# PDAF_gather_dim_obs_f

This page documents the routine `PDAF_gather_dim_obs_f`

of PDAF, which was introduced with PDAF V1.13.

In the local filters (LESKTF, LETKF, LSEIK, LNETF) this routine gathers the total observation dimension from process-local observation dimensions and returns this dimension.

The routine has to be called once before using any of the routines PDAF_gather_obs_f or PDAF_gather_obs_f2. This is because it stores the information on the process-local observation dimensions to enable the gathering operations in the two other routines.

The routine is typically used in the routine init_dim_obs_f_pdaf if the analysis step of the local filters is parallelized.

The interface is the following:

SUBROUTINE PDAF_gather_dim_obs_f(dim_obs_p, dim_obs_f)

with the following arguments:

`dim_obs_p`

:`integer, intent(in)`

Process-local dimension of observation vector`dim_obs_f`

:`integer, intent(out)`

Full dimension of observation vector

Notes:

- It is allowed to compute
`PDAF_gather_dim_obs_f`

multiple times. However, the calls to`PDAF_gather_obs_f`

and`PDAF_gather_obs_f2`

will use the dimensions defined in the most recent call to`PDAF_gather_dim_obs_f`