CarpetRegrid2: Combine all components into a single one if that is efficient

Introduce a parameter "min_fraction" that defines, indirectly, how
many additional refined grid points can be introduced if that leads to
a simpler structure.

If using a single refined region instead of several ones would not
introduce too many unnecessarily refined grid points, then do so.

darcs-hash:20061205175426-dae7b-18d2467cf123b734aaef19eb2f5f9c4994480b99.gz

2 files changed, 31 insertions, 0 deletions

diff --git a/Carpet/CarpetRegrid2/param.ccl b/Carpet/CarpetRegrid2/param.ccl
index 41414eda2..df17204dd 100644
--- a/Carpet/CarpetRegrid2/param.ccl
+++ b/Carpet/CarpetRegrid2/param.ccl
@@ -20,6 +20,13 @@ CCTK_INT min_distance "Minimum distance (in grid points) between coarse and fine
 
 
 
+CCTK_REAL min_fraction "Minimum fraction of required refined points that need to be present in a refined region"
+{
+  0:* :: ""
+} 0.9
+
+
+
 CCTK_INT regrid_every "Regrid every n time steps" STEERABLE=always
 {
   -1   :: "regrid never"
diff --git a/Carpet/CarpetRegrid2/src/regrid.cc b/Carpet/CarpetRegrid2/src/regrid.cc
index 32a590d54..5f581d3b6 100644
--- a/Carpet/CarpetRegrid2/src/regrid.cc
+++ b/Carpet/CarpetRegrid2/src/regrid.cc
@@ -448,6 +448,30 @@ namespace CarpetRegrid2 {
       // Simplify the set of refined regions
       regions.at(rl).normalize();
       
+      // Check whether it would be worthwhile to combine the regions
+      // into a single region
+      {
+        ibbox single;
+        for (ibboxset::const_iterator ibb = regions.at(rl).begin();
+             ibb != regions.at(rl).end();
+             ++ ibb)
+        {
+          ibbox bb = * ibb;
+          single = single.expanded_containing (bb);
+        }
+        
+        CCTK_REAL const regions_size
+          = static_cast <CCTK_REAL> (regions.at(rl).size());
+        CCTK_REAL const single_size
+          = static_cast <CCTK_REAL> (single.size());
+        
+        // Would a single bbox be efficient enough?
+        if (regions_size >= min_fraction * single_size) {
+          // Combine the boxes
+          regions.at(rl) = ibboxset (single);
+        }
+      }
+      
       // Create a vector of bboxes for this level
       gh::cexts bbs;
       gh::cbnds obs;