Re: [eigen] Array cwise multiplication
• To: eigen@xxxxxxxxxxxxxxxxxxx
• Subject: Re: [eigen] Array cwise multiplication
• From: Benoit Jacob <jacob.benoit.1@xxxxxxxxx>
• Date: Wed, 29 Sep 2010 11:37:27 -0700
• Domainkey-signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :content-type:content-transfer-encoding; b=nL82774U/NQiCiDDXP77zpDpdK29V79G837b6WV8EgLl0XQnhfrJAlkOVvNAruhuyt L217ya3GA4udwMDYsobcpdfAPWySujGCpO+8cHTmWmN4XglK3nrU/Z5E4ab3UQcKnBAr 0BCma7YYr0WI5rtz42a197e4HYHEDz/8Drko4=

```meanwhile you can do the same with a diagonal product:

a * b.asDiagonal()

or

b.asDiagonal() * a

2010/9/29 Carlos Becker <carlosbecker@xxxxxxxxx>:
> The strange things is that operator + and - work, but I guess that might
> come from Matrix. So there is something strange going on with array
> colwise() and rowwise() (just tested that too, very quick, and seems to have
> the same problems).
>
>
> On Wed, Sep 29, 2010 at 8:09 PM, Benoit Jacob <jacob.benoit.1@xxxxxxxxx>
> wrote:
>>
>> erm, ignore me, that didn't make sense.
>>
>> 2010/9/29 Benoit Jacob <jacob.benoit.1@xxxxxxxxx>:
>> > ah, i know.
>> >
>> > b is a column-vector. you can't multiply colwise by it.
>> >
>> > Either make it a row-vector or multiply rowwise by it.
>> >
>> > 2010/9/29 Carlos Becker <carlosbecker@xxxxxxxxx>:
>> >> I already tried that, and still doesn't work. I get the following error
>> >> (sorry for the flooding)
>> >> test.cpp:20: error: no match for ‘operator*’ in
>> >> ‘((Eigen::DenseBase<Eigen::ArrayWrapper<Eigen::Matrix<float,
>> >> -0x00000000000000001, -0x00000000000000001, 0, -0x00000000000000001,
>> >> -0x00000000000000001> > >*)(&((Eigen::MatrixBase<Eigen::Matrix<float,
>> >> -0x00000000000000001, -0x00000000000000001, 0, -0x00000000000000001,
>> >> -0x00000000000000001> >*)(& a))->Eigen::MatrixBase<Derived>::array
>> >> [with
>> >> Derived = Eigen::Matrix<float, -0x00000000000000001,
>> >> -0x00000000000000001,
>> >> 0, -0x00000000000000001,
>> >> -0x00000000000000001>]()))->Eigen::DenseBase<Derived>::colwise [with
>> >> Derived
>> >> = Eigen::ArrayWrapper<Eigen::Matrix<float, -0x00000000000000001,
>> >> -0x00000000000000001, 0, -0x00000000000000001, -0x00000000000000001>
>> >> >]() *
>> >> ((Eigen::MatrixBase<Eigen::Matrix<float, -0x00000000000000001, 1, 0,
>> >> -0x00000000000000001, 1> >*)(& b))->Eigen::MatrixBase<Derived>::array
>> >> [with
>> >> Derived = Eigen::Matrix<float, -0x00000000000000001, 1, 0,
>> >> -0x00000000000000001, 1>]()’
>> >> ./Eigen/src/Core/../plugins/CommonCwiseUnaryOps.h:95: note: candidates
>> >> are:
>> >> const Eigen::CwiseUnaryOp<Eigen::ei_scalar_multiple2_op<float,
>> >> std::complex<float> >, Eigen::ArrayWrapper<Eigen::Matrix<float,
>> >> -0x00000000000000001, 1, 0, -0x00000000000000001, 1> > >
>> >> Eigen::operator*(const std::complex<float>&, const
>> >> Eigen::ArrayBase<Eigen::ArrayWrapper<Eigen::Matrix<float,
>> >> -0x00000000000000001, 1, 0, -0x00000000000000001, 1> > >&)
>> >> ./Eigen/src/Core/../plugins/CommonCwiseUnaryOps.h:91: note:
>> >> const Eigen::CwiseUnaryOp<Eigen::ei_scalar_multiple_op<float>,
>> >> Eigen::ArrayWrapper<Eigen::Matrix<float, -0x00000000000000001, 1, 0,
