[Python-checkins] python/dist/src/Objects dictnotes.txt,1.4,1.5

[rhettinger at users.sourceforge.net]

Update of /cvsroot/python/python/dist/src/Objects
In directory sc8-pr-cvs1.sourceforge.net:/tmp/cvs-serv30246

Modified Files:
	dictnotes.txt 
Log Message:
Fix typos and add some elaborations

Index: dictnotes.txt
===================================================================
RCS file: /cvsroot/python/python/dist/src/Objects/dictnotes.txt,v
retrieving revision 1.4
retrieving revision 1.5
diff -C2 -d -r1.4 -r1.5
*** dictnotes.txt	28 May 2003 14:10:46 -0000	1.4
--- dictnotes.txt	15 Mar 2004 15:52:22 -0000	1.5
***************
*** 95,99 ****
      Raising this to *4 results in half the number of resizes,
      less effort to resize, better sparseness for some (but not
!     all dict sizes), and potentially double memory consumption
      depending on the size of the dictionary.  Setting to *4
      eliminates every other resize step.
--- 95,99 ----
      Raising this to *4 results in half the number of resizes,
      less effort to resize, better sparseness for some (but not
!     all dict sizes), and potentially doubles memory consumption
      depending on the size of the dictionary.  Setting to *4
      eliminates every other resize step.
***************
*** 113,116 ****
--- 113,118 ----
  non-overlapping memory accesses for keys(), items(), values(),
  __iter__(), iterkeys(), iteritems(), itervalues(), and update().
+ Also, every dictionary iterates at least twice, once for the memset()
+ when it is created and once by dealloc().
  
  
***************
*** 192,195 ****
--- 194,199 ----
     ratio at 5% or 10% instead of the usual 66.7%.  This will sharply
     curtail the number of collisions but will increase iteration time.
+    The builtin namespace is a prime example of a dictionary that can
+    benefit from being highly sparse.
  
  2) Dictionary creation time can be shortened in cases where the ultimate
***************
*** 200,204 ****
     a more sparse environment than before.  The preconditions for this
     strategy arise whenever a dictionary is created from a key or item
!    sequence and the number of unique keys is known.
  
  3) If the key space is large and the access pattern is known to be random,
--- 204,208 ----
     a more sparse environment than before.  The preconditions for this
     strategy arise whenever a dictionary is created from a key or item
!    sequence and the number of *unique* keys is known.
  
  3) If the key space is large and the access pattern is known to be random,
***************
*** 229,237 ****
  jostled (to minimize collisions).  The lookdict() routine can then
  eliminate the test for dummy entries (saving about 1/4 of the time
! spend in the collision resolution loop).
  
  An additional possibility is to insert links into the empty spaces
  so that dictionary iteration can proceed in len(d) steps instead of
! (mp->mask + 1) steps.
  
  
--- 233,242 ----
  jostled (to minimize collisions).  The lookdict() routine can then
  eliminate the test for dummy entries (saving about 1/4 of the time
! spent in the collision resolution loop).
  
  An additional possibility is to insert links into the empty spaces
  so that dictionary iteration can proceed in len(d) steps instead of
! (mp->mask + 1) steps.  Alternatively, a separate tuple of keys can be
! kept just for iteration.