# HG changeset patch
# User Matthew Turk <matthewturk@gmail.com>
# Date 1283408589 25200
# Branch yt
# Node ID ae6149ab12f91c2abc611b51f92ea2948664857c
# Parent  48274493af4e82e80ce2a83c982dee71f88486a8
Assuming sorted particles, the particle IO is now substantially faster in FLASH
datasets.

diff -r 48274493af4e82e80ce2a83c982dee71f88486a8 -r ae6149ab12f91c2abc611b51f92ea2948664857c yt/frontends/flash/data_structures.py
--- a/yt/frontends/flash/data_structures.py	Wed Sep 01 23:13:35 2010 -0700
+++ b/yt/frontends/flash/data_structures.py	Wed Sep 01 23:23:09 2010 -0700
@@ -114,21 +114,7 @@
             nxb, nyb, nzb = [int(f["/simulation parameters"]['n%sb' % ax])
                               for ax in 'xyz']
         self.grid_dimensions[:] *= (nxb, nyb, nzb)
-        # particle_count is harder.  We stride over the particle file and count
-        # up per grid.
-        npart = f["/tracer particles"].shape[0]
-        blki = [s[0].strip() for s in f["/particle names"][:]].index("blk")
-        start = 0
-        stride = 1e6
-        while start < npart:
-            end = min(start + stride - 1, npart)
-            blks = f["/tracer particles"][start:end,blki].astype("int64")
-            ta = na.bincount(blks)
-            old_size = ta.size
-            ta = na.resize(ta, self.num_grids)
-            ta[old_size:] = 0
-            self.grid_particle_count += ta[:,None]
-            start = end
+        self.grid_particle_count[:] = f["/localnp"][:][:,None]
         # This will become redundant, as _prepare_grid will reset it to its
         # current value.  Note that FLASH uses 1-based indexing for refinement
         # levels, but we do not, so we reduce the level by 1.
diff -r 48274493af4e82e80ce2a83c982dee71f88486a8 -r ae6149ab12f91c2abc611b51f92ea2948664857c yt/frontends/flash/io.py
--- a/yt/frontends/flash/io.py	Wed Sep 01 23:13:35 2010 -0700
+++ b/yt/frontends/flash/io.py	Wed Sep 01 23:23:09 2010 -0700
@@ -68,7 +68,10 @@
     def _read_data_set(self, grid, field):
         f = self._handle
         if field in self._particle_fields:
-            tr = self._select_particles(grid, field)
+            start = na.sum(self.pf.h.grid_particle_count[:grid.id-grid._id_offset])
+            end = start + grid.NumberOfParticles
+            fi = self._particle_fields[field]
+            tr = f["/tracer particles"][start:end, fi]
         else:
             tr = f["/%s" % field][grid.id - grid._id_offset,:,:,:].transpose()
         return tr.astype("float64")