Re: [eigen] Vectorwise dot product feature request

```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

```
```

```
```

```
```
```
```

```

 Mail converted by MHonArc 2.6.19+ http://listengine.tuxfamily.org/