Together with a student of mine we are trying to use the CCZ4 formulation implemented in McLachlan. We saw that most parameters are the same as in BSSN, but there are damping factors that need to be selected.
In Alic et al 2013 (https://link.aps.org/doi/10.1103/PhysRevD.88.064049) they mention 3 damping factors (k1, k2, and k3), but in the param.ccl of McLachlan/ML_CCZ4 only k1 and k2 are mentioned (assuming they are the same).
Is it because k3 is hardcoded to the value suggested in Alic et al 2013? Or does McLachlan/ML_CCZ4 use a different set of evolution equations (in which case, is there a reference)?
We were able to find some example parameter files (for example the ones from the Parma group https://einstein.pr.infn.it/gravity/Research/BNS2015.html) and we found that they used indeed k1 and k2 from Alic et al 2013: ML_CCZ4::dampk1 = 0.05 ML_CCZ4::dampk2 = 0
We also saw that they added ML_CCZ4::ML_Theta to the Dissipation vars and set ML_CCZ4::apply_dissipation = "never". The other parameters look the same as when using BSSN.
Since I never used ML_CCZ4 I want to be sure that I'm setting the parameters correctly and the damping factors seem to be the most delicate point.
Thanks, Bruno
Bruno
Although I was probably around when the CCZ4 formulation was implemented, I don't recall.
I usually resolve to archaeology, comparing the equations in the respective Mathematica scripts to equations found in publications. If no one else speaks up, I can assist with this – we'd set up a Zoom meeting, and I can show how to read (or modify!) the Mathematica script that implements these equations.
-erik
On Tue, May 31, 2022 at 6:21 AM Bruno Giacomazzo bruno.giacomazzo@unimib.it wrote:
Together with a student of mine we are trying to use the CCZ4 formulation implemented in McLachlan. We saw that most parameters are the same as in BSSN, but there are damping factors that need to be selected.
In Alic et al 2013 (https://link.aps.org/doi/10.1103/PhysRevD.88.064049) they mention 3 damping factors (k1, k2, and k3), but in the param.ccl of McLachlan/ML_CCZ4 only k1 and k2 are mentioned (assuming they are the same).
Is it because k3 is hardcoded to the value suggested in Alic et al 2013? Or does McLachlan/ML_CCZ4 use a different set of evolution equations (in which case, is there a reference)?
We were able to find some example parameter files (for example the ones from the Parma group https://einstein.pr.infn.it/gravity/Research/BNS2015.html) and we found that they used indeed k1 and k2 from Alic et al 2013: ML_CCZ4::dampk1 = 0.05 ML_CCZ4::dampk2 = 0
We also saw that they added ML_CCZ4::ML_Theta to the Dissipation vars and set ML_CCZ4::apply_dissipation = "never". The other parameters look the same as when using BSSN.
Since I never used ML_CCZ4 I want to be sure that I'm setting the parameters correctly and the damping factors seem to be the most delicate point.
Thanks, Bruno
--
Prof. Bruno Giacomazzo Department of Physics University of Milano-Bicocca Piazza della Scienza 3 20126 Milano Italy
email: bruno.giacomazzo@unimib.it phone: (+39) 02 6448 2321 web: http://www.brunogiacomazzo.org
There are only 10 types of people in the world: Those who understand binary, and those who don't
Users mailing list Users@einsteintoolkit.org http://lists.einsteintoolkit.org/mailman/listinfo/users
Hi Erik, thanks a lot for the offer to help. I will try to have a look by myself first at the mathematica notebook.
Unless anybody else knows on what paper CCZ4 in McLachlan is based on. :-)
Cheers, Bruno
Il giorno mer 1 giu 2022 alle ore 22:48 Erik Schnetter schnetter@gmail.com ha scritto:
Bruno
Although I was probably around when the CCZ4 formulation was implemented, I don't recall.
I usually resolve to archaeology, comparing the equations in the respective Mathematica scripts to equations found in publications. If no one else speaks up, I can assist with this – we'd set up a Zoom meeting, and I can show how to read (or modify!) the Mathematica script that implements these equations.
