[petsc-dev] Unions of IS and MatNest

[Pierre Jolivet]

Hello,
Has there been any follow-up on this https://lists.mcs.anl.gov/pipermail/petsc-users/2015-January/024020.html <https://lists.mcs.anl.gov/pipermail/petsc-users/2015-January/024020.html>?
Given a 3x3 MatNest A = [A_00,0,0 ; 0,A_11,0 ; 0,0,A_22], I’d like to setup a two-way fieldsplit coupling [A_00,0 ; 0,A_11] and [A_22] but I can’t figure out the proper options.
Jed, in this answer https://lists.mcs.anl.gov/pipermail/petsc-users/2015-January/023993.html <https://lists.mcs.anl.gov/pipermail/petsc-users/2015-January/023993.html>, you recommend not to use MatNest. What would you recommend instead?
Even defining a 2x2 MatNest B = [B_00,0 ; 0,A_22] with B_00 = [A_00,0 ; 0,A_11] sounds bad to you?

Thanks for your help,
Pierre

PS: this is just a dummy example with 0s everywhere.

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