>> >> -0x00000000000000001, 1> > > Eigen::operator*(const float&, const
>> >> Eigen::ArrayBase<Eigen::ArrayWrapper<Eigen::Matrix<float,
>> >> -0x00000000000000001, 1, 0, -0x00000000000000001, 1> > >&)
>> >> ./Eigen/src/Core/../plugins/CommonCwiseUnaryOps.h:95: note:
>> >> const Eigen::CwiseUnaryOp<Eigen::ei_scalar_multiple2_op<float,
>> >> std::complex<float> >, Eigen::ArrayWrapper<Eigen::Matrix<float,
>> >> -0x00000000000000001, -0x00000000000000001, 0, -0x00000000000000001,
>> >> -0x00000000000000001> > > Eigen::operator*(const std::complex<float>&,
>> >> const
>> >> Eigen::ArrayBase<Eigen::ArrayWrapper<Eigen::Matrix<float,
>> >> -0x00000000000000001, -0x00000000000000001, 0, -0x00000000000000001,
>> >> -0x00000000000000001> > >&)
>> >> ./Eigen/src/Core/../plugins/CommonCwiseUnaryOps.h:91: note:
>> >> const Eigen::CwiseUnaryOp<Eigen::ei_scalar_multiple_op<float>,
>> >> Eigen::ArrayWrapper<Eigen::Matrix<float, -0x00000000000000001,
>> >> -0x00000000000000001, 0, -0x00000000000000001, -0x00000000000000001> >
>> >> >
>> >> Eigen::operator*(const float&, const
>> >> Eigen::ArrayBase<Eigen::ArrayWrapper<Eigen::Matrix<float,
>> >> -0x00000000000000001, -0x00000000000000001, 0, -0x00000000000000001,
>> >> -0x00000000000000001> > >&)
>> >> ./Eigen/src/Core/../plugins/CommonCwiseUnaryOps.h:95: note:
>> >> const Eigen::CwiseUnaryOp<Eigen::ei_scalar_multiple2_op<float,
>> >> std::complex<float> >, Eigen::Matrix<float, -0x00000000000000001,
>> >> -0x00000000000000001, 0, -0x00000000000000001, -0x00000000000000001> >
>> >> Eigen::operator*(const std::complex<float>&, const
>> >> Eigen::MatrixBase<Eigen::Matrix<float, -0x00000000000000001,
>> >> -0x00000000000000001, 0, -0x00000000000000001, -0x00000000000000001>
>> >> >&)
>> >> ./Eigen/src/Core/../plugins/CommonCwiseUnaryOps.h:91: note:
>> >> const Eigen::CwiseUnaryOp<Eigen::ei_scalar_multiple_op<float>,
>> >> Eigen::Matrix<float, -0x00000000000000001, -0x00000000000000001, 0,
>> >> -0x00000000000000001, -0x00000000000000001> > Eigen::operator*(const
>> >> float&,
>> >> const Eigen::MatrixBase<Eigen::Matrix<float, -0x00000000000000001,
>> >> -0x00000000000000001, 0, -0x00000000000000001, -0x00000000000000001>
>> >> >&)
>> >> ./Eigen/src/Core/../plugins/CommonCwiseUnaryOps.h:95: note:
>> >> const Eigen::CwiseUnaryOp<Eigen::ei_scalar_multiple2_op<float,
>> >> std::complex<float> >, Eigen::Matrix<float, -0x00000000000000001, 1, 0,
>> >> -0x00000000000000001, 1> > Eigen::operator*(const std::complex<float>&,
>> >> const Eigen::MatrixBase<Eigen::Matrix<float, -0x00000000000000001, 1,
>> >> 0,
>> >> -0x00000000000000001, 1> >&)
>> >> ./Eigen/src/Core/../plugins/CommonCwiseUnaryOps.h:91: note:
>> >> const Eigen::CwiseUnaryOp<Eigen::ei_scalar_multiple_op<float>,
>> >> Eigen::Matrix<float, -0x00000000000000001, 1, 0, -0x00000000000000001,
>> >> 1> >
>> >> Eigen::operator*(const float&, const
>> >> Eigen::MatrixBase<Eigen::Matrix<float,
>> >> -0x00000000000000001, 1, 0, -0x00000000000000001, 1> >&)
>> >> [2]+  Done                    gedit test.cpp
>> >> cjb@cjb-laptop:/tmp/eigen\$ g++ test.cpp -I.
