= Porting from PDAF2 to PDAF3 =

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PDAF V3.0 is not fully backward compatible with PDAF2. Modernizing the PDAF code motivated us to allow some changes which require code changes by the PDAF users. Thus, when switching from using PDAF2 to PDAF3, it is not possible to just compile the new PDAF library and link it with your code (in contrast to many previous releases). 

Here we explain the steps required to adapt your code to PDAF 3.

== Using PDAF3 with existing codes ==

To use existing assimilation code, we recommend the following steps. This relates for Fortran code.

* Include[[BR]] `USE PDAF`[[BR]] in all routines that call PDAF routines (e.g. in init_pdaf and assimilate_pdaf). 
* If you used `USE PDAF_interface_module` in your code, replace this by `USE PDAF`.
* You might need to adapt the Makefile of your program to include[[BR]]`-IPATH_TO_PDAF_INCLUDE`,[[BR]] where PATH_TO_PDAF_INCLUDE is the directory `include/` of your PDAF installation. The compiler needs to find the PDAF module files which are places in `include/`
* particular cases:
  *  If the compile process of your programm includes the compilation of PDAF using src/Makefile: With PDAF3 the Makefile is now only in the base-directory and there is no Makefile any more in src/. Thus, addapt to use the Makefile in the base-directory (alternatively you can copy this Makefile into src/ and adapt it according to the hints given inside the Makefile
  * If you used the offline mode by specifying **subtype=5**: change `subtype` to 0 and add a call to the routine `PDAF_set_offline_mode` in `init_pdaf`. (see, the example in the file `tutorial/offline_2D_serial/init_pdaf_offline.F90` where the call to `PDAF_set_offline_mode` is at the very end of the routine; see also [wiki:OfflineInitPdaf]).
  * If your code calls **PDAF_assimilate_lnetf** or **PDAF_put_state_lnetf**: There was an argument added for `init_obs_pdaf`. the code has to be adapted for this additional arguments. (see [wiki:PDAF_assimilate_lnetf] or [wiki:PDAF_put_state_lnetf])
  * If your code used the **SEEK filter**: This filter was deprecated for a longer time and is no longer available with PDAF V30. Any call to e.g. PDAF_assimilate_seek has to be removed.
  * If your code used the **'simplified interface'**, i.e. routines with ending `_si`: The `_si` routine are no longer present in PDAF V3.0. Instead use the full interface routine, i.e. the routine with the same name as the `_si` routine, but without `_si`. Then set the arguments to the names that you find inside the `_si` routine file from PDAF2.

With these adaptions, the compiling the program should be possible.

Two additional changes relate to the specification of `subtype` and the integer and real parameters for `PDAF_init`:
* A few of the parameters used to configure PDAF in the call to `PDAF_init` have changed their index. This only concerns the EnKF, LEnKF, LKNETF and PF. An overview of the parameters is show in the tables on the [wiki:AvailableOptionsforInitPDAFinPDAF3 page 'Available options for the different DA methods'].
* The values of `subtype` have been renumbered as follows
||= old subtype[[BR]]PDAF2 =||= new subtype[[BR]]PDAF3 =||
|| 0 || 0 (no change) ||
|| 1 || 1 (no change) ||
|| 2 || 10 ||
|| 3 || 11 ||
|| 4 || 2 ||
|| 5 || 5 (no longer offline mode) ||
|| 6 || 3 ||
|| 7 || 4 ||


== Porting to the PDAF3 interface ==

PDAF V3.0 also provides a set of new routines to call the analysis step, which we call the PDAF3 interface, because the calls are of the format `PDAF3_assimilate_` or `PDAF3_put_state_`. It is not required to switch to these new interface routines, but generally recommended. 

Details about the PDAF3 interface are provided on the [wiki:PDAF3_interface Page on the PDAF3 interface].

== Using new features of PDAF V3.0 ==

PDAF V3.0 also introduces several new features. An overview of these is given on the [wiki:PDAF3_new_functionality Page on new functionality on PDAF V3.0].