Fix regression in changeset f05dea6b2326836e5e0243fbaffbece84b833d64

: computeFromHessenberg can take any expression for matrixQ, not only an HouseholderSequence.

1 files changed, 9 insertions, 4 deletions

diff --git a/Eigen/src/Eigenvalues/RealSchur.h b/Eigen/src/Eigenvalues/RealSchur.h
index 4c53344bb..aca8a8279 100644
--- a/Eigen/src/Eigenvalues/RealSchur.h
+++ b/Eigen/src/Eigenvalues/RealSchur.h
@@ -270,8 +270,13 @@ RealSchur<MatrixType>& RealSchur<MatrixType>::compute(const EigenBase<InputType>
   // Step 1. Reduce to Hessenberg form
   m_hess.compute(matrix.derived()/scale);
 
-  // Step 2. Reduce to real Schur form  
-  computeFromHessenberg(m_hess.matrixH(), m_hess.matrixQ(), computeU);
+  // Step 2. Reduce to real Schur form
+  // Note: we copy m_hess.matrixQ() into m_matU here and not in computeFromHessenberg
+  //       to be able to pass our working-space buffer for the Householder to Dense evaluation.
+  m_workspaceVector.resize(matrix.cols());
+  if(computeU)
+    m_hess.matrixQ().evalTo(m_matU, m_workspaceVector);
+  computeFromHessenberg(m_hess.matrixH(), m_matU, computeU);
 
   m_matT *= scale;
   
@@ -285,8 +290,8 @@ RealSchur<MatrixType>& RealSchur<MatrixType>::computeFromHessenberg(const HessMa
 
   m_matT = matrixH;
   m_workspaceVector.resize(m_matT.cols());
-  if(computeU)
-    matrixQ.evalTo(m_matU, m_workspaceVector);
+  if(computeU && !internal::is_same_dense(m_matU,matrixQ))
+    m_matU = matrixQ;
   
   Index maxIters = m_maxIters;
   if (maxIters == -1)