Why does calling .row() method on ColMajor MappedSparseMatrix fail?

Question

Here is my code:

#include <iostream>
#include <Eigen/Sparse>

using namespace Eigen;

int main()
{
  int n_rows=4, n_cols=3, nnz=5;
  int outer_index[] = {0,1,3,5};
  int inner_index[] = {0,2,3,1,2};
  double values[] = {1,1,1,1,1};

  MappedSparseMatrix<double> u2i(n_rows, n_cols, nnz, outer_index, inner_index, values);

  std::cout << u2i << std::endl;
  std::cout << u2i.col(1) << std::endl; // works fine
  //std::cout << u2i.row(1) << std::endl; // fails
  return 0;
}

This is the error message I get when I try std::cout << u2i.row(1) << std::endl;

my_exec: /usr/include/Eigen/src/Core/util/XprHelper.h:53: Eigen::internal::variable_if_dynamic::variable_if_dynamic(T) [with T = int; int Value = 1]: Assertion `v == T(Value)' failed. Aborted (core dumped)

It seems that the issue is calling .row() on the ColMajor matrix; however, I don't see why this should cause an error, or then why is .row() method is allowed at all?

If I am not missing anything in my implementation, what's going on here?

I am using Eigen 3.2.2.

Edit:

Apparently this also fails with SparseMatrix as well.

#include <Eigen/Sparse>
#include <Eigen/Dense>
#include <iostream>

int main()
{
  using namespace Eigen;
  Matrix<int64_t, Dynamic, Dynamic> temp(6, 5);
  temp <<  0, 1, 0, 3, 4,
         0, 1, 0, 0, 0,
         0, 0, 0, 0, 0,
         2, 1, 0, 0, 3,
         0, 2, 0, 0, 1,
         1, 0, 0, 1, 0;

  SparseMatrix<int64_t> temp_sparse = temp.sparseView();

  std::cout << temp_sparse.row(5) << std::endl;
  return 0;
}

Error message (same):

test_calc_top_actions.exe: /usr/include/eigen3/Eigen/src/Core/util/XprHelper.h:53: Eigen::internal::variable_if_dynamic::variable_if_dynamic(T) [with T = int; int Value = 1]: Assertion `v == T(Value)' failed. Aborted

Answer 1

This code still fails at runtime with the latest release (3.2.4). The bug was reported here and a fix is already available upstream (but not released yet).