RINGS -- Too many 6-Membered Rings; Increase MAXRING

[ru80john]

Hello,

I recently ran MD simulation in a large system that contains 482288 atoms and encountered the issue mentioned in the title.

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 ###            Tinker  ---  Software Tools for Molecular Design            ###
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 ##               Copyright (c)  Jay William Ponder  1990-2024               ##
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 Enter Cartesian Coordinate File Name :  system.xyz

 RINGS  --  Too many 6-Membered Rings; Increase MAXRING

 Tinker is Unable to Continue; Terminating the Current Calculation

However, I noticed that Tinker can run a system with up to 1 million atoms so I think the number of atoms is not the issue.
I checked the source code called rings.f that it set maxring = 10000.

I have a few questions to ask:

1. Does the error mean I only need to modify the variable to a larger number?
2. Why choose 10000 as a default value? Does it have any meaning or just an arbitrary number?
3. Is there an upper limit of the maxring?

I've attached the XYZ file down below
test.txt

Any help would be greatly appreciated.

Thank you very much!

John

[jayponder]

(1) Yes, you only need to make the MAXRING parameter larger, and then recompile the Tinker package. I would suggest to not make it too much larger than what you need for your system.

(2) The value of 10000 is already quite large! It is essentially arbitrary and can be changed- but, again, you should not make it much larger than what you actually need.

(3) There is in principle no "upper limit", meaning there is nothing else in the code that places a maximum value on the number of rings. (As you note, there is a separate limit of 1 million on the total number of atoms via the MAXATOM parameter, and even that value could also be increased.)

Finally, I would say that the CPU Tinker8 code will be very slow for such large systems. If you intend to do production calculations, you should investigate the GPU-capable Tinker9 package which will be much faster for very big systems.