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1 // 1 //
2 // ******************************************* 2 // ********************************************************************
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4 // * 4 // * *
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24 // ******************************************* 21 // ********************************************************************
25 // 22 //
26 // G4ImplicitEuler implementation << 23 //
>> 24 // $Id: G4ImplicitEuler.cc,v 1.6 2003/06/16 16:51:13 gunter Exp $
>> 25 // GEANT4 tag $Name: geant4-05-02-patch-01 $
>> 26 //
27 // 27 //
28 // Implicit Euler: 28 // Implicit Euler:
29 // 29 //
30 // x_1 = x_0 + h/2 * ( dx(t_0,x_0) + dx 30 // x_1 = x_0 + h/2 * ( dx(t_0,x_0) + dx(t_0+h,x_0+h*dx(t_0,x_0) ) )
31 // 31 //
32 // Second order solver. << 32 // second order solver
33 // Take the current derivative and add it to t 33 // Take the current derivative and add it to the current position.
34 // Take the output and its derivative. Add the 34 // Take the output and its derivative. Add the mean of both derivatives
35 // to form the final output. << 35 // to form the final output
>> 36 //
>> 37 // W.Wander <wwc@mit.edu> 12/09/97
>> 38 // 6.11.98 V.Grichine, new constructor, fNumberOfVariables
36 // 39 //
37 // Author: W. Wander <wwc@mit.edu>, 12.09.1997 <<
38 // ------------------------------------------- <<
39 40
40 #include "G4ImplicitEuler.hh" 41 #include "G4ImplicitEuler.hh"
41 #include "G4ThreeVector.hh" 42 #include "G4ThreeVector.hh"
42 43
43 ////////////////////////////////////////////// 44 /////////////////////////////////////////////////////////////////////////
44 // 45 //
45 // Constructor 46 // Constructor
46 47
47 G4ImplicitEuler::G4ImplicitEuler(G4EquationOfM << 48 G4ImplicitEuler::G4ImplicitEuler(G4Mag_EqRhs *EqRhs,
48 G4int numberO << 49 G4int numberOfVariables):
49 : G4MagErrorStepper(EqRhs, numberOfVariables << 50 G4MagErrorStepper(EqRhs, numberOfVariables)
50 { 51 {
51 unsigned int noVariables = std::max(numberOf << 52 unsigned int noVariables= std::max(numberOfVariables,8); // For Time .. 7+1
52 dydxTemp = new G4double[noVariables] ; 53 dydxTemp = new G4double[noVariables] ;
53 yTemp = new G4double[noVariables] ; 54 yTemp = new G4double[noVariables] ;
54 } 55 }
55 56
56 57
57 ////////////////////////////////////////////// 58 ////////////////////////////////////////////////////////////////////////
58 // 59 //
59 // Destructor 60 // Destructor
60 // << 61
61 G4ImplicitEuler::~G4ImplicitEuler() 62 G4ImplicitEuler::~G4ImplicitEuler()
62 { 63 {
63 delete [] dydxTemp; << 64 delete[] dydxTemp;
64 delete [] yTemp; << 65 delete[] yTemp;
65 } 66 }
66 67
67 ////////////////////////////////////////////// 68 //////////////////////////////////////////////////////////////////////
68 // 69 //
69 // DumbStepper <<
70 // 70 //
>> 71
71 void 72 void
72 G4ImplicitEuler::DumbStepper( const G4double y << 73 G4ImplicitEuler::DumbStepper( const G4double yIn[],
73 const G4double d << 74 const G4double dydx[],
74 G4double h << 75 G4double h,
75 G4double y << 76 G4double yOut[])
76 { 77 {
77 const G4int numberOfVariables = GetNumberOfV << 78 G4int i;
>> 79 const G4int numberOfVariables= GetNumberOfVariables();
78 80
79 // Initialise time to t0, needed when it is 81 // Initialise time to t0, needed when it is not updated by the integration.
80 // <<
81 yTemp[7] = yOut[7] = yIn[7]; // Better to 82 yTemp[7] = yOut[7] = yIn[7]; // Better to set it to NaN; // TODO
82 83
83 for( G4int i = 0; i < numberOfVariables; ++i << 84 for( i = 0; i < numberOfVariables; i++ )
84 { 85 {
85 yTemp[i] = yIn[i] + h*dydx[i] ; 86 yTemp[i] = yIn[i] + h*dydx[i] ;
86 } 87 }
87 88
88 RightHandSide(yTemp,dydxTemp); 89 RightHandSide(yTemp,dydxTemp);
89 90
90 for( G4int i = 0; i < numberOfVariables; ++i << 91 for( i = 0; i < numberOfVariables; i++ )
91 { 92 {
92 yOut[i] = yIn[i] + 0.5 * h * ( dydx[i] + d 93 yOut[i] = yIn[i] + 0.5 * h * ( dydx[i] + dydxTemp[i] );
93 } 94 }
94 95
95 return; << 96 return ;
96 } 97 }
97 98