# HG changeset patch
# User Jaroslav Hajek <highegg@gmail.com>
# Date 1270638025 -7200
# Node ID e52f41fd82c74b8c81faaef91be73662c443ba86
# Parent  2f8bacc2a57d78ae343fa045cb7254ee8a9818b7
optimize (:) indexing of sparse column vectors

diff --git a/liboctave/ChangeLog b/liboctave/ChangeLog
--- a/liboctave/ChangeLog
+++ b/liboctave/ChangeLog
@@ -1,3 +1,8 @@
+2010-04-07  Jaroslav Hajek  <highegg@gmail.com>
+
+	* Sparse.cc (Sparse<T>::index (const idx_vector&, bool)): Use shallow
+	copy when column is indexed by colon.
+
 2010-04-07  Jaroslav Hajek  <highegg@gmail.com>
 
 	* Sparse.cc (lblookup): Move in front of Sparse<T>::delete_elements.
diff --git a/liboctave/Sparse.cc b/liboctave/Sparse.cc
--- a/liboctave/Sparse.cc
+++ b/liboctave/Sparse.cc
@@ -1472,20 +1472,25 @@
       ("cannot index sparse matrix with an N-D Array");
   else if (idx.is_colon ())
     {
-      // Fast magic colon processing.
-      retval = Sparse<T> (nel, 1, nz);
-
-      for (octave_idx_type i = 0; i < nc; i++)
+      if (nc == 1)
+        retval = *this;
+      else
         {
-          for (octave_idx_type j = cidx(i); j < cidx(i+1); j++)
+          // Fast magic colon processing.
+          retval = Sparse<T> (nel, 1, nz);
+
+          for (octave_idx_type i = 0; i < nc; i++)
             {
-              retval.xdata(j) = data(j); 
-              retval.xridx(j) = ridx(j) + i * nr;
+              for (octave_idx_type j = cidx(i); j < cidx(i+1); j++)
+                {
+                  retval.xdata(j) = data(j); 
+                  retval.xridx(j) = ridx(j) + i * nr;
+                }
             }
+
+          retval.xcidx(0) = 0;
+          retval.xcidx(1) = nz;
         }
-
-      retval.xcidx(0) = 0;
-      retval.xcidx(1) = nz;
     }
   else if (idx.extent (nel) > nel)
     {