Re: [eigen] eigen sqrt compilation error

[Mark Borgerding <mark@xxxxxxxxxxxxxx>]

I like this. 

* easy to get everything from Eigen you could possibly want with one include
* possible to go through the trouble of minimizing compile time or 
source file dependencies.
It seems like a good philosophy.

Guido Von Rossum is fond of saying "Make the easy things easy. Make the 
hard things possible." 

-- Mark


Benoit Jacob wrote:
> oh and there is another "nuclear option":
>
> add a convenience #include<Eigen/Eigen> that includes them all. And
> then keep the separate headers for the users who want every % of
> compilation speed.
>
> The idea is that Core and Array are the 2 biggest modules, so
> Eigen/Eigen won't be much slower than including them two.
>
> Benoit
>
> 2009/6/19 Benoit Jacob <jacob.benoit.1@xxxxxxxxx>
>   
> > 2009/6/19 Gael Guennebaud <gael.guennebaud@xxxxxxxxx>
> >     
> > > On Fri, Jun 19, 2009 at 12:29 PM, Patrick Mihelich
> > > <patrick.mihelich@xxxxxxxxx> wrote:
> > >       
> > > > On Fri, Jun 19, 2009 at 12:37 AM, Moritz Lenz <mlenz@xxxxxxxxxxxxxxxxxxxxxxx> wrote:
> > > >         
> > > > > Considering the number of times people make this error (forgetting to include it), what about including it by default? Is there a very good reason not to do it?
> > > > >           
> > > > I wonder this too. I ran into this error when I started using Eigen, and it seems to pop up regularly on the list. What exactly is the cost of including <Eigen/Array> in the core? How much does it increase compile times?
> > > >         
> > > on my high end computer with gcc 4.3.2 -O2 -DNDEBUG, much less time
> > > than to compile: Vector3f a, b; cout << a+b;, so something around 0.02
> > > sec.
> > >       
> > On my computer I tried this program:
> >
> > #include <Eigen/Core>
> > //#include <Eigen/Array>
> >
> > using namespace Eigen;
> >
> > int main() {
> >  Matrix3d m = Matrix3d::Identity();
> >  Matrix3d n = m+m;
> >  Vector3d v; v << 1, 2, 3;
> >  Vector3d w = v+v;
> >  w = m * w;
> >  std::cout << w << std::endl;
> > }
> >
> > with g++ 4.3.3. I repeated the compilation 10 times.
> >
> > The #include<Eigen/Array> increases compilation times by 2.5% and the
> > memory usage is not affected.
> >
> > I'm OK to consider this reasonable, especially as other modules like
> > Geometry already include Array.
> > What's your opinion?
> >
> > The next question would be: should we merge the Array/ files into
> > Core/ or just #include<Array> in Core.
> >
> > Benoit
> >     
>
>
>