I am trying to multiply a sparse matrix by a dense one:

#include <Eigen/Dense>
#include <Eigen/Sparse>

using namespace Eigen;

int main()
{
SparseMatrix<double> s;
s.resize(3,3);
MatrixXf d(3,3);

MatrixXf d2(3,3);

// gives an error
s*d;

// doesn't give an error
d*d2;
}

This MWE compiles perfectly without s*d, but with s*d there are many template errors... Any ideas how to do that?

Thanks.

you are mixing float and double! Either use MatrixXd or a SparseMatrix<float> to ensure compatible scalar types. You can also explicitly cast to a given scalar type using d.cast<double>(), e.g.:

s * d.cast<double>()