* Draft of a eigenvalues solver

  (does not support complex and does not re-use the QR decomposition)

* Rewrite the cache friendly product to have only one instance per scalar type !
  This significantly speeds up compilation time and reduces executable size.
  The current drawback is that some trivial expressions might be
  evaluated like conjugate or negate.

* Renamed "cache optimal" to "cache friendly"

* Added the ability to directly access matrix data of some expressions via:
  - the stride()/_stride() methods
  - DirectAccessBit flag (replace ReferencableBit)

1 files changed, 4 insertions, 3 deletions

diff --git a/Eigen/src/QR/QR.h b/Eigen/src/QR/QR.h
index d0121cc7a..d42153eb9 100644
--- a/Eigen/src/QR/QR.h
+++ b/Eigen/src/QR/QR.h
@@ -95,10 +95,11 @@ void QR<MatrixType>::_compute(const MatrixType& matrix)
       m_qr(k,k) += 1.0;
 
       // apply transformation to remaining columns
-      for (int j = k+1; j < cols; j++)
+      int remainingCols = cols - k -1;
+      if (remainingCols>0)
       {
-        Scalar s = -(m_qr.col(k).end(remainingSize).transpose() * m_qr.col(j).end(remainingSize))(0,0) / m_qr(k,k);
-        m_qr.col(j).end(remainingSize) += s * m_qr.col(k).end(remainingSize);
+        m_qr.corner(BottomRight, remainingSize, remainingCols) -= (1./m_qr(k,k)) * m_qr.col(k).end(remainingSize)
+          * (m_qr.col(k).end(remainingSize).transpose() * m_qr.corner(BottomRight, remainingSize, remainingCols));
       }
     }
     m_norms[k] = -nrm;