Created attachment 454 [details] source code to reproduce the problem When I compile and run the attached program, which constructs a 2x2 sparse matrix of doubles and attempts to perform a QR factorization, I get the following output: Nonzero entries: (_,_) (_,_) (0.5,1) (_,_) Outer pointers: 0 2 $ Inner non zeros: 0 1 $ 0 0 0 0.5 a.out: eigen/Eigen/src/Core/DenseCoeffsBase.h:412: Eigen::DenseCoeffsBase<Derived, 1>::Scalar& Eigen::DenseCoeffsBase<Derived, 1>::operator()(Eigen::DenseCoeffsBase<Derived, 1>::Index) [with Derived = Eigen::Matrix<int, -0x00000000000000001, 1>, Eigen::DenseCoeffsBase<Derived, 1>::Scalar = int, Eigen::DenseCoeffsBase<Derived, 1>::Index = long int]: Assertion `index >= 0 && index < size()' failed. Aborted (core dumped) If I run the program under valgrind, I get some reports about uninitialized memory: ==20561== Conditional jump or move depends on uninitialised value(s) ==20561== at 0x515C8A8: sqrt (w_sqrt.c:28) ==20561== by 0x404D84: Eigen::SparseMatrixBase<Eigen::Block<Eigen::SparseMatrix<double, 0, int>, -1, 1, true> >::norm() const (SparseDot.h:90) ==20561== by 0x402B18: Eigen::SparseQR<Eigen::SparseMatrix<double, 0, int>, Eigen::NaturalOrdering<int> >::factorize(Eigen::SparseMatrix<double, 0, int> const&) (SparseQR.h:332) ==20561== by 0x401FC3: Eigen::SparseQR<Eigen::SparseMatrix<double, 0, int>, Eigen::NaturalOrdering<int> >::compute(Eigen::SparseMatrix<double, 0, int> const&) (SparseQR.h:87) ==20561== by 0x400FCB: main (bug135.cpp:19)
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