From fc53040e7861681ac9f9614361cf87c36874ccfb Mon Sep 17 00:00:00 2001
From: Jesse Nusbaumer <nusbaume@ucar.edu>
Date: Wed, 12 Jun 2024 15:01:44 -0600
Subject: [PATCH] Add new timestep number variable and root processor check.

---
 src/data/registry.xml      |  8 +++++++-
 src/utils/time_manager.F90 | 17 +++++++++++++----
 2 files changed, 20 insertions(+), 5 deletions(-)

diff --git a/src/data/registry.xml b/src/data/registry.xml
index c9dd29e7..3d8b5bc0 100644
--- a/src/data/registry.xml
+++ b/src/data/registry.xml
@@ -313,12 +313,18 @@
               phys_timestep_init_zero="true">
       <long_name>Total tendency from physics suite</long_name>
     </variable>
-    <!-- Physics timestep -->
+    <!-- Timestep variables -->
     <variable local_name="dtime_phys"
               standard_name="timestep_for_physics"
               units="s" type="real" kind="kind_phys">
       <long_name>timestep for physics</long_name>
     </variable>
+    <variable local_name="nstep"
+              standard_name="current_timestep_number"
+              units="count" type="integer">
+      <long_name>current timestep number</long_name>
+      <initial_value>0</initial_value>
+    </variable>
     <!-- Error handling variables -->
     <variable local_name="errcode"
               standard_name="ccpp_error_code"
diff --git a/src/utils/time_manager.F90 b/src/utils/time_manager.F90
index f57c5b9a..803a47e9 100644
--- a/src/utils/time_manager.F90
+++ b/src/utils/time_manager.F90
@@ -521,7 +521,11 @@ subroutine advance_timestep()
 ! Increment the timestep number.
 
 ! Use statements
-   use string_utils, only: stringify
+   use ESMF,          only: ESMF_ClockAdvance
+   use cam_logfile,   only: iulog
+   use physics_types, only: nstep
+   use spmd_utils,    only: masterproc
+   use string_utils,  only: stringify
 
 ! Local variables
    character(len=*), parameter :: sub = 'advance_timestep'
@@ -531,11 +535,16 @@ subroutine advance_timestep()
    call ESMF_ClockAdvance( tm_clock, rc=rc )
    call chkrc(rc, sub//': error return from ESMF_ClockAdvance')
 
+! Set current timestep number for use in CCPP physics schemes:
+   nstep = get_nstep()
+
 ! Write new timestep to CAM log file.
 
-   write(iulog,*) '------------------------'
-   write(iulog,*) 'CAM-SIMA time step advanced (nstep = '//stringify([get_nstep()])//')'
-   write(iulog,*) '------------------------'
+   if (masterproc) then
+      write(iulog,*) '------------------------'
+      write(iulog,*) 'CAM-SIMA time step advanced (nstep = '//stringify([nstep])//')'
+      write(iulog,*) '------------------------'
+   end if
 
 ! Set first step flag off.