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103 lines
2.4 KiB
103 lines
2.4 KiB
2 years ago
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/*=========================================================================
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Program: Visualization Toolkit
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Module: $RCSfile: vtkRungeKutta2.cxx,v $
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Copyright (c) Ken Martin, Will Schroeder, Bill Lorensen
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All rights reserved.
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See Copyright.txt or http://www.kitware.com/Copyright.htm for details.
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This software is distributed WITHOUT ANY WARRANTY; without even
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the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
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PURPOSE. See the above copyright notice for more information.
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=========================================================================*/
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#include "vtkRungeKutta2.h"
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#include "vtkFunctionSet.h"
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#include "vtkObjectFactory.h"
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vtkCxxRevisionMacro(vtkRungeKutta2, "$Revision: 1.14 $");
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vtkStandardNewMacro(vtkRungeKutta2);
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vtkRungeKutta2::vtkRungeKutta2()
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{
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}
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vtkRungeKutta2::~vtkRungeKutta2()
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{
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}
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// Calculate next time step
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int vtkRungeKutta2::ComputeNextStep(double* xprev, double* dxprev, double* xnext,
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double t, double& delT, double& delTActual,
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double, double, double, double& error)
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{
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int i, numDerivs, numVals;
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delTActual = delT;
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error = 0.0;
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if (!this->FunctionSet)
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{
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vtkErrorMacro("No derivative functions are provided!");
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return NOT_INITIALIZED;
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}
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if (!this->Initialized)
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{
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vtkErrorMacro("Integrator not initialized!");
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return NOT_INITIALIZED;
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}
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numDerivs = this->FunctionSet->GetNumberOfFunctions();
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numVals = numDerivs + 1;
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for(i=0; i<numVals-1; i++)
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{
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this->Vals[i] = xprev[i];
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}
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this->Vals[numVals-1] = t;
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// Obtain the derivatives dx_i at x_i
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if (dxprev)
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{
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for(i=0; i<numDerivs; i++)
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{
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this->Derivs[i] = dxprev[i];
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}
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}
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else if ( !this->FunctionSet->FunctionValues(this->Vals, this->Derivs) )
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{
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memcpy(xnext, this->Vals, (numVals-1)*sizeof(double));
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return OUT_OF_DOMAIN;
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}
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// Half-step
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for(i=0; i<numVals-1; i++)
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{
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this->Vals[i] = xprev[i] + delT/2.0*this->Derivs[i];
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}
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this->Vals[numVals-1] = t + delT/2.0;
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// Obtain the derivatives at x_i + dt/2 * dx_i
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if (!this->FunctionSet->FunctionValues(this->Vals, this->Derivs))
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{
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memcpy(xnext, this->Vals, (numVals-1)*sizeof(double));
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return OUT_OF_DOMAIN;
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}
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// Calculate x_i using improved values of derivatives
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for(i=0; i<numDerivs; i++)
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{
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xnext[i] = xprev[i] + delT*this->Derivs[i];
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}
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return 0;
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}
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