CSRMatrix::setValue does not update isSorted causing wrong results when accessing values

[bernlu]

The internal flag isSorted (tracks whether each row in the columnIdx vector is sorted) is not consistent with the actual state of the columnIdx vector. Inserting new values with setValue does not always keep the vector sorted, but will never update the state of isSorted. This causes incorrect results when accessing values with CSRMatrix(i,j).

Small example:

CSRMatrix A(2);
A.setValue(0, 0, 1);
A.setValue(0, 1, -1);
A.setValue(1, 0, -1);
A.setValue(1, 1, 1);
// A =
// 1 -1
// -1 1
for (index i = 0; i < A.numberOfRows(); i++) {
    for (index j = 0; j < A.numberOfColumns(); j++)
        std::cout << A(i, j) << ", ";
    std::cout << std::endl;
}

Output:

0, -1,
0, 1,