>> >> test.cpp: In function ‘int main()’:
>> >> test.cpp:20: error: no match for ‘operator*’ in
>> >> ‘((Eigen::DenseBase<Eigen::ArrayWrapper<Eigen::Matrix<float,
>> >> -0x00000000000000001, -0x00000000000000001, 0, -0x00000000000000001,
>> >> -0x00000000000000001> > >*)(&((Eigen::MatrixBase<Eigen::Matrix<float,
>> >> -0x00000000000000001, -0x00000000000000001, 0, -0x00000000000000001,
>> >> -0x00000000000000001> >*)(& a))->Eigen::MatrixBase<Derived>::array
>> >> [with
>> >> Derived = Eigen::Matrix<float, -0x00000000000000001,
>> >> -0x00000000000000001,
>> >> 0, -0x00000000000000001,
>> >> -0x00000000000000001>]()))->Eigen::DenseBase<Derived>::colwise [with
>> >> Derived
>> >> = Eigen::ArrayWrapper<Eigen::Matrix<float, -0x00000000000000001,
>> >> -0x00000000000000001, 0, -0x00000000000000001, -0x00000000000000001>
>> >> >]() *
>> >> ((Eigen::MatrixBase<Eigen::Matrix<float, -0x00000000000000001, 1, 0,
>> >> -0x00000000000000001, 1> >*)(& b))->Eigen::MatrixBase<Derived>::array
>> >> [with
>> >> Derived = Eigen::Matrix<float, -0x00000000000000001, 1, 0,
>> >> -0x00000000000000001, 1>]()’
>> >> ./Eigen/src/Core/../plugins/CommonCwiseUnaryOps.h:95: note: candidates
>> >> are:
>> >> const Eigen::CwiseUnaryOp<Eigen::ei_scalar_multiple2_op<float,
>> >> std::complex<float> >, Eigen::ArrayWrapper<Eigen::Matrix<float,
>> >> -0x00000000000000001, 1, 0, -0x00000000000000001, 1> > >
>> >> Eigen::operator*(const std::complex<float>&, const
>> >> Eigen::ArrayBase<Eigen::ArrayWrapper<Eigen::Matrix<float,
>> >> -0x00000000000000001, 1, 0, -0x00000000000000001, 1> > >&)
>> >> ./Eigen/src/Core/../plugins/CommonCwiseUnaryOps.h:91: note:
>> >> const Eigen::CwiseUnaryOp<Eigen::ei_scalar_multiple_op<float>,
>> >> Eigen::ArrayWrapper<Eigen::Matrix<float, -0x00000000000000001, 1, 0,
>> >> -0x00000000000000001, 1> > > Eigen::operator*(const float&, const
>> >> Eigen::ArrayBase<Eigen::ArrayWrapper<Eigen::Matrix<float,
>> >> -0x00000000000000001, 1, 0, -0x00000000000000001, 1> > >&)
>> >> ./Eigen/src/Core/../plugins/CommonCwiseUnaryOps.h:95: note:
>> >> const Eigen::CwiseUnaryOp<Eigen::ei_scalar_multiple2_op<float,
>> >> std::complex<float> >, Eigen::ArrayWrapper<Eigen::Matrix<float,
>> >> -0x00000000000000001, -0x00000000000000001, 0, -0x00000000000000001,
>> >> -0x00000000000000001> > > Eigen::operator*(const std::complex<float>&,
>> >> const
>> >> Eigen::ArrayBase<Eigen::ArrayWrapper<Eigen::Matrix<float,
>> >> -0x00000000000000001, -0x00000000000000001, 0, -0x00000000000000001,
>> >> -0x00000000000000001> > >&)
>> >> ./Eigen/src/Core/../plugins/CommonCwiseUnaryOps.h:91: note:
>> >> const Eigen::CwiseUnaryOp<Eigen::ei_scalar_multiple_op<float>,
>> >> Eigen::ArrayWrapper<Eigen::Matrix<float, -0x00000000000000001,
>> >> -0x00000000000000001, 0, -0x00000000000000001, -0x00000000000000001> >
>> >> >
>> >> Eigen::operator*(const float&, const
>> >> Eigen::ArrayBase<Eigen::ArrayWrapper<Eigen::Matrix<float,
>> >> -0x00000000000000001, -0x00000000000000001, 0, -0x00000000000000001,
>> >> -0x00000000000000001> > >&)
>> >> ./Eigen/src/Core/../plugins/CommonCwiseUnaryOps.h:95: note:
>> >> const Eigen::CwiseUnaryOp<Eigen::ei_scalar_multiple2_op<float,
>> >> std::complex<float> >, Eigen::Matrix<float, -0x00000000000000001,
>> >> -0x00000000000000001, 0, -0x00000000000000001, -0x00000000000000001> >
>> >> Eigen::operator*(const std::complex<float>&, const
>> >> Eigen::MatrixBase<Eigen::Matrix<float, -0x00000000000000001,
>> >> -0x00000000000000001, 0, -0x00000000000000001, -0x00000000000000001>
>> >> >&)
>> >> ./Eigen/src/Core/../plugins/CommonCwiseUnaryOps.h:91: note:
