On Sun, Jun 12, 2011 at 1:33 PM, Mohammad Mirzadeh <mirzadeh at gmail.com>wrote:
> Thanks Barry. Problem is my indices are all long and if I use the with > petsc the compiler will complain. Do you think casting them to int will > solve the problem? Also how does 64 bit international affect petsc > performance? > The words here are too imprecise: short int: A 2 byte integer long int: A 4 byte integer int: An integer which can be short or long, depending on the compiler, but most often long int today long long int: An 8 byte integer The --with-64-bit-indices flag gives long long ints. If you have > 2B unknowns, use this, otherwise don't. Yes, it slows things down. On every 64-bit architecture I know, 'int' is still 'long int', not 'long long int'. The only thing that is 64-bit is the pointers. Matt > Thanks > On Jun 12, 2011 9:39 AM, "Barry Smith" <bsmith at mcs.anl.gov> wrote: > > > > On Jun 12, 2011, at 1:48 AM, Mohammad Mirzadeh wrote: > > > >> I guess I figured it out. On 64-bit OS long long and long are the same > and I may as well just use --with-64-bit-ints flag. > > > > You only need to configure PETSc with --with-64-bit-indices if you are > dealing with problems with over 2 billion unknowns (in parallel) or if the > sparse matrix will have more than 2 billion nonzeros on a single process. > You do not need to use --with-64-bit-indices just because you are using 64 > bit pointers, only for really large problems. > > > > > > Barry > > > >> > >> Thanks > >> > >> > >> On Sat, Jun 11, 2011 at 11:22 PM, Mohammad Mirzadeh <mirzadeh at gmail.com> > wrote: > >> Hi guys, > >> > >> How can I use long int instead of PetscInt in the functions? Does simply > changing the definition of PetscInt solve the problem? > >> > >> Thanks > >> > > > -- What most experimenters take for granted before they begin their experiments is infinitely more interesting than any results to which their experiments lead. -- Norbert Wiener -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20110612/65d09422/attachment.htm>
