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Sander, Oliver authoredSander, Oliver authored
rotationtest.cc 8.95 KiB
#include <config.h>
#include <iostream>
#include <array>
#include <dune/common/fmatrix.hh>
#include <dune/gfe/rotation.hh>
#include "valuefactory.hh"
using namespace Dune;
void testDDExp()
{
std::array<FieldVector<double,3>, 125> v;
int ct = 0;
double eps = 1e-4;
for (int i=-2; i<3; i++)
for (int j=-2; j<3; j++)
for (int k=-2; k<3; k++) {
v[ct][0] = i;
v[ct][1] = j;
v[ct][2] = k;
ct++;
}
for (size_t i=0; i<v.size(); i++) {
// Compute FD approximation of second derivative of exp
std::array<Dune::FieldMatrix<double,3,3>, 4> fdDDExp;
for (int j=0; j<3; j++) {
for (int k=0; k<3; k++) {
if (j==k) {
SkewMatrix<double,3> forward(v[i]);
forward.axial()[j] += eps;
Rotation<double,3> forwardQ = Rotation<double,3>::exp(forward);
SkewMatrix<double,3> center(v[i]);
Rotation<double,3> centerQ = Rotation<double,3>::exp(center);
SkewMatrix<double,3> backward(v[i]);
backward.axial()[j] -= eps;
Rotation<double,3> backwardQ = Rotation<double,3>::exp(backward);
for (int l=0; l<4; l++)
fdDDExp[l][j][j] = (forwardQ[l] - 2*centerQ[l] + backwardQ[l]) / (eps*eps);
} else {
SkewMatrix<double,3> ffV(v[i]); ffV.axial()[j] += eps; ffV.axial()[k] += eps;
SkewMatrix<double,3> fbV(v[i]); fbV.axial()[j] += eps; fbV.axial()[k] -= eps;
SkewMatrix<double,3> bfV(v[i]); bfV.axial()[j] -= eps; bfV.axial()[k] += eps;
SkewMatrix<double,3> bbV(v[i]); bbV.axial()[j] -= eps; bbV.axial()[k] -= eps;
Rotation<double,3> forwardForwardQ = Rotation<double,3>::exp(ffV);
Rotation<double,3> forwardBackwardQ = Rotation<double,3>::exp(fbV);
Rotation<double,3> backwardForwardQ = Rotation<double,3>::exp(bfV);
Rotation<double,3> backwardBackwardQ = Rotation<double,3>::exp(bbV);
for (int l=0; l<4; l++)
fdDDExp[l][j][k] = (forwardForwardQ[l] + backwardBackwardQ[l]
- forwardBackwardQ[l] - backwardForwardQ[l]) / (4*eps*eps);
}
}
}
// Compute analytical second derivative of exp
std::array<Dune::FieldMatrix<double,3,3>, 4> ddExp;
Rotation<double,3>::DDexp(v[i], ddExp);
for (int m=0; m<4; m++)
for (int j=0; j<3; j++)
for (int k=0; k<3; k++)
if ( std::abs(fdDDExp[m][j][k] - ddExp[m][j][k]) > eps) {
std::cout << "Error at v = " << v[i]
<< "[" << m << ", " << j << ", " << k << "] "
<< " fd: " << fdDDExp[m][j][k]
<< " analytical: " << ddExp[m][j][k] << std::endl;
}
}
}
void testRotation(Rotation<double,3> q)
{
// Make sure it really is a unit quaternion
q.normalize();
assert(std::abs(1-q.two_norm()) < 1e-12);
// Turn it into a matrix
FieldMatrix<double,3,3> matrix;
q.matrix(matrix);
// make sure it is an orthogonal matrix
if (std::abs(1-matrix.determinant()) > 1e-12 )
DUNE_THROW(Exception, "Expected determinant 1, but the computed value is " << matrix.determinant());
assert( std::abs( matrix[0]*matrix[1] ) < 1e-12 );
assert( std::abs( matrix[0]*matrix[2] ) < 1e-12 );
assert( std::abs( matrix[1]*matrix[2] ) < 1e-12 );
// Turn the matrix back into a quaternion, and check whether it is the same one
// Since the quaternions form a double covering of SO(3), we may either get q back
// or -q. We have to check both.
