tolerance for diagonal entries + Slepc

Umut Tabak u.tabak at
Mon Aug 3 09:38:16 CDT 2009

Hong Zhang wrote:
> Umut,
> The error msg
> "Matrix is missing diagonal entry 1847!"
> has nothing to do with the tolerance.
> It indicates that you did not input any value
> to the 1847-th diagonal entry.
> Many routines required diagonal entries been
> allocated and set.
> If that entry is zero, you should set zero value to it.
> Hong
Hi Hong,

Thanks for the quick reply, that last part of the matrix in matrix 
market format, I read this with one of the examples that you can read in 
the matrix market real format:
1848 925 1.207005667e-06
1848 1032 1.545494254e-08
1848 1771 1.207005667e-06
1848 1777 4.828022669e-06
1848 1782 -3.078839811e-08
1848 1842 1.545494254e-08
1848 1848 6.181977018e-08 // this is source of the issue
So actually very close to zero. I have this numerical problem on most of 
my matrices that I would like to interface with Petsc. The point which 
made me think this way is that Matlab which uses Arpack to solve 
eigenvalue problems did not experience any problems to solve the system. 
In Petsc+Slepc, I ran into this problem(a generalized eigenvalue 

Best regards,

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