Fix SparseQR::rank for a completely empty matrix.

1 files changed, 4 insertions, 2 deletions

diff --git a/Eigen/src/SparseQR/SparseQR.h b/Eigen/src/SparseQR/SparseQR.h
index f6a9af672..879ac553d 100644
--- a/Eigen/src/SparseQR/SparseQR.h
+++ b/Eigen/src/SparseQR/SparseQR.h
@@ -378,6 +378,8 @@ void SparseQR<MatrixType,OrderingType>::factorize(const MatrixType& mat)
   {
     RealScalar max2Norm = 0.0;
     for (int j = 0; j < n; j++) max2Norm = (max)(max2Norm, m_pmat.col(j).norm());
+    if(max2Norm==RealScalar(0))
+      max2Norm = RealScalar(1);
     pivotThreshold = 20 * (m + n) * max2Norm * NumTraits<RealScalar>::epsilon();
   }
   
@@ -386,7 +388,7 @@ void SparseQR<MatrixType,OrderingType>::factorize(const MatrixType& mat)
   
   Index nonzeroCol = 0; // Record the number of valid pivots
   m_Q.startVec(0);
-  
+
   // Left looking rank-revealing QR factorization: compute a column of R and Q at a time
   for (Index col = 0; col < n; ++col)
   {
@@ -554,7 +556,7 @@ void SparseQR<MatrixType,OrderingType>::factorize(const MatrixType& mat)
   m_R.finalize();
   m_R.makeCompressed();
   m_isQSorted = false;
-  
+
   m_nonzeropivots = nonzeroCol;
   
   if(nonzeroCol<n)