Best way to register array parameters that can default to single scalar

[mcaroba]

I am trying to simplify the soap_turbo string and make it more soap-like. What would be the best way to call param_register() for a variable that is internally an array, but allowing the user to define it as a scalar (so that all the array elements would default to this scalar)?

Example, in soap_turbo the number of radial basis functions is defined for each element, if you have a soap descriptor with 3 species, you'd do something like n_max={10 8 9}. But imagine that you don't want or need to optimize the number of basis functions per species and just want all of them to use the same number by, e.g., defining n_max=9. Then the code would set n_max(1:3) = 9 either inside param_register() or in descriptors.f95 using some "flag" of information retrievable from param_register().

What would be the easiest, most "quipionic" way to go about this?

[bernstei]

The only way I can think of right now is a string, say comma separated, which you parse yourself (there might already be a split function you could use). We could implement a modification to the parser that array parameters can handle handle a single value input, and if so, set all array elements equal to it, but I don't think that happens now. And to the extent that these strings are expected to be the same format as the 2nd extxyz line (which is not necessarily going to remain true once we have the separate reader, unless we refactor it so it can be used for standalone strings) it'll break the consistency between fortran and python, because only in fortran are the array dimensions known before parsing.

[mcaroba]

Reading a string and then doing my own parsing was what I had in mind as fallback option, so I'll probably try that one out. I'll keep an eye for possible issues with quippy.

[gabor1]

have a look at how e0 is done - that can be set as a scalar, or as a string (which is then parsed into an array)

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On 14 Aug 2021, at 14:33, Miguel A. Caro ***@***.***> wrote: Reading a string and then doing my own parsing was what I had in mind as fallback option, so I'll probably try that one out. I'll keep an eye for possible issues with quippy. — You are receiving this because you are subscribed to this thread. Reply to this email directly, view it on GitHub, or unsubscribe. Triage notifications on the go with GitHub Mobile for iOS or Android.

[mcaroba]

This could be the solution, thanks. I will try to finalize the interface after this grant application frenzy is over, if I haven't lost my head by then!