Add relative error check in adaptive time stepping algorithm for rk23…

xfong commented 3 years ago

…, rk45dp and rk56 time steppers

godsic commented 3 years ago

@xfong

First of all, that you very much for the effort and for sharing this one with us.

Could you please

elaborate a bit on motivation for using relative error control;
provide some example .mx3 scripts where it helps overcome absolute error control limitations;
comment on what to expect performance- and precision-wise.

xfong commented 3 years ago

The adaptive time steeping control will benefit in cases where absolute errors of 1e-5 are much smaller than relTol * value of interest. This can help the transient simulation use larger time steps and hasten the completion of simulations.
The fixes are directly compatible with the existing .mx3 files with no modifications needed. The limitations on my side are that I do not have the tools to perform the benchmarking that you want and I suggest you can check the differences in runtimes on your set up. Also, it is more likely that the changes will benefit simulations that typically run for a long time.
At least 5% faster transient simulations are expected for simulations that typically take 30 minutes or longer to complete

Best,

Xuanyao (Kelvin) FONG

Assistant Professor

Department of Electrical & Computer Engineering, Faculty of Engineering

National University of Singapore

4 Engineering Drive 3

Singapore 117583

Office E4-05-23

Phone: +65-6516-6658

Fax: +65-6779-1103

Email: kelvin.xy.fong@nus.edu.sg

From: Mykola Dvornik notifications@github.com Sent: Wednesday, November 18, 2020 4:17 PM To: mumax/3 3@noreply.github.com Cc: xfong xuanyao.fong@gmail.com; Mention mention@noreply.github.com Subject: Re: [mumax/3] Add relative error check in adaptive time stepping algorithm for rk23… (#275)

First of all, that you very much for the effort and for sharing this one with us.

Could you please

elaborate a bit on motivation for using relative error control;
provide some example .mx3 scripts where it helps overcome absolute error control limitations;
comment on what to expect performance- and precision-wise.

godsic commented 3 years ago

@xfong

please be prepared for a long review process as this pull request touches very sensitive part of mumax3;
please restructure your code in a way, that using RelErr = 0 exactly follows the current code, while RelErr > 0 triggers your modifications.

xfong commented 3 years ago

I need to update the code in the branch to meet your requirements.

Best,

Xuanyao (Kelvin) FONG

Assistant Professor

Department of Electrical & Computer Engineering, Faculty of Engineering

National University of Singapore

4 Engineering Drive 3

Singapore 117583

Office E4-05-23

Phone: +65-6516-6658

Fax: +65-6779-1103

Email: kelvin.xy.fong@nus.edu.sg

From: Mykola Dvornik notifications@github.com Sent: Wednesday, November 18, 2020 6:26 PM To: mumax/3 3@noreply.github.com Cc: xfong xuanyao.fong@gmail.com; Mention mention@noreply.github.com Subject: Re: [mumax/3] Add relative error check in adaptive time stepping algorithm for rk23… (#275)

please be prepared for a long review process as this pull request touches very sensitive part of mumax3;
please restructure your code in a way, that using RelErr = 0 exactly follows the current code, while RelErr > 0 triggers your modifications.

mumax / 3