This bugzilla service is closed. All entries have been migrated to https://gitlab.com/libeigen/eigen
Bug 997 - .hnormalized() produces compilation errors
Summary: .hnormalized() produces compilation errors
Status: RESOLVED FIXED
Alias: None
Product: Eigen
Classification: Unclassified
Component: Geometry (show other bugs)
Version: 3.2
Hardware: All All
: Normal Compilation Problem
Assignee: Nobody
URL:
Whiteboard:
Keywords:
Depends on:
Blocks: 3.3
  Show dependency treegraph
 
Reported: 2015-04-15 14:05 UTC by Sergiu Deitsch
Modified: 2019-12-04 14:31 UTC (History)
4 users (show)



Attachments

Description Sergiu Deitsch 2015-04-15 14:05:04 UTC
I have the following function, which is used in combination with ceres::Jet<> as scalar:

template
<
    class Derived1,
    class Derived2
>
inline Eigen::Matrix<typename Eigen::MatrixBase<Derived1>::Scalar, 2, 1> reproject(
        const Eigen::MatrixBase<Derived1>& pt,
        const Eigen::MatrixBase<Derived2>& W
    )
{
    return (W * pt.homogeneous()).hnormalized();
}

If I don't call .eval() before .hnormalized() this results in the following compilation error:

/usr/include/eigen3/Eigen/src/Core/DenseCoeffsBase.h:137:14: error: no viable conversion from 'const
      Eigen::ReturnByValue<Eigen::internal::homogeneous_left_product_impl<Eigen::Homogeneous<Eigen::Matrix<double, 2, 1, 0, 2, 1>, 0>, Eigen::Matrix<double, 3, 3, 0,
      3, 3> > >::YOU_ARE_TRYING_TO_ACCESS_A_SINGLE_COEFFICIENT_IN_A_SPECIAL_EXPRESSION_WHERE_THAT_IS_NOT_ALLOWED_BECAUSE_THAT_WOULD_BE_INEFFICIENT' to 'const double'
      return derived().coeff(index);
             ^~~~~~~~~~~~~~~~~~~~~~
/usr/include/eigen3/Eigen/src/Geometry/Homogeneous.h:163:40: note: in instantiation of member function
      'Eigen::DenseCoeffsBase<Eigen::ReturnByValue<Eigen::internal::homogeneous_left_product_impl<Eigen::Homogeneous<Eigen::Matrix<double, 2, 1, 0, 2, 1>, 0>,
      Eigen::Matrix<double, 3, 3, 0, 3, 3> > >, 0>::coeff' requested here
    ColsAtCompileTime==1?1:size()-1) / coeff(size()-1);


I'm using Clang 3.6 and Eigen 3.2.4.
Comment 1 Sergiu Deitsch 2015-04-15 14:53:59 UTC
By the way, this happens when using double as scalar as well.
Comment 2 Christoph Hertzberg 2015-04-15 19:03:28 UTC
The cleanest/most efficient workaround would be to store W as a Transform (and omit the homogeneous() and hnormalized() calls).
But I agree that your code should compile.
Comment 3 Sergiu Deitsch 2015-04-16 14:37:47 UTC
I don't see how storing W in a Transform can be more efficient. Wouldn't that still require to call .homogeneous() and .hnormalized(), would it?
Comment 4 Christoph Hertzberg 2015-04-16 19:45:11 UTC
(In reply to Sergiu Dotenco from comment #3)
> I don't see how storing W in a Transform can be more efficient. Wouldn't
> that still require to call .homogeneous() and .hnormalized(), would it?

I admit that I did not check the code. I wrongfully assumed, Transform * vector automatically normalizes when assigning to a vector of size dim (and not dim+1).
Comment 5 Gael Guennebaud 2015-04-16 20:24:14 UTC
Indeed, hnormalized should perform the call to eval for you.

In Eigen 3.3, evaluators should refactor this expression to:

(W.leftCols<2>() * pt + W.col(2)).hnormalized()

and, support for:

 W * lazyProduct( pt.homogeneous() )

has also to be added.
Comment 6 Gael Guennebaud 2015-06-08 13:45:03 UTC
Actually, this is already working fine in the devel branch.

The following changeset add support for lazyProduct:

https://bitbucket.org/eigen/eigen/commits/57baa6174354/
Changeset:   57baa6174354
User:        ggael
Date:        2015-06-08 13:43:41+00:00
Summary:     Bug 997: add missing evaluators for m.lazyProduct(v.homogeneous())

Backporting to 3.2 is impossible, so I vote for wontfix for 3.2 and fixed for the devel branch.
Comment 7 Nobody 2019-12-04 14:31:18 UTC
-- GitLab Migration Automatic Message --

This bug has been migrated to gitlab.com's GitLab instance and has been closed from further activity.

You can subscribe and participate further through the new bug through this link to our GitLab instance: https://gitlab.com/libeigen/eigen/issues/997.

Note You need to log in before you can comment on or make changes to this bug.