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Bug 734 - Spline Module: A call to Spline::derivative fails to compile if dimension=1
Summary: Spline Module: A call to Spline::derivative fails to compile if dimension=1
Alias: None
Product: Eigen
Classification: Unclassified
Component: Unsupported modules (show other bugs)
Version: 3.2
Hardware: All All
: Normal Unknown
Assignee: Hauke Heibel
Depends on:
Reported: 2014-01-30 23:15 UTC by Philipp Büttgenbach
Modified: 2015-06-24 17:11 UTC (History)
2 users (show)

Bug demonstration programm and patch for fixing the bug (10.00 KB, application/x-tar)
2014-01-30 23:15 UTC, Philipp Büttgenbach
no flags Details
patch (5.64 KB, text/html)
2015-06-24 17:11 UTC, Alice
no flags Details

Description Philipp Büttgenbach 2014-01-30 23:15:51 UTC
Created attachment 418 [details]
Bug demonstration programm and patch for fixing the bug

Dear Maintainer,

the bug can be demonstrated using Hauke's example from (see enclosed file). The call to
Spline2d::derivative<1> is an extension of Hauke's example inserted
by me.  This call makes this example fail to compile:

$ LANG=C g++ -I/usr/include/eigen3/ eigen-spline-example-from-hauke.cpp
In file included from /usr/include/eigen3/Eigen/Core:300:0,
                 from eigen-spline-example-from-hauke.cpp:4:
/usr/include/eigen3/Eigen/src/Core/PlainObjectBase.h: In instantiation of
'static void Eigen::PlainObjectBase<Derived>::_check_template_params() [with
Derived = Eigen::Array<double, 1, -1, 0, 1, 2>]':
/usr/include/eigen3/Eigen/src/Core/Array.h:127:7:   required from
'Eigen::Array<_Scalar, _Rows, _Cols, _Options, _MaxRows, _MaxCols>::Array()
[with _Scalar = double; int _Rows = 1; int _Cols = -1; int _Options = 0; int
_MaxRows = 1; int _MaxCols = 2]'
/usr/include/eigen3/unsupported/Eigen/src/Splines/Spline.h:339:70:   required
from 'typename Eigen::SplineTraits<Eigen::Spline<Scalar, Dim, Degree>,
DerivativeOrder>::DerivativeType Eigen::Spline<Scalar, Dim,
Degree>::derivatives(Eigen::Spline<Scalar, Dim, Degree>::Scalar,
Eigen::DenseIndex) const [with int DerivativeOrder = 1; _Scalar = double; int
_Dim = 1; int _Degree = -1; typename Eigen::SplineTraits<Eigen::Spline<Scalar,
Dim, Degree>, DerivativeOrder>::DerivativeType = Eigen::Array<double, 1, -1, 0,
1, 2>; Eigen::Spline<Scalar, Dim, Degree>::Scalar = double; Eigen::DenseIndex =
eigen-spline-example-from-hauke.cpp:37:98:   required from here
/usr/include/eigen3/Eigen/src/Core/PlainObjectBase.h:654:7: error:

This bug can be fixed by changing in
/usr/include/eigen3/unsupported/Eigen/src/Splines/SplineFwd.h the
DerivativeType from ColMajor to RowMajor (see enclosed patch for details).
With this change everything compiles fine:

$ LANG=C g++ -I/usr/include/eigen3/ -include SplineFwd.h eigen-spline-example-
from-hauke.cpp && echo $?
Comment 1 Christoph Hertzberg 2014-01-31 15:51:48 UTC
The only question is, if someone expects the return type to be column major if it has more than 1 row (or if it is slightly more efficient). This could be achieved by a simple `?:` expression.
I assign it to Hauke and let him decide ...
Comment 2 Hauke Heibel 2014-02-01 21:01:40 UTC
I pushed a fix (though under a misconfigured user name). I took your patch as a starting point and added two changes.

First, I did what Christoph suggested. I keep RowMajor order, if possible. The reason is to keep derivative values of the same order close to each other in memory. 

Second, I also added the fix the the second traits implementation.

Thanks for reporting the isssue and I am happy to see the somebody is using the code!

Comment 3 Alice 2015-06-24 17:11:32 UTC
Created attachment 586 [details]

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