Rotation<double,3> newQ;
newQ.set(matrix);
Rotation<double,3> diff = newQ;
diff -= q;
Rotation<double,3> sum = newQ;
sum += q;
if (diff.infinity_norm() > 1e-12 && sum.infinity_norm() > 1e-12)
DUNE_THROW(Exception, "Backtransformation failed for " << q << ". ");
// //////////////////////////////////////////////////////
// Check the director vectors
// //////////////////////////////////////////////////////
for (int i=0; i<3; i++)
for (int j=0; j<3; j++)
assert( std::abs(matrix[i][j] - q.director(j)[i]) < 1e-12 );
// //////////////////////////////////////////////////////
// Check multiplication with another unit quaternion
// //////////////////////////////////////////////////////
for (int i=-2; i<2; i++)
for (int j=-2; j<2; j++)
for (int k=-2; k<2; k++) for (int l=-2; l<2; l++)
if (i!=0 || j!=0 || k!=0 || l!=0) {
Rotation<double,3> q2(Quaternion<double>(i,j,k,l));
q2.normalize();
// set up corresponding rotation matrix
FieldMatrix<double,3,3> q2Matrix;
q2.matrix(q2Matrix);
// q2 = q2 * q Quaternion multiplication
q2 = q2.mult(q);
// q2 = q2 * q Matrix multiplication
q2Matrix.rightmultiply(matrix);
FieldMatrix<double,3,3> productMatrix;
q2.matrix(productMatrix);
// Make sure we got identical results
productMatrix -= q2Matrix;
assert(productMatrix.infinity_norm() < 1e-10);
}
// ////////////////////////////////////////////////////////////////
// Check the operators 'B' that create an orthonormal basis of H
// ////////////////////////////////////////////////////////////////
Quaternion<double> Bq[4];
Bq[0] = q;
Bq[1] = q.B(0);
Bq[2] = q.B(1);
Bq[3] = q.B(2);
for (int i=0; i<4; i++) {
for (int j=0; j<4; j++) {
double prod = Bq[i]*Bq[j];
assert( std::abs( prod - (i==j) ) < 1e-6 );
}
}
//////////////////////////////////////////////////////////////////////
// Check whether the derivativeOfMatrixToQuaternion methods works
//////////////////////////////////////////////////////////////////////
Tensor3<double,4,3,3> derivative = Rotation<double,3>::derivativeOfMatrixToQuaternion(matrix);
const double eps = 1e-8;
Tensor3<double,4,3,3> derivativeFD;
for (size_t i=0; i<3; i++)
{
for (size_t j=0; j<3; j++)
{
auto forwardMatrix = matrix;
forwardMatrix[i][j] += eps;
auto backwardMatrix = matrix;
backwardMatrix[i][j] -= eps;
Rotation<double,3> forwardRotation, backwardRotation;
forwardRotation.set(forwardMatrix);
backwardRotation.set(backwardMatrix);
for (size_t k=0; k<4; k++)
derivativeFD[k][i][j] = (forwardRotation.globalCoordinates()[k] - backwardRotation.globalCoordinates()[k]) / (2*eps);
}
}
if ((derivative - derivativeFD).infinity_norm() > 1e-6)
{
std::cout << "At matrix:\n" << matrix << std::endl;
std::cout << "Derivative of matrix to quaternion map does not match its FD approximation" << std::endl;
std::cout << "Analytical derivative:" << std::endl;
std::cout << derivative << std::endl;
std::cout << "Finite difference approximation" << std::endl;
std::cout << derivativeFD << std::endl;
abort();
}
}
//! test interpolation between two rotations
bool testInterpolation(const Rotation<double, 3>& a, const Rotation<double, 3>& b) {
// Compute difference on T_a SO(3)
Rotation<double, 3> newB = Rotation<double, 3>::interpolate(a, b, 1.0);
// Compare matrix representation
FieldMatrix<double, 3, 3> matB;
b.matrix(matB);
FieldMatrix<double, 3, 3> matNewB;
newB.matrix(matNewB);
matNewB -= matB;
if (matNewB.infinity_norm() > 1e-14)
std::cout << " Interpolation failed with difference " << matNewB.infinity_norm() << std::endl;
return (matNewB.infinity_norm() < 1e-14);
}
int main (int argc, char *argv[]) try
{
std::vector<Rotation<double,3> > testPoints;
ValueFactory<Rotation<double,3> >::get(testPoints);
int nTestPoints = testPoints.size();
// Test each element in the list
for (int i=0; i<nTestPoints; i++)
testRotation(testPoints[i]);
bool passed(true);
// Test interpolating between pairs of rotations
for (int i=0; i<nTestPoints-1; i++)
passed = passed and testInterpolation(testPoints[i], testPoints[i+1]);
// //////////////////////////////////////////////
// Test second derivative of exp
// //////////////////////////////////////////////
testDDExp();
return not passed;
} catch (Exception& e) {
std::cout << e.what() << std::endl;
}