-erik
On Tue, May 31, 2022 at 6:21 AM Bruno Giacomazzo bruno.giacomazzo@unimib.it wrote:
Together with a student of mine we are trying to use the CCZ4
formulation implemented in McLachlan. We saw that most parameters are the same as in BSSN, but there are damping factors that need to be selected.
In Alic et al 2013 (https://link.aps.org/doi/10.1103/PhysRevD.88.064049)
they mention 3 damping factors (k1, k2, and k3), but in the param.ccl of McLachlan/ML_CCZ4 only k1 and k2 are mentioned (assuming they are the same).
Is it because k3 is hardcoded to the value suggested in Alic et al 2013?
Or does McLachlan/ML_CCZ4 use a different set of evolution equations (in which case, is there a reference)?
We were able to find some example parameter files (for example the ones
from the Parma group https://einstein.pr.infn.it/gravity/Research/BNS2015.html) and we found that they used indeed k1 and k2 from Alic et al 2013:
ML_CCZ4::dampk1 = 0.05 ML_CCZ4::dampk2 = 0
We also saw that they added ML_CCZ4::ML_Theta to the Dissipation vars
and set
ML_CCZ4::apply_dissipation = "never". The other parameters look the same as when using BSSN.
Since I never used ML_CCZ4 I want to be sure that I'm setting the
parameters correctly and the damping factors seem to be the most delicate point.
Thanks, Bruno
--
Prof. Bruno Giacomazzo Department of Physics University of Milano-Bicocca Piazza della Scienza 3 20126 Milano Italy
email: bruno.giacomazzo@unimib.it phone: (+39) 02 6448 2321 web: http://www.brunogiacomazzo.org
There are only 10 types of people in the world: Those who understand binary, and those who don't
Users mailing list Users@einsteintoolkit.org http://lists.einsteintoolkit.org/mailman/listinfo/users
-- Erik Schnetter schnetter@gmail.com http://www.perimeterinstitute.ca/personal/eschnetter/
Hi Bruno,
I have gone through the notebook in the past and from what I could see, the version of paper I (10.1103/PhysRevD.85.064040) is implemented in the code, kappa_3 is encoded in the parameter 'ML_CCZ4::GammaShift', and the changes for the scaling of kappa_1 and kappa_2 with the lapse (eq. 27 and 28 in paper II, 2013) are not implemented.
I hope this helps. Best, Michael Müller ________________________________ From: users-bounces@einsteintoolkit.org users-bounces@einsteintoolkit.org on behalf of Bruno Giacomazzo bruno.giacomazzo@unimib.it Sent: Thursday, June 2, 2022 10:04 AM To: Erik Schnetter schnetter@gmail.com Cc: Einstein Toolkit Users users@einsteintoolkit.org; Paolo Garimberti p.garimberti@campus.unimib.it Subject: Re: [Users] question about ML_CCZ4 parameters
CAUTION: This email originated from outside of the University of Guelph. Do not click links or open attachments unless you recognize the sender and know the content is safe. If in doubt, forward suspicious emails to IThelp@uoguelph.ca
Hi Erik, thanks a lot for the offer to help. I will try to have a look by myself first at the mathematica notebook.
Unless anybody else knows on what paper CCZ4 in McLachlan is based on. :-)
Cheers, Bruno
Il giorno mer 1 giu 2022 alle ore 22:48 Erik Schnetter <schnetter@gmail.commailto:schnetter@gmail.com> ha scritto: Bruno
Although I was probably around when the CCZ4 formulation was implemented, I don't recall.
I usually resolve to archaeology, comparing the equations in the respective Mathematica scripts to equations found in publications. If no one else speaks up, I can assist with this – we'd set up a Zoom meeting, and I can show how to read (or modify!) the Mathematica script that implements these equations.
-erik
On Tue, May 31, 2022 at 6:21 AM Bruno Giacomazzo <bruno.giacomazzo@unimib.itmailto:bruno.giacomazzo@unimib.it> wrote:
Together with a student of mine we are trying to use the CCZ4 formulation implemented in McLachlan. We saw that most parameters are the same as in BSSN, but there are damping factors that need to be selected.
