Comment changes for htlm docu.
[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"
b328544b 57
58#include <iostream.h>
59#include <math.h>
1a3c8f6e 60
61ClassImp(AliTransBit)
62ClassImp(AliTransBit_v1)
63ClassImp(AliTransBit_v2)
64
65
66AliTransBit::AliTransBit()
67{
68 //
69 //
70 fTable0 = 0;
71 fTable1 = 0;
72 fBit0 = 10;
73 fBit1 = 8;
74 fX0 = 0;
75}
76
77AliTransBit::~AliTransBit()
78{
79 //
80 //default destructor
81 if (fTable0!=0) delete [] fTable0;
82 if (fTable1!=0) delete [] fTable1;
83}
84
85
86
87
88
89Double_t AliTransBit_v1::FindOptimumX0()
90{
91 //
92 //find x0 for which derivation at xder1 is equal 1
93 //
b328544b 94 Int_t x0=(Int_t)rint(exp(fBit0*log(2)));
95 Int_t x1=(Int_t)rint(exp(fBit1*log(2)));
1a3c8f6e 96
97 fX0 = ((x1-2)*(x1-2)/2.)/(x0-x1-1); //starting fX0
98 Int_t digit=0;
99 Int_t j;
100 Double_t weight=1;
101 for(j=0;(j<50)&&(digit!=(x0-1));j++){
102 Int_t olddigit=digit;
103 digit=0;
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 )
107 weight*=0.25;
108 // cout<<j<<"\t"<<fX0<<"\t"<<digit<<"\n";
109 }
110 // cout<<"End of iteration "<<j<<"\n";
111 //cout<<"digit..."<<digit<<"\n";
112 return fX0;
113}
114
115
116void AliTransBit_v1::Update()
117{
118 //
119 //construct lookup tables for loosy compresion from
120 if (fX0<1) fX0 = FindOptimumX0();
b328544b 121 Int_t x0=(Int_t)rint(exp(fBit0*log(2)));
122 Int_t x1=(Int_t)rint(exp(fBit1*log(2)));
1a3c8f6e 123
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];
130 //
131 Int_t digit=0;
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;
136 digit+= ddig;
137 }
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
141 return;
142}
143
144
145Double_t AliTransBit_v2::FindOptimumX0()
146{
147 //
148 //find x0 for which derivation at xder1 is equal 1
149 //
150 const Float_t xder1=1;
151 const Float_t dx=0.1;
152
b328544b 153 Float_t x0=exp(fBit0*log(2));
154 Float_t x1=exp(fBit1*log(2));
1a3c8f6e 155 Float_t deriv = 0;
156 Float_t x;
157 for (x=x1;( (x>1)&&(deriv<1)) ;x-=dx)
158 {
b328544b 159 deriv = (x1-1)/( log(1.+x0/x) *x *(1+xder1/x));
1a3c8f6e 160 }
161 x+=dx/2.;
162 fX0 = x;
163 return fX0;
164}
165
166
167void AliTransBit_v2::Update()
168{
169 //
170 //construct lookup tables for loosy compresion from
171 if (fX0<1) fX0 = FindOptimumX0();
b328544b 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)));
1a3c8f6e 176
177 //fTable0 - conversion from bit0 coding to bit1 coding
178 if (fTable0!=0) delete fTable0;
179 fTable0= new Int_t[x0];
180
181 //fTable1 - conversion table from bit1 to bit0 coding
182 if (fTable1!=0) delete [] fTable1;
183 fTable1= new Int_t[x1];
184
185 //
186 Int_t i;
187
188 for ( i=0; i<x0;i++)
b328544b 189 fTable0[i] =(Int_t)rint((x1-0.501)*log(1.+Float_t(i)/fX0)/
190 log(1.+(x0-1)/fX0));
1a3c8f6e 191
192 Int_t old0=-1;
193 Int_t old1=-1;
194 Int_t new1;
195 for ( i=0; i<x0;i++){
196 new1 = fTable0[i];
197 if (new1!=old1){
198 if (old1>=0) fTable1[old1] =(old0+i)/2;
199 old0 = i;
200 old1 = new1;
201 }
202 }
b328544b 203 fTable1[old1]=(Int_t)rint((Float_t)(old0+x0)/2);
1a3c8f6e 204
205 return;
206}