File: vtkRungeKutta2.cxx

package info (click to toggle)
vtk 5.8.0-13
  • links: PTS, VCS
  • area: main
  • in suites: wheezy
  • size: 130,524 kB
  • sloc: cpp: 1,129,256; ansic: 708,203; tcl: 48,526; python: 20,875; xml: 6,779; yacc: 4,208; perl: 3,121; java: 2,788; lex: 931; sh: 660; asm: 471; makefile: 299
file content (101 lines) | stat: -rw-r--r-- 2,418 bytes parent folder | download | duplicates (4)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
/*=========================================================================

  Program:   Visualization Toolkit
  Module:    vtkRungeKutta2.cxx

  Copyright (c) Ken Martin, Will Schroeder, Bill Lorensen
  All rights reserved.
  See Copyright.txt or http://www.kitware.com/Copyright.htm for details.

     This software is distributed WITHOUT ANY WARRANTY; without even
     the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
     PURPOSE.  See the above copyright notice for more information.

=========================================================================*/
#include "vtkRungeKutta2.h"

#include "vtkFunctionSet.h"
#include "vtkObjectFactory.h"

vtkStandardNewMacro(vtkRungeKutta2);

vtkRungeKutta2::vtkRungeKutta2() 
{
}

vtkRungeKutta2::~vtkRungeKutta2() 
{
}

// Calculate next time step
int vtkRungeKutta2::ComputeNextStep(double* xprev, double* dxprev, double* xnext, 
                                    double t, double& delT, double& delTActual,
                                    double, double, double, double& error)
{
  int i, numDerivs, numVals;

  delTActual = delT;
  error = 0.0;

  if (!this->FunctionSet)
    {
    vtkErrorMacro("No derivative functions are provided!");
    return NOT_INITIALIZED;
    }

  if (!this->Initialized)
    {
    vtkErrorMacro("Integrator not initialized!");
    return NOT_INITIALIZED;
    }
  
  numDerivs = this->FunctionSet->GetNumberOfFunctions();
  numVals = numDerivs + 1;
  for(i=0; i<numVals-1; i++)
    {
    this->Vals[i] = xprev[i];
    }
  this->Vals[numVals-1] = t;

  // Obtain the derivatives dx_i at x_i
  if (dxprev)
    {
    for(i=0; i<numDerivs; i++)
      {
      this->Derivs[i] = dxprev[i];
      }
    }
  else if ( !this->FunctionSet->FunctionValues(this->Vals, this->Derivs) )
    {
    memcpy(xnext, this->Vals, (numVals-1)*sizeof(double));
    return OUT_OF_DOMAIN;
    }

  // Half-step
  for(i=0; i<numVals-1; i++)
    {
    this->Vals[i] = xprev[i] + delT/2.0*this->Derivs[i];
    }
  this->Vals[numVals-1] = t + delT/2.0;

  // Obtain the derivatives at x_i + dt/2 * dx_i
  if (!this->FunctionSet->FunctionValues(this->Vals, this->Derivs))
    {
    memcpy(xnext, this->Vals, (numVals-1)*sizeof(double));
    return OUT_OF_DOMAIN;
    }
    
  // Calculate x_i using improved values of derivatives
  for(i=0; i<numDerivs; i++)
    {
    xnext[i] = xprev[i] + delT*this->Derivs[i];
    }

  return 0;
}