diff --git a/ocaml/TaskServer.ml b/ocaml/TaskServer.ml
index 45b438f2..68fa133f 100644
--- a/ocaml/TaskServer.ml
+++ b/ocaml/TaskServer.ml
@@ -41,7 +41,7 @@ let debug_env =
 
 let debug str =
   if debug_env then
-    Printf.printf "TASK : %s%!" str
+    Printf.eprintf "TASK : %s%!" str
 
 
 
diff --git a/plugins/Full_CI_ZMQ/run_pt2_slave.irp.f b/plugins/Full_CI_ZMQ/run_pt2_slave.irp.f
index 7cfcb91d..92ba5b7b 100644
--- a/plugins/Full_CI_ZMQ/run_pt2_slave.irp.f
+++ b/plugins/Full_CI_ZMQ/run_pt2_slave.irp.f
@@ -30,7 +30,7 @@ subroutine run_pt2_slave(thread,iproc,energy)
   zmq_socket_push      = new_zmq_push_socket(thread)
   call connect_to_taskserver(zmq_to_qp_run_socket,worker_id,thread)
   if(worker_id == -1) then
-    print *, "WORKER -1"
+    print *, 'WORKER -1'
     call end_zmq_to_qp_run_socket(zmq_to_qp_run_socket)
     call end_zmq_push_socket(zmq_socket_push,thread)
     return
@@ -62,7 +62,7 @@ subroutine run_pt2_slave(thread,iproc,energy)
     endif
 
     if(done .or. (ctask == size(task_id)) ) then
-      if(buf%N == 0 .and. ctask > 0) stop "uninitialized selection_buffer"
+      if(buf%N == 0 .and. ctask > 0) stop 'uninitialized selection_buffer'
       do i=1, ctask
          call task_done_to_taskserver(zmq_to_qp_run_socket,worker_id,task_id(i))
       end do
@@ -97,26 +97,30 @@ subroutine push_pt2_results(zmq_socket_push, N, index, pt2_detail, task_id, ntas
 
 
   rc = f77_zmq_send( zmq_socket_push, N, 4, ZMQ_SNDMORE)
-  if(rc /= 4) stop "push"
+  if(rc /= 4) stop 'push'
 
   rc = f77_zmq_send( zmq_socket_push, index, 4, ZMQ_SNDMORE)
-  if(rc /= 4*N) stop "push"
+  if(rc /= 4*N) stop 'push'
 
 
   rc = f77_zmq_send( zmq_socket_push, pt2_detail, 8*N_states*N, ZMQ_SNDMORE)
-  if(rc /= 8*N_states*N) stop "push"
+  if(rc /= 8*N_states*N) stop 'push'
 
   rc = f77_zmq_send( zmq_socket_push, ntask, 4, ZMQ_SNDMORE)
-  if(rc /= 4) stop "push"
+  if(rc /= 4) stop 'push'
 
   rc = f77_zmq_send( zmq_socket_push, task_id, ntask*4, 0)
-  if(rc /= 4*ntask) stop "push"
+  if(rc /= 4*ntask) stop 'push'
 
 ! Activate is zmq_socket_push is a REQ
 IRP_IF ZMQ_PUSH
 IRP_ELSE
   character*(2) :: ok
   rc = f77_zmq_recv( zmq_socket_push, ok, 2, 0)
+  if ((rc /= 2).and.(ok(1:2) /= 'ok')) then
+    print *,  irp_here//': error in receiving ok'
+    stop -1
+  endif
 IRP_ENDIF
 
 end subroutine
@@ -133,24 +137,28 @@ subroutine pull_pt2_results(zmq_socket_pull, N, index, pt2_detail, task_id, ntas
   integer :: rc, rn, i
 
   rc = f77_zmq_recv( zmq_socket_pull, N, 4, 0)
-  if(rc /= 4) stop "pull"
+  if(rc /= 4) stop 'pull'
 
   rc = f77_zmq_recv( zmq_socket_pull, index, 4, 0)
-  if(rc /= 4*N) stop "pull"
+  if(rc /= 4*N) stop 'pull'
 
