# HG changeset patch
# User Matthew Turk <matthewturk@gmail.com>
# Date 1283411265 25200
# Branch yt
# Node ID d9bdb37f8046d00d41ea506c0b960782e80121d8
# Parent  e2b55f386569be8b3cf398dcbd19ce1875fa46b9
Cache particle indices, which speeds things up a surprising amount...

diff -r e2b55f386569be8b3cf398dcbd19ce1875fa46b9 -r d9bdb37f8046d00d41ea506c0b960782e80121d8 yt/frontends/flash/data_structures.py
--- a/yt/frontends/flash/data_structures.py	Wed Sep 01 23:34:38 2010 -0700
+++ b/yt/frontends/flash/data_structures.py	Thu Sep 02 00:07:45 2010 -0700
@@ -115,6 +115,8 @@
                               for ax in 'xyz']
         self.grid_dimensions[:] *= (nxb, nyb, nzb)
         self.grid_particle_count[:] = f["/localnp"][:][:,None]
+        self._particle_indices = na.zeros(self.num_grids + 1, dtype='int64')
+        na.add.accumulate(self.grid_particle_count, out=self._particle_indices[1:])
         # 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 e2b55f386569be8b3cf398dcbd19ce1875fa46b9 -r d9bdb37f8046d00d41ea506c0b960782e80121d8 yt/frontends/flash/io.py
--- a/yt/frontends/flash/io.py	Wed Sep 01 23:34:38 2010 -0700
+++ b/yt/frontends/flash/io.py	Thu Sep 02 00:07:45 2010 -0700
@@ -69,8 +69,8 @@
         f = self._handle
         if field in self._particle_fields:
             if grid.NumberOfParticles == 0: return na.array([], dtype='float64')
-            start = na.sum(self.pf.h.grid_particle_count[:grid.id-grid._id_offset])
-            end = start + grid.NumberOfParticles
+            start = self.pf.h._particle_indices[grid.id - grid._id_offset]
+            end = self.pf.h._particle_indices[grid.id - grid._id_offset + 1]
             fi = self._particle_fields[field]
             tr = f["/tracer particles"][start:end, fi]
         else: