On Mar 15, 2011, at 6:25 PM, Jed Brown wrote: > On Wed, Mar 16, 2011 at 00:13, Barry Smith <bsmith at mcs.anl.gov> wrote: > You cannot just check the row and column separately. You need to check them > as a pair. If row < m and column < n mark A as changed. > > But you don't know what "A" is yet so all you can mark is some particular > pair (row,col) as changed.
Of course I know what A is. Because I am only doing this tracking after a MatGetSubmatrix() has been called which provide the information about what A is. Barry > And you can't store cheaply in the form (row_range, col_range) because you > don't know when to extend an existing range or when to create a new range. > Maybe there is something clever that works in a lot of common cases, but I > don't think there is a cheap automatic way to do this. I think you would have > to declare index sets for submatrices up-front.
