From ada4117017ee3f905891ad107112e2f9ca3eca7c Mon Sep 17 00:00:00 2001
From: Trevor Ray Hillebrand <trhille@lanl.gov>
Date: Mon, 30 Oct 2023 12:55:20 -0600
Subject: [PATCH] Remove support for config_rk_order = 1

Remove support for config_rk_order = 1 to avoid unnecessary redundancy
with config_time_integration = forward_euler while maintaining
backward compatibility.
---
 components/mpas-albany-landice/src/Registry.xml               | 4 ++--
 .../src/mode_forward/mpas_li_time_integration_fe_rk.F         | 4 +---
 2 files changed, 3 insertions(+), 5 deletions(-)

diff --git a/components/mpas-albany-landice/src/Registry.xml b/components/mpas-albany-landice/src/Registry.xml
index e27c950b48ba..8232146c759f 100644
--- a/components/mpas-albany-landice/src/Registry.xml
+++ b/components/mpas-albany-landice/src/Registry.xml
@@ -489,8 +489,8 @@
 		            possible_values="'forward_euler' or 'runge_kutta'"
 		/>
                 <nml_option name="config_rk_order" type="integer" default_value="2" units="unitless"
-                            description="Order of Runge-Kutta time integration to use. A value of 1 is equivalent to forward euler. Values of 2 and 3 indicate strong-stability preserving RK2 and RK3. There is currently no support for classical RK2 or RK4 methods."
-                            possible_values="1, 2, 3"
+                            description="Order of Runge-Kutta time integration to use. A value of 1 would be equivalent to forward euler, but will cause an error to avoid unnecessary redundancy. Values of 2 and 3 indicate strong-stability preserving RK2 and RK3. There is currently no support for classical RK2 or RK4 methods."
+                            possible_values="2 or 3"
                 />
 		<nml_option name="config_rk3_stages" type="integer" default_value="3" units="stages"
                         description="Number of stages for strong stability preserving RK3 time integration. If set to 3, this involves 3 velocity solves and a maximum CFL fraction of 1. If set to 4, this involves 4 velocity solves, but the maximum CFL fraction is 2."
diff --git a/components/mpas-albany-landice/src/mode_forward/mpas_li_time_integration_fe_rk.F b/components/mpas-albany-landice/src/mode_forward/mpas_li_time_integration_fe_rk.F
index 25a141874b90..73f9223b6092 100644
--- a/components/mpas-albany-landice/src/mode_forward/mpas_li_time_integration_fe_rk.F
+++ b/components/mpas-albany-landice/src/mode_forward/mpas_li_time_integration_fe_rk.F
@@ -294,9 +294,7 @@ subroutine li_time_integrator_forwardeuler_rungekutta(domain, err)
                                       ! weights are updated for each case below
       rkTendWeights(:) = -9999.0_RKIND
       rkSubstepWeights(:) = -9999.0_RKIND
-      if ( (trim(config_time_integration) == 'forward_euler') .or. &
-           ((trim(config_time_integration) == 'runge_kutta') .and. &
-           (config_rk_order == 1)) ) then
+      if (trim(config_time_integration) == 'forward_euler') then
          nRKstages = 1
          rkSSPweights(1) = 1.0_RKIND
          rkTendWeights(1) = 1.0_RKIND