[ET Trac] [Einstein Toolkit] #963: Improve McLachlan accuracy
Einstein Toolkit
trac-noreply at einsteintoolkit.org
Wed Jun 20 15:41:55 CDT 2012
#963: Improve McLachlan accuracy
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Reporter: eschnett | Owner:
Type: enhancement | Status: new
Priority: major | Milestone:
Component: EinsteinToolkit thorn | Version:
Keywords: |
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James van Meter provided me with an optimised version of McLachlan. He
states:
1. You are not taking full advantage of the chi=exp(-2phi) variable.
There are several terms you divide by chi or chi^2 in expressions with
overall factors exp(-4phi). I rewrote the BSSN equations to make these
cancellations before coding. So where you have an expression of the form
chi^2(A+B/chi^2), I have chi^2A+B. This gives a slight but noticeable
advantage in both accuracy and performance.
2. I added Hamiltonian-constraint-damping terms due to Duez et al. These
terms don't seem to be well-known but they are effective.
3. I added a Gamma-constraint-damping term due to Yo et al.
4. I enforce det(g)=1.
I have not tested this new version yet, but James suggests to include it
into the Einstein Toolkit.
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Ticket URL: <https://trac.einsteintoolkit.org/ticket/963>
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