Re: [eigen] eigen sqrt compilation error

[Gael Guennebaud <gael.guennebaud@xxxxxxxxx>]

I'm ok with that big Eigen header.

btw, using such a big header with precompiled header generates a 28MB
binary, and it speeds up the compilation of your example by a factor
2:

everytime a file in eigen change:
g++ -O2 -DNDEBUG -x c++-header path_to_eigen2/Eigen/Eigen


g++ -O2 -DNDEBUG example.cpp -I. -Ipath_to_eigen2/

where example.cpp starts with:
#include <Eigen/Eigen>

gael

On Fri, Jun 19, 2009 at 2:53 PM, Benoit Jacob<jacob.benoit.1@xxxxxxxxx> 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
>
>
>