Added class description comments.
[u/mrichter/AliRoot.git] / HLT / misc / AliTransBit.cxx
CommitLineData
1a3c8f6e 1///////////////////////////////////////////////////////////////////////////////
2// //
3// Time Projection Chamber ADC bit compresion lookup table //
4// //
5//
6// Origin: Marian Ivanov , GSI Darmstadt //
7// //
8
9//
10/*
11 Conversion equation:
12 For AliTransBit_v1
13 dy/dx= Int_t(1+x/fX0)
14
15 For AliTransBit_v2
16 y =(2**bit0) ln(1+x/fX0) / ln(1+(2**bit1-1)/fX0)
17
18 where x0 is calculated in function GetOptimumX0()
19
20*/
21
22// Example Session //
23/*
24
25Int_t b0=10; // original number of bits
26 Int_t b1=8; // compressed
27
28 AliTransBit_v1 trans;
29 Int_t x0=TMath::Nint(TMath::Exp(b0*TMath::Log(2)));
30 Int_t x1=TMath::Nint(TMath::Exp(b1*TMath::Log(2)));
31 trans.SetBits(b0,b1);
32 trans.FindOptimumX0();
33 trans.Update();
34 cout<<trans.Get0to1(x0-2)<<"\n";
35 cout<<trans.Get1to0(x1-2)<<"\n";
36
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
40
41 for( Int_t i=0;i<x1-1;i++) cout<<i<<"\t"<<trans.Get1to0(i+1)-trans.Get1to0(i)<<"\n"; > tabled.txt
42
43
44
45*/
46//Begin_Html //
47/* //
48<img src="gif/AliTPCTransBit.gif">
49*/
50//End_Html
51// //
52// //
53///////////////////////////////////////////////////////////////////////////////
54
55
56#include "AliTransBit.h"
57#include "TMath.h"
58#include "iostream.h"
59
60ClassImp(AliTransBit)
61ClassImp(AliTransBit_v1)
62ClassImp(AliTransBit_v2)
63
64
65AliTransBit::AliTransBit()
66{
67 //
68 //
69 fTable0 = 0;
70 fTable1 = 0;
71 fBit0 = 10;
72 fBit1 = 8;
73 fX0 = 0;
74}
75
76AliTransBit::~AliTransBit()
77{
78 //
79 //default destructor
80 if (fTable0!=0) delete [] fTable0;
81 if (fTable1!=0) delete [] fTable1;
82}
83
84
85
86
87
88Double_t AliTransBit_v1::FindOptimumX0()
89{
90 //
91 //find x0 for which derivation at xder1 is equal 1
92 //
93 Int_t x0=TMath::Nint(TMath::Exp(fBit0*TMath::Log(2)));
94 Int_t x1=TMath::Nint(TMath::Exp(fBit1*TMath::Log(2)));
95
96 fX0 = ((x1-2)*(x1-2)/2.)/(x0-x1-1); //starting fX0
97 Int_t digit=0;
98 Int_t j;
99 Double_t weight=1;
100 for(j=0;(j<50)&&(digit!=(x0-1));j++){
101 Int_t olddigit=digit;
102 digit=0;
103 for (Int_t i=0; i<x1-1;i++) digit+= Int_t(1+Double_t(i)/fX0);
104 fX0*= (1.+weight*Double_t(digit)/Double_t(x0-1))/(1.+weight);
105 if ( ((olddigit-(x0-1)) * (digit-(x0-1))) <0 )
106 weight*=0.25;
107 // cout<<j<<"\t"<<fX0<<"\t"<<digit<<"\n";
108 }
109 // cout<<"End of iteration "<<j<<"\n";
110 //cout<<"digit..."<<digit<<"\n";
111 return fX0;
112}
113
114
115void AliTransBit_v1::Update()
116{
117 //
118 //construct lookup tables for loosy compresion from
119 if (fX0<1) fX0 = FindOptimumX0();
120 Int_t x0=TMath::Nint(TMath::Exp(fBit0*TMath::Log(2)));
121 Int_t x1=TMath::Nint(TMath::Exp(fBit1*TMath::Log(2)));
122
123 //fTable0 - conversion from bit0 coding to bit1 coding
124 if (fTable0!=0) delete fTable0;
125 fTable0= new Int_t[x0];
126 //fTable1 - conversion table from bit1 to bit0 coding
127 if (fTable1!=0) delete [] fTable1;
128 fTable1= new Int_t[x1];
129 //
130 Int_t digit=0;
131 for (Int_t i=0; i<x1-1;i++){
132 Int_t ddig=Int_t(1+Double_t(i)/fX0);
133 for (Int_t j=0;j<ddig;j++) if ((digit+j)<x0) fTable0[digit+j] = i;
134 fTable1[i]= digit+ddig/2;
135 digit+= ddig;
136 }
137 for (Int_t i=digit;i<x0-1;i++) fTable0[i]=x1-2;
138 fTable1[x1-1]=x0-1; //overflow
139 fTable0[x0-1]=x1-1; //overflow
140 return;
141}
142
143
144Double_t AliTransBit_v2::FindOptimumX0()
145{
146 //
147 //find x0 for which derivation at xder1 is equal 1
148 //
149 const Float_t xder1=1;
150 const Float_t dx=0.1;
151
152 Float_t x0=TMath::Exp(fBit0*TMath::Log(2));
153 Float_t x1=TMath::Exp(fBit1*TMath::Log(2));
154 Float_t deriv = 0;
155 Float_t x;
156 for (x=x1;( (x>1)&&(deriv<1)) ;x-=dx)
157 {
158 deriv = (x1-1)/( TMath::Log(1.+x0/x) *x *(1+xder1/x));
159 }
160 x+=dx/2.;
161 fX0 = x;
162 return fX0;
163}
164
165
166void AliTransBit_v2::Update()
167{
168 //
169 //construct lookup tables for loosy compresion from
170 if (fX0<1) fX0 = FindOptimumX0();
171 //Float_t x0=TMath::Nint(TMath::Exp(fBit0*TMath::Log(2)));
172 //Float_t x1=TMath::Nint(TMath::Exp(fBit1*TMath::Log(2)));
173 Int_t x0=TMath::Nint(TMath::Exp(fBit0*TMath::Log(2)));
174 Int_t x1=TMath::Nint(TMath::Exp(fBit1*TMath::Log(2)));
175
176 //fTable0 - conversion from bit0 coding to bit1 coding
177 if (fTable0!=0) delete fTable0;
178 fTable0= new Int_t[x0];
179
180 //fTable1 - conversion table from bit1 to bit0 coding
181 if (fTable1!=0) delete [] fTable1;
182 fTable1= new Int_t[x1];
183
184 //
185 Int_t i;
186
187 for ( i=0; i<x0;i++)
188 fTable0[i] =TMath::Nint((x1-0.501)*TMath::Log(1.+Float_t(i)/fX0)/
189 TMath::Log(1.+(x0-1)/fX0));
190
191 Int_t old0=-1;
192 Int_t old1=-1;
193 Int_t new1;
194 for ( i=0; i<x0;i++){
195 new1 = fTable0[i];
196 if (new1!=old1){
197 if (old1>=0) fTable1[old1] =(old0+i)/2;
198 old0 = i;
199 old1 = new1;
200 }
201 }
202 fTable1[old1]=TMath::Nint((Float_t)(old0+x0)/2);
203
204 return;
205}