From 812dcd3462852c1ffbdaf1e6c17343e9c80b02fb Mon Sep 17 00:00:00 2001
From: Miles Curry <2590700+MiCurry@users.noreply.github.com>
Date: Wed, 11 Mar 2026 16:10:06 -0600
Subject: [PATCH] Add MPI routine to tell workers when a new iteration starts

This commit adds a new routine to Main_MPI that allows the main task to
communicate to workers that a new inversion iteration is starting. It currently
is not called anywhere in ModEM.

The workers keep track themselves of the iteration number. This routine is
intended to provide a space where the main task and all workers can coordinate
specific tasks. Specifically, this will allow us the ability to call
ModEM_memory_get_all to record all total memory usage across all tasks.
---
 f90/MPI/Main_MPI.f90 | 42 +++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 41 insertions(+), 1 deletion(-)

diff --git a/f90/MPI/Main_MPI.f90 b/f90/MPI/Main_MPI.f90
index e9adf8d6..625d3688 100644
--- a/f90/MPI/Main_MPI.f90
+++ b/f90/MPI/Main_MPI.f90
@@ -1455,6 +1455,40 @@ Subroutine Master_job_Distribute_userdef_control(ctrl, comm)
 
 end Subroutine Master_job_Distribute_userdef_control
 
+
+subroutine Master_job_send_inv_iteration(iteration_num, comm)
+
+    implicit none
+
+    integer, intent(in) :: iteration_num
+    integer, intent(in), optional :: comm
+    integer :: task, size_current, comm_current
+
+    if (present(comm)) then
+         if (comm .eq. MPI_COMM_NULL) then
+             comm_current = comm_world
+         else
+             comm_current = comm
+         endif
+     else
+         comm_current = comm_world
+     end if
+     call MPI_COMM_SIZE( comm_current, size_current, ierr )
+
+    worker_job_task % what_to_do = 'ITER_NUM'
+    worker_job_task % per_index = -1
+    worker_job_task % pol_index = -1
+    call create_worker_job_task_place_holder
+    call Pack_worker_job_task
+
+    do task = 1, size_current - 1
+        call MPI_SEND(worker_job_package, Nbytes, MPI_PACKED, task, FROM_MASTER, comm_current, ierr)
+    end do
+
+    write(0,*) "New Iteration: ", iteration_num
+
+end subroutine Master_job_send_inv_iteration
+
 !#########################  Master_job_Clean Memory ##########################
 Subroutine Master_job_Clean_Memory(comm)
 
@@ -1827,7 +1861,7 @@ Subroutine Worker_job(sigma,d)
    
      Integer                                :: iper,ipol,i,des_index
      Integer                                :: per_index,per_index_pre 
-     Integer                                :: pol_index, stn_index
+     Integer                                :: pol_index, stn_index, iteration_number
      Integer                                :: eAll_vec_size
      Integer                                :: comm_current, rank_current
      Integer                                :: cpu_only_ranks
@@ -1854,6 +1888,7 @@ Subroutine Worker_job(sigma,d)
        
      nTx=d%nTx
      recv_loop=0
+     iteration_number = 0
      previous_message=''
      write(node_info,'(a5,i3.3,a4)') 'node[',taskid,']:  '
 
@@ -2565,6 +2600,11 @@ Subroutine Worker_job(sigma,d)
              if (associated(group_sizes)) then 
                  deallocate(group_sizes) 
              endif
+         elseif (trim(worker_job_task%what_to_do) .eq. 'ITER_NUM' ) then
+
+            iteration_number = iteration_number + 1
+            write(0,*) "New Iteration: ", iteration_number
+
          elseif (trim(worker_job_task%what_to_do) .eq. 'STOP' ) then
              ! clear all the temp packages and stop
              if (associated(sigma_para_vec)) then