********> update.14

Authors: Vinicius Wilian D. Cruzeiro

Date: May 21, 2018

Programs: pmemd

Description: Adds an error message when users run REMD and the box sizes are not the same across all replicas.

--------------------------------------------------------------------------------

 src/pmemd/src/master_setup.F90 | 44 ++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 44 insertions(+)

diff --git src/pmemd/src/master_setup.F90 src/pmemd/src/master_setup.F90
index 440ce62..5ecfe73 100644
--- src/pmemd/src/master_setup.F90
+++ src/pmemd/src/master_setup.F90
@@ -96,6 +96,12 @@ subroutine master_setup(num_ints, num_reals, new_stack_limit, terminal_flag)
   character(8)          :: date
   character(10)         :: time
   character(512)        :: char_tmp_512
+  
+#ifdef MPI
+  double precision      :: val
+  double precision, allocatable :: repvals(:)
+  integer               :: alloc_failed
+#endif
 
   inerr = 0
 
@@ -461,6 +467,44 @@ subroutine master_setup(num_ints, num_reals, new_stack_limit, terminal_flag)
 
   if (using_pme_potential) &
     call print_mdin_ewald_dat(box_alpha, box_beta, box_gamma, box, es_cutoff)
+    
+#ifdef MPI
+  ! Prints an error if REMD is to be performed with different cell sizes across
+  ! the different replicas
+  if (remd_method .ne. 0 .and. ntp .eq. 0) then
+    allocate(repvals(numgroups), stat = alloc_failed)
+    if (alloc_failed .ne. 0) then
+      write(mdout, '(a,a)') error_hdr, 'Error in master_setup'
+      write(mdout, '(a,a)') extra_line_hdr, 'allocation error'
+      call mexit(6,1)
+    end if
+    do i = 1, 6
+       repvals(:) = 0.d0
+       if (i .lt. 4) then
+         val = box(i)
+       else if (i .eq. 4) then
+         val = box_alpha
+       else if (i .eq. 5) then
+         val = box_beta
+       else if (i .eq. 6) then
+         val = box_gamma
+       end if
+       call mpi_allgather(val, 1, mpi_double_precision, &
+                          repvals, 1, mpi_double_precision, &
+                          pmemd_master_comm, err_code_mpi)
+       do j = 2, numgroups
+         if (abs(repvals(j)-repvals(1)) .gt. 1.0d-5) then
+           write(mdout,'(a,a,a)') error_hdr, "The box sizes do not match for all REMD replicas."
+           write(mdout,'(11x,a)') "This can happen, for example, if you are using different input coordinate files"
+           write(mdout,'(11x,a)') "for the different replicas and these structures come from a NPT run."
+           write(mdout,'(11x,a)') "Make sure the box lengths and angles are the same for all replicas in all input"
+           write(mdout,'(11x,a)') "coordinate files."
+           call mexit(6,1)
+         end if
+       end do
+    end do
+  end if
+#endif /* MPI */
 
 ! Check if ifbox variable from prmtop file matches actual angles.  This must
 ! occur immediately after print_mdin_ewald_dat for consistency with sander11