Skip to content
New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

SharpClaw with TVD limiting gives different results in serial and parallel #491

Open
ketch opened this issue Dec 22, 2014 · 2 comments
Open
Labels

Comments

@ketch
Copy link
Member

ketch commented Dec 22, 2014

@hadjimy and I have just verified that running the 2D acoustics example in serial and parallel gives different answers (relative error larger than 1e-3) when solver_type=sharpclaw and lim_type=1 (TVD limiting). When using WENO limiting (lim_type=2), the serial and parallel solutions agree to high accuracy.

We verified that running with MPI and PETSc but only one process gives results that match the serial results.

The differences seem also to depend on how many processors are used. My first guess is that somehow the TVD limiting is not behaving correctly in the ghost cells, though I don't see anything obvious in the code.

This bug exists already in master, but we don't have a test that triggers it. It is responsible for the failing test in #483.

@ketch ketch added the Bug label Dec 22, 2014
@ketch
Copy link
Member Author

ketch commented Dec 22, 2014

h/t to @hadjimy for discovering this.

@ketch
Copy link
Member Author

ketch commented Dec 22, 2014

One additional observation: the results from parallel runs of SharpClaw with TVD limiting seem to be non-deterministic; the values vary by several percent from one run to the next.

Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment
Labels
Projects
None yet
Development

No branches or pull requests

1 participant