 for (Int_t i=0; i<x1-1;i++){
133 Int_t ddig=Int_t(1+Double_t(i)/fX0);
134 for (Int_t j=0;j<ddig;j++) if ((digit+j)<x0) fTable0[digit+j] = i;
135 fTable1[i]= digit+ddig/2;
138 for (Int_t i=digit;i<x0-1;i++) fTable0[i]=x1-2;
139 fTable1[x1-1]=x0-1; //overflow
140 fTable0[x0-1]=x1-1; //overflow
145 Double_t AliTransBit_v2::FindOptimumX0()
148 //find x0 for which derivation at xder1 is equal 1
150 const Float_t xder1=1;
151 const Float_t dx=0.1;
153 Float_t x0=exp(fBit0*log(2));
154 Float_t x1=exp(fBit1*log(2));
157 for (x=x1;( (x>1)&&(deriv<1)) ;x-=dx)
159 deriv = (x1-1)/( log(1.+x0/x) *x *(1+xder1/x));
167 void AliTransBit_v2::Update()
170 //construct lookup tables for loosy compresion from
171 if (fX0<1) fX0 = FindOptimumX0();
172 //Float_t x0=(Int_t)rint(exp(fBit0*log(2)));
173 //Float_t x1=(Int_t)rint(exp(fBit1*log(2)));
174 Int_t x0=(Int_t)rint(exp(fBit0*log(2)));
175 Int_t x1=(Int_t)rint(exp(fBit1*log(2)));
177 //fTable0 - conversion from bit0 coding to bit1 coding
178 if (fTable0!=0) delete fTable0;
179 fTable0= new Int_t[x0];
181 //fTable1 - conversion table from bit1 to bit0 coding
182 if (fTable1!=0) delete [] fTable1;
183 fTable1= new Int_t[x1];
189 fTable0[i] =(Int_t)rint((x1-0.501)*log(1.+Float_t(i)/fX0)/
195 for ( i=0; i<x0;i++){
198 if (old1>=0) fTable1[old1] =(old0+i)/2;
203 fTable1[old1]=(Int_t)rint((Float_t)(old0+x0)/2);