Re: [petsc-users] Using DMDA with regular matrices
Great, thanks so much for the explanations! 获取 Outlook for Android<https://aka.ms/ghei36> From: Jed Brown Sent: Monday, March 16, 2020 9:22:16 PM To: Yuyun Yang ; petsc-users@mcs.anl.gov Subject: Re: [petsc-users] Using DMDA with regular matrices Yuyun Yang writes: > Hello team, > > Hope you're staying healthy amid the coronavirus craziness. > > Just want to ask a basic question: if my grid is managed by DMDA, then > do matrices in all my intermediate steps have to be compatible with > DMDA and formed in a special way, or can I just form them as usual > (i.e. do MatCreate, MatMPIAIJSetPreallocation, MatSetValue etc.)? DMCreateMatrix does the creation and preallocation for you, and enables you to use MatSetValuesStencil. It's otherwise the same. Sometimes people use auxiliary DMs to describe distribution of values that aren't the same size/shape as solution variables (e.g., cell-centered tensor-valued coefficients), though usually those are accessed in your residual and Jacobian assembly functions, not via matrices. > Asking this because I'm using a mix of matrix-free and matrix-based > operations, and MatShell seems to require the use of DMDA. MatShell has no dependence on DMDA. It's entirely in your hands, via the callback(s) that you implement.
Re: [petsc-users] Using DMDA with regular matrices
Yuyun Yang writes: > Hello team, > > Hope you're staying healthy amid the coronavirus craziness. > > Just want to ask a basic question: if my grid is managed by DMDA, then > do matrices in all my intermediate steps have to be compatible with > DMDA and formed in a special way, or can I just form them as usual > (i.e. do MatCreate, MatMPIAIJSetPreallocation, MatSetValue etc.)? DMCreateMatrix does the creation and preallocation for you, and enables you to use MatSetValuesStencil. It's otherwise the same. Sometimes people use auxiliary DMs to describe distribution of values that aren't the same size/shape as solution variables (e.g., cell-centered tensor-valued coefficients), though usually those are accessed in your residual and Jacobian assembly functions, not via matrices. > Asking this because I'm using a mix of matrix-free and matrix-based > operations, and MatShell seems to require the use of DMDA. MatShell has no dependence on DMDA. It's entirely in your hands, via the callback(s) that you implement.
[petsc-users] Using DMDA with regular matrices
Hello team, Hope you're staying healthy amid the coronavirus craziness. Just want to ask a basic question: if my grid is managed by DMDA, then do matrices in all my intermediate steps have to be compatible with DMDA and formed in a special way, or can I just form them as usual (i.e. do MatCreate, MatMPIAIJSetPreallocation, MatSetValue etc.)? Asking this because I'm using a mix of matrix-free and matrix-based operations, and MatShell seems to require the use of DMDA. Thanks for your help. Best, Yuyun
