Re: [eigen] Vectorwise dot product feature request

[Johan Pauwels <johan.pauwels@xxxxxxxxxxxxx>]

On 2010-07-07 15:40, Gael Guennebaud wrote:
> actually, this is more subtle :) When an inner product is detected, it
> returns an InnerProduct object which can be converted into a scalar
> type:
>    

Interesting explanation, thanks.

I have another vectorwise question/request. I'd like to broadcast a 
coefficient-wise product like "mat.array().colwise() *= vec.array()". Is 
it possible to do this now? Or will it be in the future?

Kind regards,
Johan
> On Wed, Jul 7, 2010 at 2:46 PM, Márton Danóczy<marton78@xxxxxxxxxx>  wrote:
>    
> > Because .dot() returns a scalar, whereas multiplication returns an 1x1 matrix.
> >
> > Marton
> >
> >
> >
> > On 7 July 2010 14:15, Johan Pauwels<johan.pauwels@xxxxxxxxxxxxx>  wrote:
> >      
> > > On 2010-07-07 13:02, Aron Ahmadia wrote:
> > >
> > > That looks suspiciously like a transposed multiply to me...
> > >
> > > Ugh, exactly. Sorry for the bother. My mind was so set on a collection of
> > > independent columns and broadcasting operations, that I forgot the basic
> > > matrix multiplication. One might wonder why there even is a .dot() syntax?
> > >
> > > Regards,
> > > Johan
> > >
> > > A
> > >
> > > On Wed, Jul 7, 2010 at 1:59 PM, Johan Pauwels<johan.pauwels@xxxxxxxxxxxxx>
> > > wrote:
> > >        
> > > > Hello all,
> > > >
> > > > Would it be possible to allow a vectorwise dot product as in the example
> > > > below?
> > > >
> > > > #include<Eigen/Core>
> > > >
> > > > int main()
> > > > {
> > > >     Eigen::MatrixXf mat = Eigen::MatrixXf::Random(5,2);
> > > >     Eigen::VectorXf vec = Eigen::VectorXf::Random(5);
> > > >     Eigen::RowVectorXf result(2);
> > > >
> > > >     // this syntax
> > > >     result = mat.colwise().dot(vec);
> > > >     // instead of this for loop
> > > >     for (int i = 0; i<  mat.cols(); ++i)
> > > >     {
> > > >         result[i] = mat.col(i).dot(vec);
> > > >     }
> > > > }
> > > >
> > > > Regards,
> > > > Johan
> > > >
> > > >
> > > >          
> > >
> > >
> > >        
> >
> >
> >      
>
>