PDAF_get_rndcount

This page documents the routine PDAF_get_rndcount of PDAF, which was introduced with PDAF V3.1.

This routine can be used to retrieve number of random number function calls for the generation of random matrices by PDAF_generate_rndmat used, e.g. in ensmeble methods with random rotation or by PDAF_sampleens.

PDAF uses the LAPACK function DLARNV to generate random numbers. This function uses a vector of 4 elements to specify the seed determining the random number (see also PDAF_set_seed). Since DLARNV returns a new seed value, which is then used at the next call, the number of calls determines random numbers. Thus, if one changes e.g. the size of the (local) state vector in ensemble methods with random transformation (like the LESTKF or LETKF with type_trans>0), the random number changes. This ill then change the analysis ensemble. The routine PDAF_get_rndcount can be used to determine if the number of random number calls remained unchanged between different runs.

The interface is:

  SUBROUTINE PDAF_get_rndcount(rndcount)

     INTEGER, INTENT(out) :: rndcount    ! Number of random value function calls