In Alic et al 2013 (https://link.aps.org/doi/10.1103/PhysRevD.88.064049) they mention 3 damping factors (k1, k2, and k3), but in the param.ccl of McLachlan/ML_CCZ4 only k1 and k2 are mentioned (assuming they are the same).
Is it because k3 is hardcoded to the value suggested in Alic et al 2013? Or does McLachlan/ML_CCZ4 use a different set of evolution equations (in which case, is there a reference)?
We were able to find some example parameter files (for example the ones from the Parma group https://einstein.pr.infn.it/gravity/Research/BNS2015.html) and we found that they used indeed k1 and k2 from Alic et al 2013: ML_CCZ4::dampk1 = 0.05 ML_CCZ4::dampk2 = 0
We also saw that they added ML_CCZ4::ML_Theta to the Dissipation vars and set ML_CCZ4::apply_dissipation = "never". The other parameters look the same as when using BSSN.
Since I never used ML_CCZ4 I want to be sure that I'm setting the parameters correctly and the damping factors seem to be the most delicate point.
Thanks, Bruno
--
Prof. Bruno Giacomazzo Department of Physics University of Milano-Bicocca Piazza della Scienza 3 20126 Milano Italy
email: bruno.giacomazzo@unimib.itmailto:bruno.giacomazzo@unimib.it phone: (+39) 02 6448 2321 web: http://www.brunogiacomazzo.org
There are only 10 types of people in the world: Those who understand binary, and those who don't
Users mailing list Users@einsteintoolkit.orgmailto:Users@einsteintoolkit.org http://lists.einsteintoolkit.org/mailman/listinfo/users
-- Erik Schnetter <schnetter@gmail.commailto:schnetter@gmail.com> http://www.perimeterinstitute.ca/personal/eschnetter/
--
Prof. Bruno Giacomazzo Department of Physics University of Milano-Bicocca Piazza della Scienza 3 20126 Milano Italy
email: bruno.giacomazzo@unimib.itmailto:bruno.giacomazzo@unimib.it phone: (+39) 02 6448 2321 web: http://www.brunogiacomazzo.orghttp://www.brunogiacomazzo.org/
---------------------------------------------------------------------- There are only 10 types of people in the world: Those who understand binary, and those who don't ----------------------------------------------------------------------
Hi all,
The CCZ4 code was written initially by Dana Alic. Erik (and others) subsequently made improvements since then. As far as I know, it should be effectively implementing the equations as in gr-qc:1106.2254.
With regards to the k3 parameter, Dana previously had this to say: "[GammaShift] should actually be 'real' and its default value set to 0.5, as it corresponds to the k3 parameter in the CCZ4 paper ( http://arxiv.org/pdf/1106.2254.pdf). This is important, because it leads to fast instabilities if it is set to 1 and coupled with non-zero values of the damping terms."
I hope this helps, Barry
On Thu, 2 Jun 2022 at 16:02, Michael Muller mullerm@uoguelph.ca wrote:
Hi Bruno,
I have gone through the notebook in the past and from what I could see, the version of paper I (10.1103/PhysRevD.85.064040) is implemented in the code, kappa_3 is encoded in the parameter ' ML_CCZ4::GammaShift', and the changes for the scaling of kappa_1 and kappa_2 with the lapse (eq. 27 and 28 in paper II, 2013) are not implemented.
I hope this helps. Best, Michael Müller
*From:* users-bounces@einsteintoolkit.org < users-bounces@einsteintoolkit.org> on behalf of Bruno Giacomazzo < bruno.giacomazzo@unimib.it> *Sent:* Thursday, June 2, 2022 10:04 AM *To:* Erik Schnetter schnetter@gmail.com *Cc:* Einstein Toolkit Users users@einsteintoolkit.org; Paolo Garimberti p.garimberti@campus.unimib.it *Subject:* Re: [Users] question about ML_CCZ4 parameters
CAUTION: This email originated from outside of the University of Guelph. Do not click links or open attachments unless you recognize the sender and know the content is safe. If in doubt, forward suspicious emails to IThelp@uoguelph.ca
Hi Erik, thanks a lot for the offer to help. I will try to have a look by myself first at the mathematica notebook.