   rc = f77_zmq_recv( zmq_socket_pull, pt2_detail, N_states*8*N, 0)
-  if(rc /= 8*N_states*N) stop "pull"
+  if(rc /= 8*N_states*N) stop 'pull'
 
   rc = f77_zmq_recv( zmq_socket_pull, ntask, 4, 0)
-  if(rc /= 4) stop "pull"
+  if(rc /= 4) stop 'pull'
 
   rc = f77_zmq_recv( zmq_socket_pull, task_id, ntask*4, 0)
-  if(rc /= 4*ntask) stop "pull"
+  if(rc /= 4*ntask) stop 'pull'
 
 ! Activate is zmq_socket_pull is a REP
 IRP_IF ZMQ_PUSH
 IRP_ELSE
   rc = f77_zmq_send( zmq_socket_pull, 'ok', 2, 0)
+  if (rc /= 2) then
+    print *,  irp_here//': error in sending ok'
+    stop -1
+  endif
 IRP_ENDIF
 
 end subroutine
diff --git a/plugins/Full_CI_ZMQ/run_selection_slave.irp.f b/plugins/Full_CI_ZMQ/run_selection_slave.irp.f
index d6f5739f..59b92b0d 100644
--- a/plugins/Full_CI_ZMQ/run_selection_slave.irp.f
+++ b/plugins/Full_CI_ZMQ/run_selection_slave.irp.f
@@ -132,7 +132,12 @@ subroutine push_selection_results(zmq_socket_push, pt2, b, task_id, ntask)
 ! Activate is zmq_socket_push is a REQ
 IRP_IF ZMQ_PUSH
 IRP_ELSE
-  rc = f77_zmq_recv( zmq_socket_push, task_id(1), ntask*4, 0)
+  character*(2) :: ok
+  rc = f77_zmq_recv( zmq_socket_push, ok, 2, 0)
+  if ((rc /= 2).and.(ok(1:2) /= 'ok')) then
+    print *,  irp_here//': error in receiving ok'
+    stop -1
+  endif
 IRP_ENDIF
 
 end subroutine
@@ -186,9 +191,12 @@ subroutine pull_selection_results(zmq_socket_pull, pt2, val, det, N, task_id, nt
 ! Activate is zmq_socket_pull is a REP
 IRP_IF ZMQ_PUSH
 IRP_ELSE
-  rc = f77_zmq_send( zmq_socket_pull, task_id(1), ntask*4, 0)
+  rc = f77_zmq_send( zmq_socket_pull, 'ok', 2, 0)
+  if (rc /= 2) then
+    print *,  irp_here//': error in sending ok'
+    stop -1
+  endif
 IRP_ENDIF
-
 end subroutine
  
  
diff --git a/plugins/MPI/broadcast.irp.f b/plugins/MPI/broadcast.irp.f
index 0662052b..148a81b1 100644
--- a/plugins/MPI/broadcast.irp.f
+++ b/plugins/MPI/broadcast.irp.f
@@ -10,9 +10,8 @@ subroutine broadcast_chunks_$double(A, LDA)
 ! Broadcast with chunks of ~2GB
   END_DOC
   integer :: i, sze, ierr
-  do i=1,LDA,2000000000/$8
-    sze = min(LDA-i+1, 2000000000/$8)
-!    call MPI_BARRIER(MPI_COMM_WORLD)
+  do i=1,LDA,200000000/$8
+    sze = min(LDA-i+1, 200000000/$8)
     call MPI_BCAST (A(i), sze, MPI_$DOUBLE_PRECISION, 0, MPI_COMM_WORLD, ierr)
     if (ierr /= MPI_SUCCESS) then
       print *,  irp_here//': Unable to broadcast chuks $double ', i
@@ -44,21 +43,18 @@ subroutine mpi_bcast_psi(energy, size_energy)
     include 'mpif.h'
     integer :: ierr
 
