#527: Thorn Dissipation should have 9th order dissipation added -----------------------------------+---------------------------------------- Reporter: hinder | Owner: Type: enhancement | Status: new Priority: minor | Milestone: Component: EinsteinToolkit thorn | Version: Keywords: Dissipation | -----------------------------------+---------------------------------------- The current standard in BBH evolutions is to use 8th order accurate finite differencing with 9th order accurate dissipation. Thorn Dissipation currently only supports up to 7th order accurate dissipation, and should be extended to support 9th order.
#527: Thorn Dissipation should have 9th order dissipation added ------------------------------------+--------------------------------------- Reporter: hinder | Owner: Type: enhancement | Status: review Priority: minor | Milestone: Component: EinsteinToolkit thorn | Version: Resolution: | Keywords: Dissipation ------------------------------------+--------------------------------------- Changes (by eschnett):
* status: new => review
Comment:
Please review and add a test case.
#527: Thorn Dissipation should have 9th order dissipation added ------------------------------------+--------------------------------------- Reporter: hinder | Owner: Type: enhancement | Status: review Priority: minor | Milestone: Component: EinsteinToolkit thorn | Version: Resolution: | Keywords: Dissipation ------------------------------------+---------------------------------------
Comment (by knarf):
I didn't check the coefficients, but assuming they are ok, the patch looks ok. It would be nicer in general to split the 9th order patch from the patch introducing idx. Please apply after adding a test suite.
#527: Thorn Dissipation should have 9th order dissipation added ------------------------------------+--------------------------------------- Reporter: hinder | Owner: Type: enhancement | Status: review Priority: minor | Milestone: Component: EinsteinToolkit thorn | Version: Resolution: | Keywords: Dissipation ------------------------------------+---------------------------------------
Comment (by hinder):
I have checked the coefficients and they look correct. The only thing I don't understand is the convention for the dissipation strength. I don't get the 1/1024 factor (and by extension, the factors that appear in the existing orders). Do you have a reference for this? Is it a common convention? I compared with Gustafsson, Kreiss and Oliger (http://books.google.de/books?id=1JZ2mSQ- O6MC&lpg=PP1&ots=A9c4UBZBjl&dq=gustafsson+kreiss+oliger&pg=PA239&redir_esc=y#v=onepage&q=gustafsson%20kreiss%20oliger&f=false) top of p240 and when I compute that operator, I don't get the 1/1024 factor.
#527: Thorn Dissipation should have 9th order dissipation added ------------------------------------+--------------------------------------- Reporter: hinder | Owner: Type: enhancement | Status: closed Priority: minor | Milestone: Component: EinsteinToolkit thorn | Version: Resolution: fixed | Keywords: Dissipation ------------------------------------+--------------------------------------- Changes (by eschnett):
* status: review => closed * resolution: => fixed
Comment:
Committed.
#527: Thorn Dissipation should have 9th order dissipation added ------------------------------------+--------------------------------------- Reporter: hinder | Owner: Type: enhancement | Status: closed Priority: minor | Milestone: Component: EinsteinToolkit thorn | Version: Resolution: fixed | Keywords: Dissipation ------------------------------------+---------------------------------------
Comment (by eschnett):
I don't know where these factors arise, but I dimly recall a discussion about CFL conditions -- these factors are supposed to ensure that eps=O(1) (such as e.g. eps=0.1) is a good choice for all orders.
It seems that a factor of 1/4 is missing for the order=1 case.
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