[Tm4j-commits] tm4j/src/org/tm4j/topicmap/tmdm/merged MergedAssociationKey.java, 1.2, 1.3

[Xuan B. <med...@us...>]

Update of /cvsroot/tm4j/tm4j/src/org/tm4j/topicmap/tmdm/merged
In directory sc8-pr-cvs10.sourceforge.net:/tmp/cvs-serv16378/src/org/tm4j/topicmap/tmdm/merged

Modified Files:
	MergedAssociationKey.java 
Log Message:
Memory consumption analysis for MergedAssociationKeys.

Index: MergedAssociationKey.java
===================================================================
RCS file: /cvsroot/tm4j/tm4j/src/org/tm4j/topicmap/tmdm/merged/MergedAssociationKey.java,v
retrieving revision 1.2
retrieving revision 1.3
diff -C2 -d -r1.2 -r1.3
*** MergedAssociationKey.java	19 Jun 2008 11:25:11 -0000	1.2
--- MergedAssociationKey.java	21 Jun 2008 16:26:04 -0000	1.3
***************
*** 23,33 ****
  		
  		This object consumes on 64-bit machines, on average,
! 		(2*8+8+8+8+8)+	(MergedAssociationKey:		object header + 1 inherited pointer + 2 pointers + 1 int + alignment)
! 		(2*8+8)+			(HashSet:										object header + 1 pointer)
! 		(2*8+6*8)+		(HashMap: 									object header + content)
! 		(3*8+16*8)+		(HashMap.table:							object header + content (default table size))
! 		(2*8+4*8)*2+	(HashMap.Entry:							object header + content) 2 times (because, typically, associations have 2 roles)
! 		(2*8+8+8)*2		(MergedAssociationRoleKey:	object header + type + player) 2 times (because, typically, associations have 2 roles)
  	= 448 bytes.
  	*/
  	protected MergedTopic													type;
--- 23,50 ----
  		
  		This object consumes on 64-bit machines, on average,
! 		(2*8+8+8+8+8)+	(MergedAssociationKey:			object header + 1 inherited pointer + 2 pointers + 1 int + alignment)
! 		(2*8+8)+				(HashSet:										object header + 1 pointer)
! 		(2*8+6*8)+			(HashMap: 									object header + content)
! 		(3*8+16*8)+			(HashMap.table:							object header + content (default table size))
! 		(2*8+4*8)*2+		(HashMap.Entry:							object header + content) 2 times (because, typically, associations have 2 roles)
! 		(2*8+8+8)*2			(MergedAssociationRoleKey:	object header + type + player) 2 times (because, typically, associations have 2 roles)
  	= 448 bytes.
+ 	
+ 		We should consider an optimization:
+ 		
+ 		(2*8+8+8+8+8)+	(MergedAssociationKey:			object header + 1 inherited pointer + 2 pointers + 1 int + alignment)
+ 		(3*8+2*8*n)			(compressed roles array:		object header + array consisting of pointer to role,player,role,player,role,player,...	) n times (for n roles)
+ 	= 72+16*n bytes.  (=104 bytes for a binary association).
+ 	
+ 		Maybe we should even specialize the association key for binary and ternary associations (because these are the most common ones):
+ 		
+ 		(2*8+8+8+8+8+2*16)	(MergedBinaryAssociationKey:	object header + 1 inherited pointer + 2 pointers + 1 int + alignment + role,player,role,player)
+ 	= 80 bytes (a memory saving of factor 5.6)
+ 	
+ 		(2*8+8+8+8+8+3*16)	(MergedTernaryAssociationKey:	object header + 1 inherited pointer + 2 pointers + 1 int + alignment + role,player,role,player,role,player)
+ 	= 96 bytes (a memory saving of factor 4.6)
+ 	
+ 		At this stage, we should even evaluate whether cacheing the hashCode makes sense, as the hashCode is already cached in java.util.HashMap$Entry.
+ 		If we kill the hashCode, we improve by another 8 bytes (because we do not need alignment anymore), saving another 10% for MergedBinaryAssociationKey. 
  	*/
  	protected MergedTopic													type;