*** empty log message ***

git-svn-id: http://svn.einsteintoolkit.org/cactus/EinsteinAnalysis/AHFinderDirect/trunk@874 f88db872-0e4f-0410-b76b-b9085cfa78c5

1 files changed, 27 insertions, 14 deletions

diff --git a/param.ccl b/param.ccl
index 5ff9cd6..c555b6b 100644
--- a/param.ccl
+++ b/param.ccl
@@ -455,42 +455,55 @@ keyword patch_system_type "what type of patch system should we use?"
 # ... 1 if FINITE_DIFF_ORDER is set to 2 in "src/include/config.hh"
 # The code checks for this being too small, and reports a fatal error if so.
 #
-int N_ghost_points "number of ghost zones on each side of a patch"
+int ghost_zone_width "number of ghost zones on each side of a patch"
 {
 0:* :: "any integer >= 0"
 } 2
 
-int N_overlap_points \
+#
+# Our code that computes surface integrals over patches (used for
+# computing BH diagnostics like centroids, areas, masses, etc) silently
+# assumes that this parameter is == 1, so you should probably leave
+# it at that setting.
+#
+int patch_overlap_width \
   "number of grid points that nominally-just-touching patches should overlap"
 {
 1:*:2 :: "any integer >= 0; current implementation requires that it be odd"
 } 1
 
 #
+# This parameter sets the angular resolution of all the patch systems:
+# the angular grid spacing in degrees is 90.0/N_zones_per_right_angle.
+#
 # In practice the error in the horizon position is usually dominated
 # by the errors from interpolating the Cactus gij and Kij to the horizon
 # position, not by the angular finite differencing or interpatch interpolation
-# errors.  Thus this parameter can be made quite large (low resolution)
+# errors.  Thus this parameter can be made fairly small (low resolution)
 # for better performance, without seriously affecting the accuracy
 # with which we can locate the horizon.
 #
-# This spacing must integrally divide 90 degrees for full sphere patch
-# systems, or 45 degrees for other patch systems.
+# For any patch system type other than "full sphere", there are patches
+# with 45 degree widths, so this parameter must be even.
 #
-# Also, the computation of surface integrals over the horizon (for horizon
-# areas, masses, and centroids) is most accurate if the number of angular
-# grid zones (i.e. the patch size divided by this parameter) is even or
-# >= 7 (or both) for both coordinates of all patches.
+# Normally we use Simpson's rule (in a variant which doesn't require the
+# number of zones to be even) for angular integrations over the patch
+# system.  However, if the number of angular zones in a patch is very
+# small and odd (i.e. 3 or 5), then we have to use the trapezoid rule
+# instead, so the integrations are less accurate.  This occurs for
+# N_zones_per_right_angle = 3 or 5 for a full sphere patch system,
+# or N_zones_per_right_angle = 6 or 10 for any other patch system type.
 #
-# If you are thinking of setting this to a small value (high resolution),
+# If you are thinking of setting this to a large value (high resolution),
 # note also that with the current dense-matrix storage of the Jacobian,
 # the memory/running time of the LAPACK linear system solve scales as
-# the inverse 4th/6th power of this parameter!
+# the 4th/6th power of this parameter!  For example, doubling the resolution
+# takes 16 times as much memory, and 64 times as long to run!
 #
-real delta_drho_dsigma "angular grid spacing of patches, in degrees"
+int N_zones_per_right_angle "sets angular resolution of patch systems"
 {
-(0.0:* :: "any real number > 0.0"
-} 7.5
+1:* :: "any integer >= 1; must be even for patch systems other than full-sphere"
+} 12
 
 ################################################################################