Matrix properties
number of rows	71,505
number of columns	71,505
nonzeros	5,294,285
structural full rank?	yes
structural rank	71,505
# of blocks from dmperm	1
# strongly connected comp.	1
entries not in dmperm blocks	0
explicit zero entries	0
nonzero pattern symmetry	symmetric
numeric value symmetry	symmetric
type	real
structure	symmetric
Cholesky candidate?	yes
positive definite?	no

author	P. Koutsovasilis
editor	T. Davis
date	2007
kind	structural problem
2D/3D problem?	yes

Notes:

Stiffness matrix from an AUDI engine piston rod.  This matrix is an ill-     
condition symmetric indefinite matrix.  In MATLAB 7.4, the matrix is         
factorized three times in x=A\b.  Inside backslash, CHOLMOD is tried first   
since the matrix is symmetric and all diagonal entries are positive.  CHOLMOD
fails since the matrix is indefinite.  Next, UMFPACK is used with default    
pivot tolerances which maintain sparsity at the (rare) expense of a slight   
decrease in accuracy.  This succeeds, but the result is flagged as           
potentially inaccurate because the condition estimate is high.  UMFPACK is   
then used again with more conservative tolerances (but more fill-in).        

Ordering statistics:	AMD	METIS
nnz(chol(P*(A+A'+s*I)*P'))	20,756,208	21,041,811
Cholesky flop count	1.2e+10	1.2e+10
nnz(L+U), no partial pivoting	41,440,911	42,012,117
nnz(V) for QR, upper bound nnz(L) for LU	40,210,857	40,468,056
nnz(R) for QR, upper bound nnz(U) for LU	109,796,898	107,281,795

Maintained by Tim Davis, last updated 04-May-2008.
Matrix pictures by cspy, a MATLAB function in the CSparse package.
Matrix graphs by Yifan Hu, AT&T Labs Visualization Group.