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;
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