On Thu, 1 Nov 2007, Zhifeng Sheng wrote:
> Dear all > > It is always not easy to determine the number of nonzeros in a row without > any cost. > > I wonder if I can make dynamic allocation, for instance, if one found the > nonzeros of a row overflow the pre-allocated space, then the space shall be > doubled. > > This may waste some memory but it may not be that bad. Or maybe this is > already done in Petsc? This is implemented in petsc, and is the reasons that MatAssembly may become extremely slow when user does not preallocate memory. > > Could please tell what happens if I assign the nozero number in rows to be > zeros and let the programme fills in the nonzeros ? It would be better that you assign a max nozero number than zero to reduce memory malloc. Hong > > Best regards > Zhifeng Sheng > >
