Re: [petsc-users] VecNorm() of VECNEST returns 0 while sub-vectors have nonzero norms

Could you please share a runnable piece of code? I’ve tried to generate an example myself, and I don’t get 0 for the norm of G. Thanks, Pierre

On 6 Jan 2026, at 11:12 AM, Michael Wick <[email protected]> wrote:

Hello PETSc users,

I have a VECNEST norm issue and would appreciate help.

I create a nest vector: VecCreateNest(PETSC_COMM_WORLD, 2, NULL, subG, &G);

But: VecNorm(G, NORM_2, &nG) returns 0

While the sub-vectors are clearly nonzero: VecNestGetSubVec(G,0,&v0); VecNorm(v0,NORM_2,&n0); // n0 > 0 VecNestGetSubVec(G,1,&v1); VecNorm(v1,NORM_2,&n1); // n1 > 0

Can someone give a hint on what might go wrong?

Thanks,

M