On Wed, 31 Mar 2010 23:58:45 +0200, WanMil <wmgcnfg@web.de> writes:
Am 31.03.2010 22:10, schrieb Scott A Crosby:
On Wed, 31 Mar 2010 21:13:49 +0200, WanMil<wmgcnfg@web.de> writes:
my patch interned all keys and additionally the values of a limited number of keys. Maybe it's not necessary to limit the interning of values. So I have attached the very simple but hopefully very effective patch regarding the memory footprint of mkgmap.
My opinion is that its simpler and more robust to intern or pseudointern every tag value. The bad tile had a lot of duplicate values, what if those tags were not on your list of the 'only intern value strings for some keys'?
Regarding your patch: I don't understand the function of the FuzzyIntern class. You build a HashMap from (uninterned) Strings to the interned String. Then you are looking up new strings in this HashMap and use the interned variant. Where's the difference to the (hopefully) very performance optimized intern() method?
Note that this code is not actually interning any strings in with String.intern(). Call it psuedointerning. The purpose of FuzzyIntern was when I believed that String.intern() interned forever, which I considered very undesirable. I wanted semantics that would remove (most) duplicate strings in memory without forcing those strings to remain in RAM forever.
String intern does not intern forever
I didn't know that. Do you have any link where this is specified?
A google search 'java intern weak reference' seems to indicate that Java since version 1.2 uses a weak reference table for string intern, which means that they can be removed. That search offers alternative implementation ideas, such as using a real weak reference hashtable. Scott