Unless anybody else knows on what paper CCZ4 in McLachlan is based on. :-)
Cheers, Bruno
Il giorno mer 1 giu 2022 alle ore 22:48 Erik Schnetter < schnetter@gmail.com> ha scritto:
Bruno
Although I was probably around when the CCZ4 formulation was implemented, I don't recall.
I usually resolve to archaeology, comparing the equations in the respective Mathematica scripts to equations found in publications. If no one else speaks up, I can assist with this – we'd set up a Zoom meeting, and I can show how to read (or modify!) the Mathematica script that implements these equations.
-erik
On Tue, May 31, 2022 at 6:21 AM Bruno Giacomazzo bruno.giacomazzo@unimib.it wrote:
Together with a student of mine we are trying to use the CCZ4
formulation implemented in McLachlan. We saw that most parameters are the same as in BSSN, but there are damping factors that need to be selected.
In Alic et al 2013 (https://link.aps.org/doi/10.1103/PhysRevD.88.064049)
they mention 3 damping factors (k1, k2, and k3), but in the param.ccl of McLachlan/ML_CCZ4 only k1 and k2 are mentioned (assuming they are the same).
Is it because k3 is hardcoded to the value suggested in Alic et al 2013?
Or does McLachlan/ML_CCZ4 use a different set of evolution equations (in which case, is there a reference)?
We were able to find some example parameter files (for example the ones
from the Parma group https://einstein.pr.infn.it/gravity/Research/BNS2015.html) and we found that they used indeed k1 and k2 from Alic et al 2013:
ML_CCZ4::dampk1 = 0.05 ML_CCZ4::dampk2 = 0
We also saw that they added ML_CCZ4::ML_Theta to the Dissipation vars
and set
ML_CCZ4::apply_dissipation = "never". The other parameters look the same as when using BSSN.
Since I never used ML_CCZ4 I want to be sure that I'm setting the
parameters correctly and the damping factors seem to be the most delicate point.
Thanks, Bruno
--
Prof. Bruno Giacomazzo Department of Physics University of Milano-Bicocca Piazza della Scienza 3 20126 Milano Italy
email: bruno.giacomazzo@unimib.it phone: (+39) 02 6448 2321 web: http://www.brunogiacomazzo.org
There are only 10 types of people in the world: Those who understand binary, and those who don't
Users mailing list Users@einsteintoolkit.org http://lists.einsteintoolkit.org/mailman/listinfo/users
-- Erik Schnetter schnetter@gmail.com http://www.perimeterinstitute.ca/personal/eschnetter/
--
Prof. Bruno Giacomazzo Department of Physics University of Milano-Bicocca Piazza della Scienza 3 20126 Milano Italy
email: bruno.giacomazzo@unimib.it phone: (+39) 02 6448 2321 web: http://www.brunogiacomazzo.org
There are only 10 types of people in the world: Those who understand binary, and those who don't
Users mailing list Users@einsteintoolkit.org http://lists.einsteintoolkit.org/mailman/listinfo/users
Barry, thanks for the information!
Cheers, Bruno
Il giorno gio 9 giu 2022 alle ore 00:52 Barry Wardell < barry.wardell@gmail.com> ha scritto:
Hi all,
The CCZ4 code was written initially by Dana Alic. Erik (and others) subsequently made improvements since then. As far as I know, it should be effectively implementing the equations as in gr-qc:1106.2254.
With regards to the k3 parameter, Dana previously had this to say: "[GammaShift] should actually be 'real' and its default value set to 0.5, as it corresponds to the k3 parameter in the CCZ4 paper ( http://arxiv.org/pdf/1106.2254.pdf). This is important, because it leads to fast instabilities if it is set to 1 and coupled with non-zero values of the damping terms."
