[petsc-users] MatSetNearNullSpace() or PCSetCoordinate for GAMG ?

A.L. Siahaan als88 at cam.ac.uk
Thu Nov 8 14:54:37 CST 2012

Referring to the following thread about setting nullspace and coordinate 
for GAMG : 

Is there any difference of memory requirement (to set nullspace) between 
MatSetNearNullSpace() and PCSetCoordinate ?

For PCSetCoordinate, is the order of x-y-z coordinate in thevector [0.x, 
0.y, 0.z, 1.x, ..., N-1.z] with respect to the ordering of solution vector 
[0.u_x, 0.u_y, 0.u_z, 1.u_z, ..., N-1.u_z] ?

I tried to use PCSetCoordinate for GAMG, but then I get an error :
[0]PETSC ERROR: Floating point exception!
[0]PETSC ERROR: Infinite or not-a-number generated in mdot, entry 0!

I am wondering if it is due to the ordering of coordinate.


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