Re: [eigen] Transform.rotation() hang

["Schleimer, Ben" <bensch128@xxxxxxxxx>]

It seems to me to be more useful and powerful to have a general map(Functor) for a matrix then write special case coeff-wise methods. 
It make also make some of the uses of cwise more understandable.

template <typename T>
struct Truncator { 
  const T mVal;
  Truncator(const T& v) : mVal(v) {}
  T operator()(const T& in) const { return mVal<=in ? in: T(); }
}

Matrix4f m << some matrix...;
Truncator f(m.norm());
m = m.map<Truncator>(f);

It might be easier to do some of the cwise operations this way 
(like comparisons, "m.cwise() <= m2" seems odd)
Of course, I don't know if this would work for vectorization

just my $0.02
Ben




--- On Tue, 2/10/09, Keir Mierle <mierle@xxxxxxxxx> wrote:

> From: Keir Mierle <mierle@xxxxxxxxx>
> Subject: Re: [eigen] Transform.rotation() hang
> To: eigen@xxxxxxxxxxxxxxxxxxx
> Date: Tuesday, February 10, 2009, 5:03 PM
> I suspect a .truncate() function would be generally useful.
> 
> Matrix... M;
> M.truncate()
> M.clampSmallValues()
> M.truncateNegligible()
> M.?  Other ideas?
> 
> Keir
> 
> On Tue, Feb 10, 2009 at 1:01 PM, Benoit Jacob
> <jacob.benoit.1@xxxxxxxxx>wrote:
> 
> > Meanwhile, here are some thoughts if you absolutely
> have to live with
> > the current SVD.
> >
> > What I can see on your matrices, is that while their
> norm is (of the
> > order of magnitude of) 1, they have some coefficients
> of the order of
> > magnitude of 1e-300. That could easily be what
> triggers a bug in the
> > current SVD.
> >
> > So one thing you can do, before calling the SVD (i.e.
> before calling
> > rotation()) is to:
> > 1) compute N = matrix.norm()
> > 2) for each entry matrix(i,j),
> >  if(ei_isMuchSmallerThan(matrix(i,j), N))
> >    matrix(i,j) = 0;
> >
> > Cheers,
> > Benoit
> >
> > 2009/2/10 Ben Axelrod <baxelrod@xxxxxxxxxxxx>:
> > > Sometimes calling Eigen::Transform.rotation()
> hangs and does not return.
> > >
> > >
> > >
> > > This transform matrix runs fine:
> > >
> > > 1            0   -1.931e-312  1
> > >
> > > 0            1    0           0
> > >
> > > 1.931e-312   0    1           1.5
> > >
> > > 0            0    0           1
> > >
> > >
> > >
> > > This transform matrix hangs:
> > >
> > > 1            0   -2.357e-312  1
> > >
> > > 0            1    0           0
> > >
> > > 1.179e-311   0    5           7.5
> > >
> > > 0            0    0           1
> > >
> > >
> > >
> > >
> > >
> > > Any help?
> > >
> > >
> > >
> > > Detailed info: the transforms were computed by:
> > >
> > >
> > >
> > > Tf * Tr * Qt * Sc
> > >
> > >
> > >
> > > Where, for the good transform:
> > >
> > >
> > >
> > > Tf = Transform:
> > >
> > > 1 0 0 1
> > >
> > > 0 1 0 0
> > >
> > > 0 0 1 0
> > >
> > > 0 0 0 1
> > >
> > >
> > >
> > > Tr = Translation:
> > >
> > > 0
> > >
> > > 0
> > >
> > > 1.5
> > >
> > >
> > >
> > > Qt = Quaternion:
> > >
> > > 0
> > >
> > > -9.653e-313
> > >
> > > 0
> > >
> > > 1
> > >
> > >
> > >
> > > Sc = Scaling:
> > >
> > > 1
> > >
> > > 1
> > >
> > > 1
> > >
> > >
> > >
> > >
> > >
> > > And for the bad transform:
> > >
> > >
> > >
> > > Tf = Transform:
> > >
> > > 1 0 0 1
> > >
> > > 0 1 0 0
> > >
> > > 0 0 5 0
> > >
> > > 0 0 0 1
> > >
> > >
> > >
> > > Tr = Translation:
> > >
> > > 0
> > >
> > > 0
> > >
> > > 1.5
> > >
> > >
> > >
> > > Qt = Quaternion:
> > >
> > > 0
> > >
> > > -1.179e-312
> > >
> > > 0
> > >
> > > 1
> > >
> > >
> > >
> > > Sc = Scaling:
> > >
> > > 1
> > >
> > > 1
> > >
> > > 1
> > >
> > >
> > >
> > >
> > >
> > > Thanks,
> > >
> > > -Ben
> >
> >
> >