ice_dyn_vp: fix #42

phil-blain · Aug 9, 2022 · ef5858e · ef5858e
1 parent d2e6e18
commit ef5858e
Showing 1 changed file with 10 additions and 0 deletions.
diff --git a/cicecore/cicedynB/dynamics/ice_dyn_vp.F90 b/cicecore/cicedynB/dynamics/ice_dyn_vp.F90
@@ -2709,6 +2709,7 @@ subroutine fgmres (zetax2   , etax2   , &
       real (kind=dbl_kind) :: &
          norm_residual   , & ! current L^2 norm of residual vector
          inverse_norm    , & ! inverse of the norm of a vector
+         norm_rhs        , & ! L^2 norm of right-hand-side vector
          nu, t               ! local temporary values
 
       integer (kind=int_kind) :: &
@@ -2748,6 +2749,15 @@ subroutine fgmres (zetax2   , etax2   , &
       arnoldi_basis_x = c0
       arnoldi_basis_y = c0
 
+      ! solution is zero if RHS is zero
+      norm_rhs = sqrt(global_sum_prod(bx(:,:,:), bx(:,:,:), distrb_info, field_loc_NEcorner) + &
+                      global_sum_prod(by(:,:,:), by(:,:,:), distrb_info, field_loc_NEcorner))
+      if (norm_rhs == c0) then
+         solx = bx
+         soly = by
+         return
+      endif
+
       ! Residual of the initial iterate
 
       !$OMP PARALLEL DO PRIVATE(iblk)