I hope this helps, Barry
On Thu, 2 Jun 2022 at 16:02, Michael Muller mullerm@uoguelph.ca wrote:
Hi Bruno,
I have gone through the notebook in the past and from what I could see, the version of paper I (10.1103/PhysRevD.85.064040) is implemented in the code, kappa_3 is encoded in the parameter ' ML_CCZ4::GammaShift', and the changes for the scaling of kappa_1 and kappa_2 with the lapse (eq. 27 and 28 in paper II, 2013) are not implemented.
I hope this helps. Best, Michael Müller
*From:* users-bounces@einsteintoolkit.org < users-bounces@einsteintoolkit.org> on behalf of Bruno Giacomazzo < bruno.giacomazzo@unimib.it> *Sent:* Thursday, June 2, 2022 10:04 AM *To:* Erik Schnetter schnetter@gmail.com *Cc:* Einstein Toolkit Users users@einsteintoolkit.org; Paolo Garimberti p.garimberti@campus.unimib.it *Subject:* Re: [Users] question about ML_CCZ4 parameters
CAUTION: This email originated from outside of the University of Guelph. Do not click links or open attachments unless you recognize the sender and know the content is safe. If in doubt, forward suspicious emails to IThelp@uoguelph.ca
Hi Erik, thanks a lot for the offer to help. I will try to have a look by myself first at the mathematica notebook.
Unless anybody else knows on what paper CCZ4 in McLachlan is based on. :-)
Cheers, Bruno
Il giorno mer 1 giu 2022 alle ore 22:48 Erik Schnetter < schnetter@gmail.com> ha scritto:
Bruno
Although I was probably around when the CCZ4 formulation was implemented, I don't recall.
I usually resolve to archaeology, comparing the equations in the respective Mathematica scripts to equations found in publications. If no one else speaks up, I can assist with this – we'd set up a Zoom meeting, and I can show how to read (or modify!) the Mathematica script that implements these equations.
-erik
On Tue, May 31, 2022 at 6:21 AM Bruno Giacomazzo bruno.giacomazzo@unimib.it wrote:
Together with a student of mine we are trying to use the CCZ4
formulation implemented in McLachlan. We saw that most parameters are the same as in BSSN, but there are damping factors that need to be selected.
In Alic et al 2013 (https://link.aps.org/doi/10.1103/PhysRevD.88.064049)
they mention 3 damping factors (k1, k2, and k3), but in the param.ccl of McLachlan/ML_CCZ4 only k1 and k2 are mentioned (assuming they are the same).
Is it because k3 is hardcoded to the value suggested in Alic et al
2013? Or does McLachlan/ML_CCZ4 use a different set of evolution equations (in which case, is there a reference)?
We were able to find some example parameter files (for example the ones
from the Parma group https://einstein.pr.infn.it/gravity/Research/BNS2015.html) and we found that they used indeed k1 and k2 from Alic et al 2013:
ML_CCZ4::dampk1 = 0.05 ML_CCZ4::dampk2 = 0
We also saw that they added ML_CCZ4::ML_Theta to the Dissipation vars
and set
ML_CCZ4::apply_dissipation = "never". The other parameters look the same as when using BSSN.
Since I never used ML_CCZ4 I want to be sure that I'm setting the
parameters correctly and the damping factors seem to be the most delicate point.
Thanks, Bruno
--
Prof. Bruno Giacomazzo Department of Physics University of Milano-Bicocca Piazza della Scienza 3 20126 Milano Italy
email: bruno.giacomazzo@unimib.it phone: (+39) 02 6448 2321 web: http://www.brunogiacomazzo.org
There are only 10 types of people in the world: Those who understand binary, and those who don't
Users mailing list Users@einsteintoolkit.org http://lists.einsteintoolkit.org/mailman/listinfo/users
-- Erik Schnetter schnetter@gmail.com http://www.perimeterinstitute.ca/personal/eschnetter/
--
Prof. Bruno Giacomazzo Department of Physics University of Milano-Bicocca Piazza della Scienza 3 20126 Milano Italy
email: bruno.giacomazzo@unimib.it phone: (+39) 02 6448 2321 web: http://www.brunogiacomazzo.org
There are only 10 types of people in the world: Those who understand binary, and those who don't
Users mailing list Users@einsteintoolkit.org http://lists.einsteintoolkit.org/mailman/listinfo/users
Dear Bruno,
contrary to Erik, I was not around when ML_CCZ4 was implemented, but I used it (or tried to use it) rather extensively.