>> >> const Eigen::CwiseUnaryOp<Eigen::ei_scalar_multiple_op<float>,
>> >> Eigen::Matrix<float, -0x00000000000000001, -0x00000000000000001, 0,
>> >> -0x00000000000000001, -0x00000000000000001> > Eigen::operator*(const
>> >> float&,
>> >> const Eigen::MatrixBase<Eigen::Matrix<float, -0x00000000000000001,
>> >> -0x00000000000000001, 0, -0x00000000000000001, -0x00000000000000001>
>> >> >&)
>> >> ./Eigen/src/Core/../plugins/CommonCwiseUnaryOps.h:95: note:
>> >> const Eigen::CwiseUnaryOp<Eigen::ei_scalar_multiple2_op<float,
>> >> std::complex<float> >, Eigen::Matrix<float, -0x00000000000000001, 1, 0,
>> >> -0x00000000000000001, 1> > Eigen::operator*(const std::complex<float>&,
>> >> const Eigen::MatrixBase<Eigen::Matrix<float, -0x00000000000000001, 1,
>> >> 0,
>> >> -0x00000000000000001, 1> >&)
>> >> ./Eigen/src/Core/../plugins/CommonCwiseUnaryOps.h:91: note:
>> >> const Eigen::CwiseUnaryOp<Eigen::ei_scalar_multiple_op<float>,
>> >> Eigen::Matrix<float, -0x00000000000000001, 1, 0, -0x00000000000000001,
>> >> 1> >
>> >> Eigen::operator*(const float&, const
>> >> Eigen::MatrixBase<Eigen::Matrix<float,
>> >> -0x00000000000000001, 1, 0, -0x00000000000000001, 1> >&)
>> >>
>> >>
>> >> On Wed, Sep 29, 2010 at 7:49 PM, Benoit Jacob
>> >> <jacob.benoit.1@xxxxxxxxx>
>> >> wrote:
>> >>>
>> >>> Does a.array().colwise() * b.array() work ?
>> >>>
>> >>> We're a bit pedantic if we require putting array() here since the
>> >>> colwise() makes it clear what you want to do...
>> >>>
>> >>> Benoit
>> >>>
>> >>> 2010/9/29 Carlos Becker <carlosbecker@xxxxxxxxx>:
>> >>> > Hi Benoit. No, it doesn't work and it makes sense, since it would be
>> >>> > like
>> >>> > multiplying a vector by a vector algebraically, which has no sense
>> >>> > for a
>> >>> > Matrix type (has it?)
>> >>> > I wanted to do element-wise multiplication, and I thought that
>> >>> > .array().colwise() would cope with that. Just to clarify, I want to
>> >>> > do:
>> >>> > if A = [1 2;
>> >>> >           3 4]
>> >>> > and B = [a;b] (matlab notation)
>> >>> > then I want to get something like:
>> >>> > result = [ 1*a, 2*a;
>> >>> >              3*b 4*b ]
>> >>> > Should I do this another way? I thought that .array().colwise() was
>> >>> > defined
>> >>> > to apply the element-wise operation for every column vector in A.
>> >>> > Thanks
>> >>> >
>> >>> > On Wed, Sep 29, 2010 at 7:41 PM, Benoit Jacob
>> >>> > <jacob.benoit.1@xxxxxxxxx>
>> >>> > wrote:
>> >>> >>
>> >>> >> 2010/9/29 Carlos Becker <carlosbecker@xxxxxxxxx>:
>> >>> >> > Hi all, I was trying to code something like this:
>> >>> >> > #include <Eigen/Dense>
>> >>> >> > using namespace Eigen;
>> >>> >> > using namespace std;
>> >>> >> > int main()
>> >>> >> > {
>> >>> >> > MatrixXf a;
>> >>> >> > VectorXf b;
>> >>> >> > a.resize(2,4);
>> >>> >> > b.resize(2);
>> >>> >> > a << 1,2,
>> >>> >> > 3,4,
>> >>> >> > 5,6,
>> >>> >> > 7,8;
>> >>> >> > b << 1,2;
>> >>> >> > a = a.array().colwise() * b;
>> >>> >>
>> >>> >> Here you're multiplying an array by a matrix.
>> >>> >>
>> >>> >> Doesn't a.colwise() * b work?
>> >>> >>
>> >>> >> Benoit
>> >>> >>
>> >>> >> > return 0;
>> >>> >> > }
>> >>> >> > Should this compile correctly? I want to multiply every column in
>> >>> >> > matrix
>> >>> >> > a,
>> >>> >> > element-wise, with vector b, but I cannot make it work
>> >>> >> > I hope I am not forgetting about something important here.
>> >>> >> > Cheers,
>> >>> >> > Carlos
>> >>> >>
>> >>> >>
>> >>> >
>> >>> >
>> >>>
>> >>>
>> >>
>> >>
>> >
>>
>>
>
>

```

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