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fix bug #478: RealSchur failed on a zero matrix.

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This commit is contained in:
Gael Guennebaud 2012-06-20 10:08:32 +02:00
parent c8346abcdd
commit b96b429aa2
1 changed files with 31 additions and 29 deletions
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58
Eigen/src/Eigenvalues/RealSchur.h
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@ -239,38 +239,40 @@ RealSchur<MatrixType>& RealSchur<MatrixType>::compute(const MatrixType& matrix,
Scalar exshift(0); // sum of exceptional shifts Scalar exshift(0); // sum of exceptional shifts
Scalar norm = computeNormOfT(); Scalar norm = computeNormOfT();
while (iu >= 0) if(norm!=0)
{ {
Index il = findSmallSubdiagEntry(iu, norm); while (iu >= 0)
{
Index il = findSmallSubdiagEntry(iu, norm);
// Check for convergence // Check for convergence
if (il == iu) // One root found if (il == iu) // One root found
{ {
m_matT.coeffRef(iu,iu) = m_matT.coeff(iu,iu) + exshift; m_matT.coeffRef(iu,iu) = m_matT.coeff(iu,iu) + exshift;
if (iu > 0) if (iu > 0)
m_matT.coeffRef(iu, iu-1) = Scalar(0); m_matT.coeffRef(iu, iu-1) = Scalar(0);
iu--; iu--;
iter = 0; iter = 0;
} }
else if (il == iu-1) // Two roots found else if (il == iu-1) // Two roots found
{ {
splitOffTwoRows(iu, computeU, exshift); splitOffTwoRows(iu, computeU, exshift);
iu -= 2; iu -= 2;
iter = 0; iter = 0;
} }
else // No convergence yet else // No convergence yet
{ {
// The firstHouseholderVector vector has to be initialized to something to get rid of a silly GCC warning (-O1 -Wall -DNDEBUG ) // The firstHouseholderVector vector has to be initialized to something to get rid of a silly GCC warning (-O1 -Wall -DNDEBUG )
Vector3s firstHouseholderVector(0,0,0), shiftInfo; Vector3s firstHouseholderVector(0,0,0), shiftInfo;
computeShift(iu, iter, exshift, shiftInfo); computeShift(iu, iter, exshift, shiftInfo);
iter = iter + 1; iter = iter + 1;
if (iter > m_maxIterations) break; if (iter > m_maxIterations) break;
Index im; Index im;
initFrancisQRStep(il, iu, shiftInfo, im, firstHouseholderVector); initFrancisQRStep(il, iu, shiftInfo, im, firstHouseholderVector);
performFrancisQRStep(il, im, iu, computeU, firstHouseholderVector, workspace); performFrancisQRStep(il, im, iu, computeU, firstHouseholderVector, workspace);
}
} }
} }
if(iter <= m_maxIterations) if(iter <= m_maxIterations)
m_info = Success; m_info = Success;
else else