update comments in compute_synchronize_Jacobian() and synchronize_Jacobian()

git-svn-id: http://svn.einsteintoolkit.org/cactus/EinsteinAnalysis/AHFinderDirect/trunk@689 f88db872-0e4f-0410-b76b-b9085cfa78c5

1 files changed, 29 insertions, 30 deletions

diff --git a/src/patch/patch_system.cc b/src/patch/patch_system.cc
index 2138732..f4881e9 100644
--- a/src/patch/patch_system.cc
+++ b/src/patch/patch_system.cc
@@ -1403,33 +1403,10 @@ void patch_system::synchronize(int ghosted_min_gfn_to_sync,
 //******************************************************************************
 
 //
-// This function computes the Jacobian of  synchronize()  into internal
-// buffers, taking into account synchronize()'s full 3-phase algorithm.
-// There are several cases:
-// - ghost zone is symmetry && x point is in non-corner
-//   --> x value was computed by a phase 1 symmetry operation,
-//       from nominal-grid data
-//   ==> use the ghost zone's Jacobian unchanged
-// - ghost zone is symmetry && x point is in corner
-//   --> x value was computed by a phase 3 symmetry operation,
-//       - from a symmetry ghost zone,
-//         which must have been computed in phase 1 from nominal-grid data
-//         ==> use the two symmetry ghost zones' combined Jacobian
-//       - from an interpatch ghost zone
-//         ==> use that interpatch ghost zone's Jacobian
-// - ghost zone is interpatch
-//   --> x value was computed by a phase 2 interpatch interpolation
-//       - from (only) nominal-grid data
-//         ==> use that interpatch ghost zone's Jacobian unchanged
-//       - from a mixture of nominal-grid data
-//         and data computed by a phase 1 symmetry operation
-//         ==> "fold" the interpatch ghost zone's Jacobian
-//             to reflect the phase 1 symmetry operation
-//
-// It also properly sets  global_{min,max}_ym_ .
-//
-// FIXME FIXME: at the moment we ignore the 3-phase algorithm and just
-//		pass all the Jacobian operations down to the ghost zones
+// This function does any precomputation necessary to compute the Jacobian
+// of  synchronize() , taking into account synchronize()'s full 3-phase
+// algorithm.  In practice, this means it computes the individual Jacobian
+// of each ghost zone, and sets  global_{min,max}_ym_ .
 //
 void patch_system::compute_synchronize_Jacobian(int ghosted_min_gfn_to_sync,
 						int ghosted_max_gfn_to_sync)
@@ -1491,9 +1468,6 @@ max_ym = global_max_ym_;
 //	Jacobian_buffer(ym)
 //   for each  ym  in the min/max ym range
 //
-// FIXME FIXME: at the moment we ignore the 3-phase algorithm and just
-//		pass all the operation down to the ghost zones
-//
 const patch_edge&
   patch_system::synchronize_Jacobian(const ghost_zone& xgz,
 				     int x_iperp, int x_ipar,
@@ -1502,6 +1476,31 @@ const patch_edge&
 				     jtutil::array1d<fp>& Jacobian_buffer)
 	const
 {
+//
+// Implementation notes:
+//
+// There are several cases for the 3-phase algorithm.
+// - ghost zone is symmetry && x point is in non-corner
+//   --> x value was computed by a phase 1 symmetry operation,
+//       from nominal-grid data
+//   ==> use the ghost zone's Jacobian unchanged
+// - ghost zone is symmetry && x point is in corner
+//   --> x value was computed by a phase 3 symmetry operation,
+//       - from a symmetry ghost zone,
+//         which must have been computed in phase 1 from nominal-grid data
+//         ==> use the two symmetry ghost zones' combined Jacobian
+//       - from an interpatch ghost zone
+//         ==> use that interpatch ghost zone's Jacobian
+// - ghost zone is interpatch
+//   --> x value was computed by a phase 2 interpatch interpolation
+//       - from (only) nominal-grid data
+//         ==> use that interpatch ghost zone's Jacobian unchanged
+//       - from a mixture of nominal-grid data
+//         and data computed by a phase 1 symmetry operation
+//         ==> "fold" the interpatch ghost zone's Jacobian
+//             to reflect the phase 1 symmetry operation
+//
+
 y_iperp = xgz.Jacobian_y_iperp(x_iperp);
 
 y_posn = xgz.Jacobian_y_ipar_posn(x_iperp, x_ipar);