Matrix properties
number of rows	240,000
number of columns	120,000
nonzeros	711,683
structural full rank?	yes
structural rank	120,000
# of blocks from dmperm	1
# strongly connected comp.	7,516
explicit zero entries	0
nonzero pattern symmetry	0%
numeric value symmetry	0%
type	real
structure	rectangular
Cholesky candidate?	no
positive definite?	no

author	Y Yoshiyasu
editor	T. Davis
date	2009
kind	computer graphics/vision problem
2D/3D problem?	yes

Additional fields	size and type
b	full 240000-by-2

Notes:

The problem is template-mesh deformation to match with silhouettes.  In this 
process, there are two kinds of linear systems to solve.  This system        
(Yoshiyasu/image_interp) is a smooth vector field construction from images,  
which is harmonic interpolation (minimizing laplacian: Lx=0) of intensity    
gradient field p.  This can be solved by normal equation and cholesky        
factorization, x=(A1'*A1)/(A1'*b1), where A1=[L;C] and                       
b1=[zeros(size(length(L),1);1);C*p]. C is a square diagonal matrix containing
weights.  This is for a 400x300 image, so Ix=reshape(x,400,300) must be done 
to get the vector field. After solving y direction for Iy, the result is     
visualized with quiver(Ix,Iy).   At each iteration the both C submatrix and  
the right-hand-side change but L remains unchanged.  [Note by T. Davis:      
since C is of high rank, update/downdate will not be effective, since it is  
meant for low-rank changes.]                                                 

Ordering statistics:	result
nnz(V) for QR, upper bound nnz(L) for LU, with COLAMD	316,991,703
nnz(R) for QR, upper bound nnz(U) for LU, with COLAMD	12,952,004

For a description of the statistics displayed above, click here.

Maintained by Tim Davis, last updated 12-Mar-2014.
Matrix pictures by cspy, a MATLAB function in the CSparse package.
Matrix graphs by Yifan Hu, AT&T Labs Visualization Group.