= PDAF_gather_obs_f = 

This page documents the routine `PDAF_gather_obs_f` of PDAF, which was introduced with PDAF V1.13.

In the local filters (LESKTF, LETKF, LSEIK, LNETF) this routine gathers the full observation vector dimension from process-local observation vectors of size dim_obs_p and returns the full vector.

The routine depends on [wiki:PDAF_gather_dim_obs_f], which defines the process-local observation dimensions. Further, the related routine [wiki:PDAF_gather_obs_f2] is used to gather the associated rank-2 array of observation coordinates. 

The routine is typically used in the routines [wiki:init_dim_obs_f_pdaf] and [wiki:obs_op_f_pdaf] if the analysis step of the local filters is parallelized.

The interface is the following:
{{{
  SUBROUTINE PDAF_gather__obs_f(obs_p, obs_f, status)
}}}
with the following arguments:
 * `obs_p` : `real, intent(in), dimension(dim_obs_p)`[[BR]] Process-local observation vector
 * `obs_f` : `real, intent(out), dimension(dim_obs_f)`[[BR]] Full observation vector
 * `status` : `integer, intent(out)`[[BR]] Status flag (0 for no error)

Notes:
 * The routine `PDAF_gather_dim_obs_f` has to be called once before using `PDAF_gather_obs_f` because it internally initializes the local observation dimensions for gathering. The most recent call to `PDAF_gather_dim_obs_f` defines the dimensions `dim_obs_p` and `dim_obs_f` used here.
 * For cases with different observation types, the routine [wiki:PDAF_gather_obs_f_flex] can be used. It does not rely on `PDAF_gather_dim_obs_f` and is hence easier to use. It was introduced in PDAF 1.14.