Re: Direct product of matrices.

Hi Art,

Your expression is highly dependent on the order of execution:

TMatrixD B(n,n);
B=A*A.T();

A.T() is transposing A in place , if the compiler performs that before the product,
the dimensions of the matrices are incompatible . You can accomplish the
operation as follows :

• TMatrixD B(A,TMatrixD::kMultTranspose,A);
• TMatrixD At(TMatrixD::kTransposed,A); TMatrixD B = A*At;
• TMatrixD At(1,5); At.Transpose(A); TMatrixD B = A*At;

where the first method creates the least temporary objects .

Eddy

• "Arthur E. Snyder" <snyder_at_slac.stanford.edu> wrote:

> Hi Rene et al.,
>
>
> Direct product of matrices which worked with HepMatrix does seem to
> work
> for TMatrix.
>
> That is if I do
>
> TMatrixD A(n,1);
> then set a to some falues
>
> TMatrixD B(n,n);
> B=A*A.T()
>
> it fails. Error message if about rows and columns not matching.
>
> This worked with HepMatrix and is useful, for example, in
> constructing
> array of derivatives that enters some fits.
>
> Is this a bug or a feature? Or am I doing something wrong?
>
> It not hard to write my own direct product function but it looks
> ugly...
>
> -Art S.
>
>
>
> A.E. Snyder, Group EC \!c*p?/
> SLAC Mail Stop #95 ((. .))
> Box 4349 |
> Stanford, Ca, USA, 94309 '\|/`
> e-mail:snyder_at_slac.stanford.edu o
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>
>
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>
Received on Wed Jan 31 2007 - 03:25:17 CET