[gmx-developers] g_select empty selection

[Teemu Murtola]

Hi

On Fri, Feb 26, 2010 at 21:19, Michel Cuendet <michel.cuendet at isb-sib.ch> wrote:
> I think g_select is a great tool that had been missing in gromacs for a
> long time! I however stumbled on a weird behavior.
>
> [ clip ]
>
> The goal was to use the non-interacting waters stored in notinter to do
> some more elaborate selections. But if notinter is used further in the
> input file (as with the dummy line "test = notinter and heavy1"), the
> selection notinter becomes empty. So the input file above would give
> zero elements for notinter. If you remove the last line, the same input
> file gives the correct number of elements in notinter.

Thanks for reporting this. There was indeed a bug that caused
incorrect empty selections under certain conditions if there were many
inter-dependent variables in the selection. Could you please check if
the latest git version fixes your problem?

> PS: It would be great to be able to use in g_select a selection
> criterion similar to the one in g_hbond !

That might be coming at some point, but as the criterion is relatively
complex to implement efficiently and flexibly, I haven't had the time
to put much thought or effort into it. However, new selection criteria
are relatively straightforward to implement without understanding the
rest of the selection code in any detail, so contributed code is
welcome if someone else has more need for such a feature. :)

- Teemu