compute ID count id1 id2 ...
compute 1 count species compute Ncounts count N N2 N+ air/O
Define a computation that counts the number of particles currently in the simulation for various species or groups within mixtures. Groups are collections of one or more species within a mixture. See the "mixture" command for an explanation of how species are added to a mixture and how groups of species within the mixture are defined.
Each of the listed ids (id1, id2, etc) can be in one of three formats. Any of the ids can be in any of the formats.
An id can be a species ID, in which case the count is for particles of that species.
An id can be a mixture ID, in which case one count is performed for each of the groups within the mixture. In the first example above, "species" is the name of a default mixture which assigns every species defined for the simulation to its own group. If there are 10 species in the simulation, there will thus be 10 counts calculated, the same as if the command had been specified with explicit names for all 10 species, e.g.
compute 1 count O2 N2 O N NO O2+ N2+ O+ N+ NO+
An id can also be of the form mix-ID/name where mix-ID is a mixture ID and name is the name of a group in that mixture.
If there is a single count accumulated, this compute calculates a global scalar. If there are multiple counts accumulated, it calculates a global vector with a length = number of counts. These results can be used by any command that uses global scalar or vector values from a compute as input. See Section 4.4 for an overview of SPARTA output options.
The values will all be unitless counts.
It is an error if a listed id is both a species ID and a mixture ID, since this command cannot distinguish between them.
Related commands: none