-!    call MPI_BARRIER(MPI_COMM_WORLD)
     call MPI_BCAST (N_states, 1, MPI_INTEGER, 0, MPI_COMM_WORLD, ierr)
     if (ierr /= MPI_SUCCESS) then
       print *,  irp_here//': Unable to broadcast N_states'
       stop -1
     endif
 
-!    call MPI_BARRIER(MPI_COMM_WORLD)
     call MPI_BCAST (N_det, 1, MPI_INTEGER, 0, MPI_COMM_WORLD, ierr)
     if (ierr /= MPI_SUCCESS) then
       print *,  irp_here//': Unable to broadcast N_det'
       stop -1
     endif
 
-!    call MPI_BARRIER(MPI_COMM_WORLD)
     call MPI_BCAST (psi_det_size, 1, MPI_INTEGER, 0, MPI_COMM_WORLD, ierr)
     if (ierr /= MPI_SUCCESS) then
       print *,  irp_here//': Unable to broadcast psi_det_size'
@@ -78,7 +74,6 @@ subroutine mpi_bcast_psi(energy, size_energy)
       TOUCH psi_det psi_coef
     endif
 
-!    call MPI_BARRIER(MPI_COMM_WORLD)
     call MPI_BCAST (N_det_generators, 1, MPI_INTEGER, 0, MPI_COMM_WORLD, ierr)
     if (ierr /= MPI_SUCCESS) then
       print *,  irp_here//': Unable to broadcast N_det_generators'
@@ -89,7 +84,6 @@ subroutine mpi_bcast_psi(energy, size_energy)
       TOUCH N_det_generators
     endif
 
-!    call MPI_BARRIER(MPI_COMM_WORLD)
     call MPI_BCAST (N_det_selectors, 1, MPI_INTEGER, 0, MPI_COMM_WORLD, ierr)
     if (ierr /= MPI_SUCCESS) then
       print *,  irp_here//': Unable to broadcast N_det_selectors'
@@ -100,13 +94,11 @@ subroutine mpi_bcast_psi(energy, size_energy)
       TOUCH N_det_selectors
     endif
 
-!    call MPI_BARRIER(MPI_COMM_WORLD)
     call MPI_BCAST (energy, size(energy), MPI_DOUBLE_PRECISION, 0, MPI_COMM_WORLD, ierr)
     if (ierr /= MPI_SUCCESS) then
       print *,  irp_here//': Unable to broadcast energy'
       stop -1
     endif
-!    call MPI_BARRIER(MPI_COMM_WORLD)
 
   IRP_ENDIF
 end
diff --git a/src/Davidson/NEEDED_CHILDREN_MODULES b/src/Davidson/NEEDED_CHILDREN_MODULES
index eb438a3c..aae89501 100644
--- a/src/Davidson/NEEDED_CHILDREN_MODULES
+++ b/src/Davidson/NEEDED_CHILDREN_MODULES
@@ -1 +1 @@
-Determinants MPI
+Determinants
diff --git a/src/Davidson/davidson_parallel.irp.f b/src/Davidson/davidson_parallel.irp.f
index 24f2f947..a6af704a 100644
--- a/src/Davidson/davidson_parallel.irp.f
+++ b/src/Davidson/davidson_parallel.irp.f
@@ -38,7 +38,7 @@ subroutine davidson_run_slave(thread,iproc)
   zmq_socket_push      = new_zmq_push_socket(thread)
   call connect_to_taskserver(zmq_to_qp_run_socket,worker_id,thread)
   if(worker_id == -1) then
-    print *, "WORKER -1"
+    print *, 'WORKER -1'
     call end_zmq_to_qp_run_socket(zmq_to_qp_run_socket)
     call end_zmq_push_socket(zmq_socket_push,thread)
     return
@@ -160,28 +160,28 @@ subroutine davidson_push_results(zmq_socket_push, v_t, s_t, imin, imax, task_id)
   sz = (imax-imin+1)*N_states_diag
 
   rc = f77_zmq_send( zmq_socket_push, task_id, 4, ZMQ_SNDMORE)
-  if(rc /= 4) stop "davidson_push_results failed to push task_id"
+  if(rc /= 4) stop 'davidson_push_results failed to push task_id'
 