Regarding the parameter named k3 in the papers, I'm pretty sure that's the one named GammaShift in the code. It is not hard coded, you can change it in the parfile, but its default value is 0.5 . As noted in the two original CCZ4 papers, this value breaks the covariance of the system (it should be set to 1. for it to be restored), but it allows to handle BH singularities.
The values of 0.05 and 0 for k1 and k2 (which do correspond to the k1 and k2 of the papers) are "standard" as far as I can tell. Another value I've seen a lot in parfiles for k1 is 0.036, while as far as I know k2 has always been set to 0. I cannot recall any real difference in BNS runs with k1=0.05 or k1=0.036, but I never tried to systematically tune these parameters to "optimal" values.
Finally, I want to note that I had a lot of subtle problems in using ML_CCZ4 that made me switch to ML_BSSN. These would not be outright crashes, but larger than expected oscillations of stars that in the long term made some simulations unusable to get realistic data, despite the GR constraints violations being much lower than ML_BSSN. When I first encountered this problem, I somehow got the impression that they might be related to some conflict with boundary conditions, but now I'm starting to think that they are related to the values of k1, k2 and k3 not being tuned properly, or maybe even by the system not being strongly hyperbolic (note that as far as I know, there is no actual proof of strong hyperbolicity for the original version of CCZ4 as implemented in McLachaln in the literature. Other versions of the system have been proved hyperbolic, but not this one).
Actually, if you and your student took the time to do some tuning and managed to improve the performance of this code, that would be pretty interesting in its own right, I think.
I hope this was of some help.
Best, Federico
Michael and Federico, thanks a lot for your emails. This information is very helpful.
Cheers, Bruno
Il giorno gio 2 giu 2022 alle ore 16:30 Federico Guercilena < guercilena.federico@gmail.com> ha scritto:
Dear Bruno,
contrary to Erik, I was not around when ML_CCZ4 was implemented, but I used it (or tried to use it) rather extensively.
Regarding the parameter named k3 in the papers, I'm pretty sure that's the one named GammaShift in the code. It is not hard coded, you can change it in the parfile, but its default value is 0.5 . As noted in the two original CCZ4 papers, this value breaks the covariance of the system (it should be set to 1. for it to be restored), but it allows to handle BH singularities.
The values of 0.05 and 0 for k1 and k2 (which do correspond to the k1 and k2 of the papers) are "standard" as far as I can tell. Another value I've seen a lot in parfiles for k1 is 0.036, while as far as I know k2 has always been set to 0. I cannot recall any real difference in BNS runs with k1=0.05 or k1=0.036, but I never tried to systematically tune these parameters to "optimal" values.
Finally, I want to note that I had a lot of subtle problems in using ML_CCZ4 that made me switch to ML_BSSN. These would not be outright crashes, but larger than expected oscillations of stars that in the long term made some simulations unusable to get realistic data, despite the GR constraints violations being much lower than ML_BSSN. When I first encountered this problem, I somehow got the impression that they might be related to some conflict with boundary conditions, but now I'm starting to think that they are related to the values of k1, k2 and k3 not being tuned properly, or maybe even by the system not being strongly hyperbolic (note that as far as I know, there is no actual proof of strong hyperbolicity for the original version of CCZ4 as implemented in McLachaln in the literature. Other versions of the system have been proved hyperbolic, but not this one).
Actually, if you and your student took the time to do some tuning and managed to improve the performance of this code, that would be pretty interesting in its own right, I think.
I hope this was of some help.
Best, Federico
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