Questions tagged [petsc]
PETSc is an open source suite of data structures and routines for the scalable (parallel) solution of scientific applications modeled by partial differential equations.
15
questions with no upvoted or accepted answers
4
votes
0answers
238 views
Is it possible to predict the null space of a structure from contributing elements null spaces?
I am trying to solve an almost incompressible problem with heterogeneous properties by domain decomposition. Solution with CG converges slowly or divergerces completely. My problem becomes ill-...
3
votes
0answers
67 views
PETSc SNES for user defined state
How to use PETSc SNES (scalable nonlinear equation solver), when the solution is not a vector but a user defined state?
I am implementing a non-linear mechanics problem (geometrically exact shell 5-...
3
votes
0answers
235 views
Method with low memory requirement for large-scale eigenvalue problem
I am working on the flow stability problem. In this work the main complication is solving generalized eigenvalue problem for a large scale Non-Hermitian matrix. I need only one eigenvalue (most left ...
3
votes
0answers
156 views
Is there an easy way to read a PetscBag into a python dict?
I'm using a PetscBag to store the input parameters of my program. At some point, I'm going to need to use python to plot these parameters against some output parameters, and ...
2
votes
0answers
158 views
Is it worth switching to timesteppers provided by PETSc if I can't write down a Jacobian for my problem? Case study with “the amoeba” toy problem
I am considering using petsc4py instead of scipy.integrate.odeint (which is a wrapper for Fortran solvers) for a problem ...
2
votes
0answers
147 views
preconditioned Uzawa method with Petsc
I am trying to improve the resolution of a Stokes problem (P2/P1 on unstructured mesh) defined by the matrix $M$:
$M=
\begin{pmatrix}
A_u & 0 & B_u \\
0 & A_v & B_v\\
B_u^T & B_v^...
2
votes
0answers
536 views
Jacobian-Free Newton-Krylov vs explicitly forming jacobian in DG
For a given discontinuous galerkin (DG) implementation for Navier-Stokes, targeting 10,000 to 1,000,000 4th order cells in 3D, I'm using PETSc's suite of linear/non-linear solvers on the back-end. It ...
2
votes
0answers
585 views
Cusp Library performance worse than PETSC (GMRES 200 iterations) Why?
I wanted to compare the speeds of the GMRES implementations in the CUSP and the PETSc libraries.
The matrix (A) used for testing was a 3d Laplacian matrix obtained by using the 7 point stencil on a ...
1
vote
1answer
97 views
Solving nonlinear PDE with finite difference based on Newton-Krylov
I am now working on solving MHD equations with finite difference method, which include nonlinear equations:
$$
\frac{\partial\rho}{\partial t}+\nabla\cdot\left[\left(\rho_0+\rho\right){v}\right]-\...
1
vote
0answers
127 views
Getting started with FEM: Ill-conditioned matrix when evaluating flux terms in conservation law?
I have a system of conservation laws of the form
$$ \frac{\partial \mathbf{q}}{\partial t} + \nabla \cdot \mathbf{F}\!\left(\mathbf{q}\right) = 0 $$
I want to use finite elements to solve this ...
1
vote
0answers
58 views
Parallel dense solve with submatrices from mesh refinement with Petsc
For a Bounday Element Method problem I require the solution of a system of linear equations with multiple right-hand sides. Though this is a dense system, I still want to do it via Petsc in parallel. ...
1
vote
0answers
91 views
PETSc - difference between PetscNew and PetscMalloc
I wonder what is the difference between both functions.
In C++, the difference between new and malloc is easier: new allocates memory by calling the constructor.
What about PETSc ? In the example, ...
1
vote
1answer
388 views
Assembling sparse matrix in PETSC for Poisson equation
I am a novice at PETSC, and I have been trying to write an FVM code for steady heat conduction in 2D using PETSC (square, regular grid, Dirichlet boundaries)
Since the large matrix , say A, will be ...
0
votes
0answers
17 views
Orientation of cones and transitive closures of a dmplex in Petsc
From the Petsc manual pages, I fail to understand what the orientations of cones and transitive closures mean.
In particular, how can I relate these numbers to the orientation of the length/area/...
0
votes
1answer
37 views
Access PETSc data in totalview?
Is it possible to view the data stored in the various PETSc data types from within totalview?
Ordinarily, PETSc types are integers which act as pointers to the actual data (obviously my understanding ...
