Gary Robinson: >(I could test the particular case I mention, but I'm wondering if someone has >some fundamental knowledge that would lead to a basic understanding.)<
Java is one of the languages most avid of memory, often even more than Python 2.x. Some bad people have said that Java developers were not that interested in saving RAM because Sun sells hardware, and the more RAM it uses the more they can sell ;-) More seriously, Java uses a complex hybrid generational garbage collectors, while CPython uses a much simpler reference count GC + cycle detector. A reference counter usually has a lower performance compared to good generational garbage collectors, especially if they are hybridized with several other algorithms, but it's simpler (and most things in CPython design are designed for simplicity even when they are a little less efficient, and among other things this simplicity helps this OpenSource project recruit and keep developers), it's almost deterministic (so for example in some situations you can forget to close a file) so it often uses less memory because in any moment you have only the objects you are using (reference cycles add a little extra complexity in this). While a generational GC keeps a lot of extra memory unused, free, etc. There are studies that show that if you use such kind of good generational GCs and you pay about a 2-5X memory penalty you can have a language about as fast as ones where you manually manage memory. Indeed today good Java programs are often no more than 2X slower than C++ and sometimes are about as fast or even faster (thanks to other optimizations, like a strong inlining of virtual methods done by HotSpot). If you want a language that uses less RAM you can try FreePascal :-) I think that among the languages designed to work with a GC, the D language is among the ones that uses less memory (because so far its GC is not that good, so it saves memory while being slower than the advanced GC used by Sun Java). On 64 bit systems Java Sun has added an optimization, certain pointers are compressed in 32 bits, reducing memory usage. Similar things may be done by the LLVM too in future: http://llvm.org/pubs/2005-06-12-MSP-PointerCompSlides.pdf Maybe someday 64-bit CPython will do the same, or maybe UnlandenSwallow or PyPy (Jthon in a sense may do it already if you use it on a 64 bit Java. I don't know). Bye, bearophile -- http://mail.python.org/mailman/listinfo/python-list
