From 443cf93825ef8ce18ececf855478684234b7cb2f Mon Sep 17 00:00:00 2001
From: Richard Hattersley <rhattersley@gmail.com>
Date: Thu, 22 Nov 2012 15:00:45 +0000
Subject: [PATCH 1/3] Faster masked array creation in DataManager.

---
 lib/iris/fileformats/manager.py | 13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)

diff --git a/lib/iris/fileformats/manager.py b/lib/iris/fileformats/manager.py
index d9bd1dfb2e..3aa3c44b05 100644
--- a/lib/iris/fileformats/manager.py
+++ b/lib/iris/fileformats/manager.py
@@ -249,13 +249,16 @@ def load(self, proxy_array):
         
         # Create fully masked data (all missing)
         try:
-            data = numpy.ma.zeros(array_shape, dtype=self.data_type.newbyteorder('='), fill_value=self.mdi)
-            data.mask = True
+            raw_data = numpy.empty(array_shape,
+                                   dtype=self.data_type.newbyteorder('='))
+            mask = numpy.ones(array_shape, dtype=numpy.bool)
+            data = numpy.ma.MaskedArray(raw_data, mask=mask,
+                                        fill_value=self.mdi)
         except ValueError:
             raise DataManager.ArrayTooBigForAddressSpace(
-                             'Cannot create an array of shape %r as it will not fit in memory. Try reducing the shape '
-                             'of the proxy array by using indexing.' % (array_shape, )
-                             )
+                    'Cannot create an array of shape %r as it will not'
+                    ' fit in memory. Try reducing the shape of the'
+                    ' proxy array by using indexing.'.format(array_shape))
 
         for index, proxy in numpy.ndenumerate(proxy_array):
             if proxy not in [None, 0]:  # 0 can come from slicing masked proxy; numpy.array(masked_constant).

From fb093b29c3b4d2136ad37e3698661cad56401fec Mon Sep 17 00:00:00 2001
From: Richard Hattersley <rhattersley@gmail.com>
Date: Fri, 23 Nov 2012 12:22:23 +0000
Subject: [PATCH 2/3] Faster masked array creation in merge

---
 lib/iris/_merge.py | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/lib/iris/_merge.py b/lib/iris/_merge.py
index c6d67c1b78..fa68768cf1 100644
--- a/lib/iris/_merge.py
+++ b/lib/iris/_merge.py
@@ -1144,13 +1144,14 @@ def _get_cube(self):
         # Create fully masked data i.e. all missing.
         if signature.data_manager is None:
             # Must zero the data in order to avoid random checksums.
-            data = numpy.ma.zeros(self._shape, dtype=signature.data_type)
-            data.fill_value = signature.mdi
+            data = numpy.ma.MaskedArray(numpy.zeros(self._shape,
+                                                    signature.data_type),
+                                        mask=numpy.ones(self._shape, 'bool'),
+                                        fill_value=signature.mdi)
         else:
-            # With dtype=object, ma.empty DOES initialise the memory (all None).
-            data = numpy.ma.empty(self._shape, dtype=object)
+            data = numpy.ma.MaskedArray(numpy.zeros(self._shape, 'object'),
+                                        mask=numpy.ones(self._shape, 'bool'))
 
-        data.mask = True
         cube = iris.cube.Cube(data,
                               dim_coords_and_dims=dim_coords_and_dims,
                               aux_coords_and_dims=aux_coords_and_dims,

From f4bdfb48fbbfe27e68264e3d9a74e18016c45cc8 Mon Sep 17 00:00:00 2001
From: Richard Hattersley <rhattersley@gmail.com>
Date: Tue, 27 Nov 2012 16:05:04 +0000
Subject: [PATCH 3/3] Tweak comment and error text

---
 lib/iris/_merge.py              | 5 +++--
 lib/iris/fileformats/manager.py | 6 +++---
 2 files changed, 6 insertions(+), 5 deletions(-)

diff --git a/lib/iris/_merge.py b/lib/iris/_merge.py
index fa68768cf1..ef11235d93 100644
--- a/lib/iris/_merge.py
+++ b/lib/iris/_merge.py
@@ -1141,9 +1141,10 @@ def _get_cube(self):
         aux_coords_and_dims = [(deepcopy(coord), dims) for coord, dims in self._aux_coords_and_dims]
         kwargs = dict(zip(iris.cube.CubeMetadata._fields, signature.defn))
 
-        # Create fully masked data i.e. all missing.
+        # Create fully masked data, i.e. all missing.
+        # (The CubeML checksum doesn't respect the mask, so we zero the
+        # underlying data to ensure repeatable checksums.)
         if signature.data_manager is None:
-            # Must zero the data in order to avoid random checksums.
             data = numpy.ma.MaskedArray(numpy.zeros(self._shape,
                                                     signature.data_type),
                                         mask=numpy.ones(self._shape, 'bool'),
diff --git a/lib/iris/fileformats/manager.py b/lib/iris/fileformats/manager.py
index 3aa3c44b05..0a906cf9d9 100644
--- a/lib/iris/fileformats/manager.py
+++ b/lib/iris/fileformats/manager.py
@@ -256,9 +256,9 @@ def load(self, proxy_array):
                                         fill_value=self.mdi)
         except ValueError:
             raise DataManager.ArrayTooBigForAddressSpace(
-                    'Cannot create an array of shape %r as it will not'
-                    ' fit in memory. Try reducing the shape of the'
-                    ' proxy array by using indexing.'.format(array_shape))
+                    'Cannot create an array of shape %r as it will not fit in'
+                    ' memory. Consider using indexing to select a subset of'
+                    ' the Cube.'.format(array_shape))
 
         for index, proxy in numpy.ndenumerate(proxy_array):
             if proxy not in [None, 0]:  # 0 can come from slicing masked proxy; numpy.array(masked_constant).