Re: [petsc-users] Time integrated adjoints
Barry, Is the method exact if I have a time dependent mass matrix (dF/dU_t changes each time step)? I'm not sure it's possible if TSSetIJacobian expects a function which computes the combination of dF/dU and a*dF/dU_t. But, perhaps there is something I'm missing. Otherwise, it looks very comprehensive. I like how you added the cost integrand. If I recall correctly, the Trilinos package Rythmos is missing this. Thanks! Dave On Tue, Apr 14, 2015 at 8:30 AM, Barry Smith bsm...@mcs.anl.gov wrote: On Apr 14, 2015, at 1:06 AM, Dave Makhija makhi...@colorado.edu wrote: Hello, I'm evaluating my options for computing time dependent adjoints. I did not think PETSc supported this, but I see TSAdjointSolve in the development branch. That would be fantastic news if you plan to support time integrated adjoints! What features are envisioned and when is the targeted release date? Dave, We currently have discrete adjoint computations for explicit RK methods and for implicit theta methods (backward Euler and Crank-Nicholson). The development copy of the users manual has some discussion ( http://www.mcs.anl.gov/petsc/petsc-master/docs/manual.pdf page 135) and there are several examples. I urge you to try them out now in master and stay in contact with us to insure we provide what you need as we are actively developing them. We plan a release for early June. Barry Thanks! Dave
[petsc-users] Time integrated adjoints
Hello, I'm evaluating my options for computing time dependent adjoints. I did not think PETSc supported this, but I see TSAdjointSolve in the development branch. That would be fantastic news if you plan to support time integrated adjoints! What features are envisioned and when is the targeted release date? Thanks! Dave
[petsc-users] nnz's in finite element stiffness matrix
I used to have a decent setup that worked as follows: 1. Build node-element table (For a given node, which elements contain this node. You may already have this) OR build a node connectivity table (For a given node, which nodes are connected). 2. Build element-node table (For a given element, which nodes are contained in this element. You probably already have this) 4. Loop over nodes and get the global DOFs contained in that node. For those DOF id rows, add the number of nodal DOFs for each unique node connected to the current node using the node-element and element-node table OR the node connectivity table. 5. Loop over elements and add the number of elemental DOFs to each nodal DOF global id row contained in this element using element-node table. Also add the number of elemental DOF's and the sum of the nodal DOF's to the elemental global DOF id rows. 6. Add contributions of multi-point constraints, i.e. Lagrange multiplier DOF's. Note that in parallel you may have to scatter values to global DOF ids owned by off-processors to get an accurate Onz. This setup as a whole can be pretty fast but can scale poorly if you don't have a good way of developing the node-element table or node connectivity since it requires some loops within loops. Another way is to use the PETSc preallocation macros such as MatPreallocateSet. You can essentially do a dry run of a Jacobian Matrix assembly into the preallocation macros. They can be tricky to use, so if you have problems you can simply look at the PETSc documentation for those macros and hand code them yourself. This strategy will overestimate the memory, but a matrix inversion will dwarf how much this will waste. I vaguely remember a PETSc archive asking how to free the unneeded memory if this is absolutely necessary, but I don't think anything really worked without a full matrix copy. If someone by chance knows how the Trilinos OptimizeStorage routine works for Epetra matricies they could potentially shed some light on how to do this - if it is even possible. Dave Makhija On Tue, Sep 7, 2010 at 2:24 PM, stali stali at purdue.edu wrote: Petsc-users How can I efficiently calculate the _exact_ number of non-zeros that would be in the global sparse (stiffness) matrix given an unstructured mesh? Thanks
