Re: [eigen] Eigen 3.0-beta1 operator+= problem

[Benoit Jacob <jacob.benoit.1@xxxxxxxxx>]

Problem confirmed with current development branch.

gdb tells me it's picking up the operator+= defined at
Eigen/src/Core/CwiseBinaryOp.h:232:

template<typename Derived>
template<typename OtherDerived>
EIGEN_STRONG_INLINE Derived &
MatrixBase<Derived>::operator+=(const MatrixBase<OtherDerived>& other)
{
  SelfCwiseBinaryOp<ei_scalar_sum_op<Scalar>, Derived, OtherDerived>
tmp(derived());
  tmp = other.derived();
  return derived();
}

So this is likely a bug in SelfCwiseBinaryOp. That's all I can do for today....

Benoit

2010/9/5 Gavin Band <gavin.band@xxxxxxxxxxxxx>:
> Dear Eigen list,
>
> I decided to evaluate Eigen and (wanting to dive in at the deep end) downloaded Eigen 3.0 beta.  However, I immediately ran into the problem exemplified by the code below, in which using operator+= seems to give a different answer than using operators + and = separately when the rhs is the result of ColPivHouseholderQR::solve().  (The problem did not occur with a plain MatrixXd on the right.)  Is this behaviour a bug, or am I doing something wrong?
>
> Many thanks,
> Gavin Band.
>
> // ==== begin code ====
>
> #include <iostream>
> #include <Eigen/Dense>
>
> int main()
> {
>    Eigen::VectorXd pt( 1 ), v1( 1 ), v2( 1 ) ;
>    pt << 1 ;
>    v1 << 1 ;
>    v2 << 1 ;
>
>    Eigen::MatrixXd M( 1, 1 ) ;
>    M << 1.0 ;
>
>    Eigen::ColPivHouseholderQR< Eigen::MatrixXd > decomposer( M ) ;
>
>    v1 += decomposer.solve( pt ) ;      //  value is 1 ???
>    v2 = v2 + decomposer.solve( pt ) ;  //  value is 2, ok.
>
>    std::cerr << "QR = " << decomposer.matrixQR() << ", v1 = " << v1 << ", v2 = " << v2 << ".\n" ;
> }
>
>
>
>
>