Re: [eigen] Missing operator definition in Sparse?

[Gael Guennebaud <gael.guennebaud@xxxxxxxxx>]

implemented and committed as a standard sparse expression.

cheers,

gael

On Fri, Jun 25, 2010 at 12:31 AM, Sameer Agarwal
<sameeragarwal@xxxxxxxxxx> wrote:
> Hi Gael,
>
> x*y^T where one of the vectors is dense and one is sparse should
> return a sparse matrix.
> m.col(0) is a large but extremely sparse vector, so creating a dense
> temporary is a bad idea.
> Such rank 1 updates are not that uncommon.  I encounter this one
> while constructing a preconditioner.
>
> I can solve the problem by making both the vectors sparse, but I would
> argue that the mixed version should also work.
>
> Sameer
>
>
>
>
>
> On Thu, Jun 24, 2010 at 1:51 PM, Gael Guennebaud
> <gael.guennebaud@xxxxxxxxx> wrote:
>> On Thu, Jun 24, 2010 at 10:07 PM, Sameer Agarwal
>> <sameeragarwal@xxxxxxxxxx> wrote:
>>> Hi Guys,
>>>
>>> I am using the development branch. The following bit of code  does not compile.
>>>
>>> #include "Eigen/Core"
>>> #include "Eigen/Sparse"
>>>
>>> typedef Eigen::SparseMatrix<double, Eigen::ColMajor> SparseCol;
>>> typedef Eigen::Matrix<double, Eigen::Dynamic, 1> Vector;
>>>
>>> int main() {
>>>  int nrow = 5;
>>>  int ncol = 5;
>>>  SparseCol m(nrow,ncol);
>>>  Vector x(ncol,1);
>>>  SparseCol A = m.subcols(1, 4) - m.col(0)* x.transpose();
>>>  return 0;
>>> }
>>>
>>> Compiled complains about a missing operator definition.
>>
>> Indeed, there is no special handling for m.col(0)* x.transpose(). It
>> is treated as a standard sparse by dense product, and so it returns a
>> dense object...
>>
>> To be honest I'm a bit surprised by such an expression, but if you
>> need it that's easily doable.
>>
>> As a side note, the following works but fully evaluate the outer
>> product to a dense temporary matrix:
>>
>> Vector x(4,1);
>> SparseCol A = m.subcols(1, 4) - (m.col(0)* x.transpose()).sparseView();
>>
>> (you need to update your local copy to make it compile fine)
>>
>> gael
>>
>>>
>>>
>>> test_sparse.cc: In function ‘int main()’:
>>> test_sparse.cc:12: error: no match for ‘operator-’ in
>>> ‘m.Eigen::SparseMatrix<double, 0,
>>> int>::<anonymous>.Eigen::SparseMatrixBase<Derived>::subcols [with
>>> Derived = Eigen::SparseMatrix<double, 0, int>](1, 4) -
>>> Eigen::SparseMatrixBase<Derived>::operator*(const
>>> Eigen::MatrixBase<OtherDerived>&) const [with OtherDerived =
>>> Eigen::Transpose<Eigen::Matrix<double, -0x00000000000000001, 1, 0,
>>> -0x00000000000000001, 1> >, Derived =
>>> Eigen::SparseInnerVectorSet<Eigen::SparseMatrix<double, 0, int>,
>>> 1>](((const Eigen::MatrixBase<Eigen::Transpose<Eigen::Matrix<double,
>>> -0x00000000000000001, 1, 0, -0x00000000000000001, 1> > >&)((const
>>> Eigen::MatrixBase<Eigen::Transpose<Eigen::Matrix<double,
>>> -0x00000000000000001, 1, 0, -0x00000000000000001, 1> >
>>>>*)(&((Eigen::DenseBase<Eigen::Matrix<double, -0x00000000000000001, 1,
>>> 0, -0x00000000000000001, 1> >*)(&
>>> x))->Eigen::DenseBase<Derived>::transpose [with Derived =
>>> Eigen::Matrix<double, -0x00000000000000001, 1, 0,
>>> -0x00000000000000001, 1>]()))))’
>>> Eigen/src/Sparse/../plugins/CommonCwiseUnaryOps.h:59: note: candidates
>>> are: const Eigen::CwiseUnaryOp<Eigen::ei_scalar_opposite_op<typename
>>> Eigen::ei_traits<Derived>::Scalar>, Derived>
>>> Eigen::SparseMatrixBase<Derived>::operator-() const [with Derived =
>>> Eigen::SparseInnerVectorSet<Eigen::SparseMatrix<double, 0, int>,
>>> -0x00000000000000001>]
>>>
>>> Thanks,
>>> Sameer
>>>
>>>
>>>
>>
>>
>>
>
>
>