Re: [eigen] Documentation : it's a sprint!!

[Carlos Becker <carlosbecker@xxxxxxxxx>]

I thought that with matrix.colwise().sum(), colwise() is treated as a visitor, and with += it is a broadcasting operation. This is because I read this on your tutorial proposal:

7. Reductions, visitors, and broadcasting
 - for all kinds of matrices/arrays
 - sum() etc...
 - mention partial reductions with .colwise()...
 - mention broadcasting e.g. m.colwise() += vector;

I thought that partial reductions were done with visitors and broadcasting was something similar but with 'write access'. Or maybe both are visitors, I guess I am missing many concepts here.

On Thu, Jul 1, 2010 at 2:46 PM, Benoit Jacob <jacob.benoit.1@xxxxxxxxx> wrote:

Broadcasting means e.g.

    matrix.colwise() += vector;

Visitors are e.g.

   Index i, j;
   matrix.maxCoeff(&i, &j);

These are two really different things, no?
Benoit

2010/7/1 Carlos Becker <carlosbecker@xxxxxxxxx>:

> Just a quick question: what would be the difference between visitors and
> broadcasting? Seems to me that broadcasting is able to 'visit' column or
> row-wise, also modifying the data inside the matrix/array object, am I
> right? I haven't used broadcasting with eigen before.
>
>
>
> On Wed, Jun 30, 2010 at 1:30 PM, Carlos Becker <carlosbecker@xxxxxxxxx>
> wrote:
>>
>> oh ok sorry, got confused since I thought that someone was alreay writing
>> the sparse tut
>>
>>
>> On Wed, Jun 30, 2010 at 1:29 PM, Gael Guennebaud
>> <gael.guennebaud@xxxxxxxxx> wrote:
>>>
>>> nevermind, this C07_TutorialSparse.dox file is an old one...
>>>
>>> gael
>>>
>>> On Wed, Jun 30, 2010 at 2:26 PM, Carlos Becker <carlosbecker@xxxxxxxxx>
>>> wrote:
>>> > I am starting with the reductions/visitors/broadcasting tutorial and
>>> > just
>>> > noticed that the sparse tutorial is named as C07_TutorialSparse.dox.
>>> > According to the order in http://eigen.tuxfamily.org/dox-devel/ it
>>> > should be
>>> > C08 and C07 is to be the one I am doing. This is a silly question but
>>> > just
>>> > wanted to make sure we are all following the same conventions.
>>> > Carlos
>>> >
>>> > On Sun, Jun 27, 2010 at 1:59 PM, Gael Guennebaud
>>> > <gael.guennebaud@xxxxxxxxx>
>>> > wrote:
>>> >>
>>> >> On Sun, Jun 27, 2010 at 12:41 PM, Carlos Becker
>>> >> <carlosbecker@xxxxxxxxx>
>>> >> wrote:
>>> >> > Mmm I am trying to think of a straightforward explanation for this.
>>> >> > What
>>> >> > do
>>> >> > you think about calling them fixed-size and dynamic-size blocks,
>>> >> > where
>>> >> > the
>>> >> > former differs from the later because its size is known at
>>> >> > compile-time.
>>> >>
>>> >> a slightly more precise variant: "the latter are optimized versions of
>>> >> the former when the size is known at compile-time." I just added the
>>> >> word "optimized"
>>> >>
>>> >> you might also have a look at the reference tables, section "Sub
>>> >> matrices" to see how they are presented. The old version of this
>>> >> section is available online there:
>>> >>
>>> >>
>>> >>
>>> >> http://eigen.tuxfamily.org/dox-devel/TutorialCore.html#TutorialCoreMatrixBlocks
>>> >>
>>> >> gael
>>> >>
>>> >> >
>>> >> >
>>> >> > On Sun, Jun 27, 2010 at 11:02 AM, Carlos Becker
>>> >> > <carlosbecker@xxxxxxxxx>
>>> >> > wrote:
>>> >> >>
>>> >> >> Yes, I got that and actually it was my mistake since I supposed
>>> >> >> that it
>>> >> >> was only for fixed-size matrices, so now I am changing it.
>>> >> >> Thanks,
>>> >> >>
>>> >> >>
>>> >> >> 2010/6/27 Björn Piltz <bjornpiltz@xxxxxxxxxxxxxx>
>>> >> >>>
>>> >> >>> "The following tables show a summary of Eigen's block operations
>>> >> >>> and
>>> >> >>> how
>>> >> >>> they are applied to fixed- and dynamic-sized Eigen objects."
>>> >> >>> This quote and the following table gives the impression that  the
>>> >> >>> fixed
>>> >> >>> size functions are only available for fixed size matrices. But
>>> >> >>> using
>>> >> >>> fixed
>>> >> >>> size vs dynamic size functions acually only determin the return
>>> >> >>> type.
>>> >> >>> Björn
>>> >> >
>>> >> >
>>> >>
>>> >>
>>> >
>>> >
>>>
>>>
>>
>
>