[eigen] eigen matrix type :: value_type problem

[Brad Bell <bradbell@xxxxxxxxxx>]

As discussed below, many vector types use
    vector_type::value_type
for the type of the elements of a vector.

The CppAD EIGEN_MATRIXBASE_PLUGIN has the following code
    typedef Scalar value_type;
so that eigen vectors have this property.

This seems to cause problems with sparse matrices (see below).

Is there a way around this problem ?

-------- Forwarded Message --------

Subject:	Re: [CppAD] filling Eigen sparse matrix in presence of CppAD
Date:	Thu, 18 Dec 2014 05:25:54 -0700
From:	Brad Bell <bradbell@xxxxxxxxxx>
To:	cppad@xxxxxxxxxxxxxxxx, Mic >> Braun, Michael <braunm@xxxxxxxxxxxx>

Using  g++ 4.8.3,  if you delete
    typedef Scalar value_type;
at line 24 of
    https://projects.coin-or.org/CppAD/browser/trunk/cppad/example/eigen_plugin.hpp
the error in compiling the example below goes away.

CppAD expects
    Vector::value_type
to be the type of the elements of a vector; see
    http://www.coin-or.org/CppAD/Doc/simplevector.xml#Value%20Type

This is the same as for the C++ standard vector; as can be seen by searching for value_type on
    http://www.cplusplus.com/reference/vector/vector/

I wanted to ask about this on the eigen user's list
    http://listengine.tuxfamily.org/lists.tuxfamily.org/eigen/2014/12/maillist.html
but I did not see your posting there.

Brad


On 12/17/2014 11:33 AM, Braun, Michael wrote:

I posted this same question on the Eigen forum because I do not know if it is really an Eigen issue or a CppAD issue.

As part of a larger application that uses CppAD, I am trying to fill an Eigen sparse matrix.  The following MWE does not use CppAD, and when the first line (#define EIGEN_MATRIX_PLUGIN ... ) is commented out, this code runs fine.  

#define EIGEN_MATRIX_PLUGIN <cppad/example/eigen_plugin.hpp>

#include <Eigen/Eigen>

#include <Eigen/Sparse>

#include <cppad/cppad.hpp>

#include <cppad/example/cppad_eigen.hpp>

void triptest () {

  typedef Eigen::Triplet<double> TT;

  int n = 5;

  std::vector<TT> trips; 

  Eigen::SparseMatrix<double> M(n,n);

  

  for (int i=0; i<n; i++) {   

    trips.push_back (TT(i,i,i*i));

  }

  M.setFromTriplets(trips.begin(), trips.end());

  std::cout << M << "\n";

  

}

int main (void)

{   

  triptest();

  return 0;

}

But when left in, I get the following compile error:

 $ clang++ -I/opt/cppad/include -I$R_HOME/library/RcppEigen/include trips.cpp -o trips.so

In file included from trips.cpp:4:

In file included from .../Eigen/Sparse:19:

In file included from .../Eigen/SparseCore:40:

/Library/Frameworks/R.framework/Resources/library/RcppEigen/include/Eigen/src/SparseCore/SparseMatrix.h:957:11: error: 

      call to member function 'reserve' is ambiguous

    trMat.reserve(wi);

    ~~~~~~^~~~~~~

.../Eigen/src/SparseCore/SparseMatrix.h:1013:13: note: 

      in instantiation of function template specialization

      'Eigen::internal::set_from_triplets<std::__1::__wrap_iter<Eigen::Triplet<double, int> *>,

      Eigen::SparseMatrix<double, 0, int> >' requested here

  internal::set_from_triplets(begin, end, *this);

            ^

trips.cpp:18:5: note: in instantiation of function template specialization 'Eigen::SparseMatrix<double, 0,

      int>::setFromTriplets<std::__1::__wrap_iter<Eigen::Triplet<double, int> *> >' requested here

  M.setFromTriplets(trips.begin(), trips.end());

    ^

.../Eigen/src/SparseCore/SparseMatrix.h:270:17: note: 

      candidate function [with SizesType = Eigen::Matrix<int, -1, 1, 0, -1, 1>]

    inline void reserve(const SizesType& reserveSizes, const typename SizesType::value_type& enableif = typenam...

                ^

.../Eigen/src/SparseCore/SparseMatrix.h:276:17: note: 

      candidate function [with SizesType = Eigen::Matrix<int, -1, 1, 0, -1, 1>]

    inline void reserve(const SizesType& reserveSizes, const typename SizesType::Scalar& enableif =

                ^

.../Eigen/src/SparseCore/SparseMatrix.h:256:17: note: 

      candidate function not viable: no known conversion from 'Matrix<Index, Dynamic, 1>' to 'Index' (aka 'int') for 1st

      argument

    inline void reserve(Index reserveSize)

                ^

Any idea what's going on?  I have been able to narrow the problem directly to that first #define.  Also, this appears to happen only with EIGEN_MATRIX_PLUGIN, and not ARRAY or SPARSEMATRIX.

Thanks,

Michael

--------------------------

Michael Braun

Associate Professor of Marketing

Cox School of Business

Southern Methodist University

Dallas, TX 75275

braunm@xxxxxxx

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