= PDAF_init = This page documents the routine PDAF_init of PDAF. In `init_pdaf` the variables for the call to `PDAF_init` are set. The call to `PDAF_init` has the following structure: {{{ CALL PDAF_init(filtertype, subtype, step_null, & filter_param_i, length_filter_param_i, & filter_param_r, length_filter_param_r, & COMM_model, COMM_filter, COMM_couple, & task_id, n_modeltasks, filterpe, & U_init_ens, screen, status_pdaf) }}} The required variables are the following: * `filtertype`: An integer defining the type of filter algorithm. Available are * 0: SEEK * 1: SEIK * 2: EnKF * 3: LSEIK * 4: ETKF * 5: LETKF * 6: ESTKF * 7: LESTKF * `subtype`: An integer defining the sub-type of the filter algorithm (see the example code in `testsuite/src/dummymodel_1D` for choices). If `PDAF_init` is called with `subtype=-1` the available options are shown for the selected filter algorithm. * `step_null`: An integer defining the initial time step. For some cases it can use useful to set `step_null` larger to 0. * `filter_param_i`: Integer array collecting several variables for PDAF. The first two variables are mandatory and equal for all filters. Further variables are optional (see example code or use `subtype=-1` to display available options.). The mandatory variables are in the following order: * The size of the local state vector for the current process. * The ensemble size for all ensemble-based filters (or the rank of the state covariance matrix for mode-based filters like SEEK) * `length_filter_param_i`: An Integer defining the length of the array `filter_param_i`. The entries in the array are parsed up to this index. * `filter_param_r`: Array of reals collecting floating point variables for PDAF. The first variable is mandatory and equal for all filters. Further variables are optional (see example code in `testsuite/src/dummymodel_1D` or use `subtype=-1` to display available options.). The mandatory variable is: * The value of the forgetting factor controlling covariance inflation (required to be larger than zero; common are values between 0.9 and 1.0. For 1.0 the ensemble is not inflated.) * `length_filter_param_r`: An Integer defining the length of the array `filter_param_r`. The entries in the array are parsed up to this index. * `COMM_model`: The communicator variable `COMM_model` as initialized by `init_parallel_pdaf`. (Usually stored in the module `mod_assimilation`) * `COMM_filter`: The communicator variable `COMM_filter` as initialized by `init_parallel_pdaf`. (Usually stored in the module `mod_assimilation`) * `COMM_couple`: The communicator variable `COMM_couple` as initialized by `init_parallel_pdaf`. (Usually stored in the module `mod_assimilation`) * `task_id`: The index of the model tasks as initialized by `init_parallel_pdaf`. (Usually stored in the module `mod_assimilation`) * `n_modeltasks`: The number of model tasks as defined before the call to `init_parallel_pdaf`. (Usually stored in the module `mod_assimilation`) * `filterpe`: A logical flag showing whether a process belongs to `COMM_filter` as initialized by `init_parallel_pdaf`. (Usually stored in the module `mod_assimilation`) * `U_init_ens`: The name of the user-supplied routine that is called by `PDAF_init` to initialize the ensemble of model states. (See '[InsertAnalysisStep#User-suppliedroutineU_init_ensinit_ens_pdaf.F90 User-supplied routine U_init_ens]' * `screen`: An integer defining whether information output is written to the screen (i.e. standard output). The following choices are available: * 0: quiet mode - no information is displayed. * 1: Display standard information (recommended) * 2: as 1 plus display of timing information during the assimilation process * 3: Display detailed information for debugging * `status_pdaf`: An integer used as status flag of PDAF. If `status_pdaf` is zero upon exit from `PDAF_init` the initialization was successful. An error occurred for non-zero values. (The error codes are documented in the routine `PDAF_init`.) An overview of available options for each filter an be found on the [wiki:AvailableOptionsforInitPDAF overview page on options]. It is recommended that the value of `status_pdaf` is checked in the program after PDAF_init is executed. Only if its value is 0 the initialization was successful. PDAF also has a [PdafSimplifiedInterface Simplified Interface] providing the routine `PDAF_init_si`. In the simplified interface, the name of the user-supplied routine `U_init_ens` is predefined to `init_ens_pdaf` such that it does not appear in the call to `PDAF_init_si`. More information on the pre-defined names is provided in the [PdafSimplifiedInterface documentation of PDAF's simplified interface].