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A few routines were updated to allow compiling and running split 4D-Var with mixed precision.

The split 4D-Var algorithms (like RBL4DVAR_SPLIT) recommend the mixed precision approach to accelerate computations. The executing script (see submit_split_rbl4dvar.sh) uses multiple ROMS executables, which runs the outer loop in double precision (nonlinear background trajectory, prior) and single precision in the inner loops (tangent linear and adjoint minimization, increment phase).

In this update, several of the variables needed by the RPCG solver are declared in double precision to reduce the impact of rounding error and the convergence of the minimization algorithm (rpcg_lanczos.F) when computing dot-products and Ritz eigenvalues and eigenvectors.

We use the real(dp) to declare specific internal variables in such cases. For example, in rpcg_lanczos.F, we have:

!
!  Local variable declarations.
!
      logical :: Ltrans, Laug
!
      integer :: i, ic, j, iobs, ivec, Lscale, info
!
      real(dp) :: zbet, eps, preducv, preducy
      real(dp) :: Jopt, Jf, Jmod, Jdata, Jb, Jobs, Jact, cff
!
      real(dp), dimension(NinnLoop) :: zu, zgam, zfact, ztemp3
      real(dp), dimension(NinnLoop) :: ztemp1, ztemp2, zu1, zu2
      real(dp), dimension(NinnLoop) :: ztemp4
      real(dp), dimension(Ndatum(ng)+1) :: px, pgrad, zw, zt
      real(dp), dimension(Ndatum(ng)+1) :: zhv, zht, zd
      real(dp), dimension(Ninner,3) :: zwork
      real(dp), dimension(2*(NinnLoop-1)) :: work
      real(dp), dimension(Ninner,Ninner) :: zgv

Many thanks to Pariza Heidary (NOAA) and Julia Levin for bringing this to my attention.

The bulk fluxes parameterization module was updated to the COARE 3.5 algorithm. For detailed documentation about this update, please check ​github.com/myroms/ROMS PR #35.

Many thanks to Fernando Pareja and John Wilkin for implementing and testing this update to bulk_flux.F.

• Starting January 1, 2025, ROMS will be distributed exclusively via GitHub. In preparation for that transition, this PR removes any linkage to the deprecated SVN repository. The .git_filters/id.smudge, written in Perl, will add the following line to each of the source code files:

  #include "cppdefs.h"
        MODULE wrt_his_mod
  !
  !git $Id: 180e8620 2024-07-10 19:39:12 UTC arango $
  !================================================== Hernan G. Arango ===
  !  Copyright (c) 2002-2024 The ROMS/TOMS Group                         !
  !    Licensed under a MIT/X style license                              !
  !    See License_ROMS.md                                               !
  !=======================================================================
  

• The smudge filter expands the !git $Id$ to include helpful information like:
  • Last eight characters of the git hash commit
  • Date of the commit in Universal Standard Time
  • Author of the commit modification

• If the user wants this information in their copy of the ROMS source code, you must force the smudge filter to run on the source code you downloaded. This takes several minutes but only needs to be done once:

      > git config filter.id.smudge ".git_filters/id.smudge %f"
      > git config filter.id.clean ".git_filters/id.clean %f"
      > rm .git/index
      > git checkout HEAD -- "$(git rev-parse --show-toplevel)"      (for bash shells)
      > git checkout HEAD -- "`git rev-parse --show-toplevel`"       (for csh/tcsh shells)
  

• Removed obsolete ROMS/Version.