Added in xh2xb coordinate transform method

src/modules/swiftest_classes.f90

@@ -226,6 +226,7 @@ module swiftest_classes
       procedure :: append       => util_append_pl         !! Appends elements from one structure to another
       procedure :: h2b          => util_coord_h2b_pl      !! Convert massive bodies from heliocentric to barycentric coordinates (position and velocity)
       procedure :: b2h          => util_coord_b2h_pl      !! Convert massive bodies from barycentric to heliocentric coordinates (position and velocity)
+      procedure :: xh2xb        => util_coord_xh2xb_pl    !! Convert position vectors of massive bodies from heliocentric to barycentric coordinates (position and velocity)
       procedure :: fill         => util_fill_pl           !! "Fills" bodies from one object into another depending on the results of a mask (uses the UNPACK intrinsic)
       procedure :: resize       => util_resize_pl         !! Checks the current size of a Swiftest body against the requested size and resizes it if it is too small.
       procedure :: set_beg_end  => util_set_beg_end_pl    !! Sets the beginning and ending positions and velocities of planets.
@@ -936,6 +937,12 @@ module subroutine util_coord_h2b_tp(self, cb)
          class(swiftest_cb), intent(in)    :: cb   !! Swiftest central body object
       end subroutine util_coord_h2b_tp
 
+      module subroutine util_coord_xh2xb_pl(self, cb)
+         implicit none
+         class(swiftest_pl), intent(inout) :: self !! Swiftest massive body object
+         class(swiftest_cb), intent(inout) :: cb   !! Swiftest central body object
+      end subroutine util_coord_xh2xb_pl
+
       module subroutine util_copy_encounter(self, source)
          implicit none
          class(swiftest_encounter), intent(inout) :: self   !! Encounter list 

src/symba/symba_collision.f90

@@ -1076,7 +1076,7 @@ module subroutine symba_collision_resolve_plplenc(self, system, param, t)
 
                write(*, *) "Collision between massive bodies detected at time t = ", t
                call pl%vb2vh(system%cb)
-               call pl%h2b(system%cb)
+               call pl%xh2xb(system%cb)
                if (param%lfragmentation) then
                   call plplcollision_list%resolve_fragmentations(system, param)
                else

src/util/util_coord.f90

@@ -42,6 +42,42 @@ module subroutine util_coord_h2b_pl(self, cb)
    end subroutine util_coord_h2b_pl
 
 
+   module subroutine util_coord_xh2xb_pl(self, cb)
+      !! author: David A. Minton
+      !!
+      !! Convert position vectors of massive bodies from heliocentric to barycentric coordinates (position and velocity)
+      !!
+      !! Adapted from David E. Kaufmann's Swifter routine coord_h2b.f90 
+      !! Adapted from Hal Levison's Swift routine coord_h2b.f 
+      implicit none
+      ! Arguments
+      class(swiftest_pl), intent(inout) :: self !! Swiftest massive body object
+      class(swiftest_cb), intent(inout) :: cb   !! Swiftest central body object
+      ! Internals
+      integer(I4B)  :: i
+      real(DP)      :: Gmtot
+      real(DP), dimension(NDIM) :: xtmp
+
+      if (self%nbody == 0) return
+      associate(pl => self, npl => self%nbody)
+         Gmtot = cb%Gmass
+         xtmp(:) = 0.0_DP
+         do i = 1, npl
+            if (pl%status(i) == INACTIVE) cycle
+            Gmtot = Gmtot + pl%Gmass(i)
+            xtmp(:) = xtmp(:) + pl%Gmass(i) * pl%xh(:,i)
+         end do
+         cb%xb(:) = -xtmp(:) / Gmtot
+         do i = 1, npl
+            if (pl%status(i) == INACTIVE) cycle
+            pl%xb(:,i) = pl%xh(:,i) + cb%xb(:)
+         end do
+      end associate
+
+      return
+   end subroutine util_coord_xh2xb_pl
+
+
    module subroutine util_coord_h2b_tp(self, cb)
       !! author: David A. Minton
       !!