   rc = f77_zmq_send( zmq_socket_push, imin, 4, ZMQ_SNDMORE)
-  if(rc /= 4) stop "davidson_push_results failed to push imin"
+  if(rc /= 4) stop 'davidson_push_results failed to push imin'
 
   rc = f77_zmq_send( zmq_socket_push, imax, 4, ZMQ_SNDMORE)
-  if(rc /= 4) stop "davidson_push_results failed to push imax"
+  if(rc /= 4) stop 'davidson_push_results failed to push imax'
 
   rc8 = f77_zmq_send8( zmq_socket_push, v_t(1,imin), 8_8*sz, ZMQ_SNDMORE)
-  if(rc8 /= 8_8*sz) stop "davidson_push_results failed to push vt"
+  if(rc8 /= 8_8*sz) stop 'davidson_push_results failed to push vt'
 
   rc8 = f77_zmq_send8( zmq_socket_push, s_t(1,imin), 8_8*sz, 0)
-  if(rc8 /= 8_8*sz) stop "davidson_push_results failed to push st"
+  if(rc8 /= 8_8*sz) stop 'davidson_push_results failed to push st'
 
 ! Activate is zmq_socket_push is a REQ
 IRP_IF ZMQ_PUSH
 IRP_ELSE
-  integer :: idummy
-  rc = f77_zmq_recv( zmq_socket_push, idummy, 4, 0)
-  if (rc /= 4) then
-    print *, irp_here, ': f77_zmq_send( zmq_socket_push, idummy, 4, 0)'
-    stop 'error'
+  character*(2) :: ok
+  rc = f77_zmq_recv( zmq_socket_push, ok, 2, 0)
+  if ((rc /= 2).and.(ok(1:2)/='ok')) then
+    print *, irp_here, ': f77_zmq_recv( zmq_socket_push, ok, 2, 0)'
+    stop -1
   endif
 IRP_ENDIF
 
@@ -202,29 +202,29 @@ subroutine davidson_pull_results(zmq_socket_pull, v_t, s_t, imin, imax, task_id)
   integer*8                          :: rc8
 
   rc = f77_zmq_recv( zmq_socket_pull, task_id, 4, 0)
-  if(rc /= 4) stop "davidson_pull_results failed to pull task_id"
+  if(rc /= 4) stop 'davidson_pull_results failed to pull task_id'
 
   rc = f77_zmq_recv( zmq_socket_pull, imin, 4, 0)
-  if(rc /= 4) stop "davidson_pull_results failed to pull imin"
+  if(rc /= 4) stop 'davidson_pull_results failed to pull imin'
 
   rc = f77_zmq_recv( zmq_socket_pull, imax, 4, 0)
-  if(rc /= 4) stop "davidson_pull_results failed to pull imax"
+  if(rc /= 4) stop 'davidson_pull_results failed to pull imax'
 
   sz = (imax-imin+1)*N_states_diag
 
   rc8 = f77_zmq_recv8( zmq_socket_pull, v_t(1,imin), 8_8*sz, 0)
-  if(rc8 /= 8*sz) stop "davidson_pull_results failed to pull v_t"
+  if(rc8 /= 8*sz) stop 'davidson_pull_results failed to pull v_t'
 
   rc8 = f77_zmq_recv8( zmq_socket_pull, s_t(1,imin), 8_8*sz, 0)
-  if(rc8 /= 8*sz) stop "davidson_pull_results failed to pull s_t"
+  if(rc8 /= 8*sz) stop 'davidson_pull_results failed to pull s_t'
 
 ! Activate if zmq_socket_pull is a REP
 IRP_IF ZMQ_PUSH
 IRP_ELSE
-  rc = f77_zmq_send( zmq_socket_pull, 0, 4, 0)
-  if (rc /= 4) then
+  rc = f77_zmq_send( zmq_socket_pull, 'ok', 2, 0)
+  if (rc /= 2) then
     print *,  irp_here, ' : f77_zmq_send (zmq_socket_pull,...'
-    stop 'error'
+    stop -1
   endif
 IRP_ENDIF