comp.lang.java.programmer Google Group

Re: The future of Java

2009-11-25T01:42:57Z

On Sun, 22 Nov 2009 21:56:54 -0500, Arne Vajhøj <a...@vajhoej.dk>
wrote, quoted or indirectly quoted someone who said :
I have seen vendors wriggle out of these sorts of promise by creating
a new product and just letting the old one languish. The wording of
the GPL licence may make that difficult for Sun and Oracle. Does the

Re: The future of Java

2009-11-25T01:23:00Z

On Sun, 22 Nov 2009 22:05:05 -0500, Arne Vajhøj <a...@vajhoej.dk>
wrote, quoted or indirectly quoted someone who said :
Under heavy loads a system can have can a variety of behaviours:
in increasing desirability
1. the system crashes outright.
2. the throughput drops precipitously. (e.g. virtual ram thrashing).

Re: Hash table performance

2009-11-25T01:04:32Z

I wasn't using bit masking and powers of two, I was using double the
previous table size then add 1, and integer modulo to limit the hash
index to the table size. I even started with a hash table size of 101.
I was using closed hashing however, which did not help.
I was *still* getting a huge clump of collisions right in the middle of

Re: Hash table performance

2009-11-24T23:58:33Z

Ahaaa, yes, of course. Those bits in full:
0.0 000000000000000000000000000000 000000000000000000000000000000 0000
1.0 001111111111000000000000000000 000000000000000000000000000000 0000
2.0 010000000000000000000000000000 000000000000000000000000000000 0000
3.0 010000000000100000000000000000 000000000000000000000000000000 0000

Re: Hash table performance

2009-11-24T23:55:58Z

I suppose that it is mature since they've made it available and I also
suppose that they found out that benefits of EA were not that great
for many classes of programs when compared to longer JITting - but
that's just my thinking.
Semantically yes but in the case of synchronized method there is no
accompanying bytecode instruction, namely monitorenter/monitorexit

Re: Hash table performance

2009-11-25T00:57:55Z

No, it applies to all untagged value types including byte, int, long, float,
double and any user defined value types like complex numbers or vertex
data.
Interestingly, this reminds me of a lecture one of the JVM designers gave,
describing how they felt it was preferable to build a VM upon dynamic
language principles. The JVM's awful performance here is a direct

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2009-11-24T23:18:07Z

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Re: Hash table performance

2009-11-24T23:14:54Z

According to Patricia Shanahan <p...@acm.org>:
Integer division tends to be slow on modern hardware. The Intel
optimization manual which happens to conveniently reside on my harddisk
states that latency for a simple "idiv" opcode is between 56 and 70
clock cycles, while masking uses only a fraction of a clock cycle.

Re: Hash table performance

2009-11-24T22:58:31Z

Given current division speeds, does it really make sense to use a
power-of-two bucket count?
Many years ago, I had to design a hash table for use on a machine with
integer remainder *very* slow compared to masking. I found that I got
slightly more collisions with a power of two size than a prime size, but

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2009-11-24T22:07:56Z

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Re: Hash table performance

2009-11-24T22:06:54Z

Writing my own hash table implementation, I noticed that I was getting
terrible performance with a ton of collisions and everything was heaped
up in a tiny spot in the table.
Inspecting the hash in hexadecimal, I realized that Jon's data keys --
the natural counting numbers 1, 2, 3, etc. -- are represented in a

Re: The future of Java

2009-11-24T22:00:43Z

That's good to know.
However, for my immediate application, table locking is probably not a
problem since during normal processing DB updating is a single threaded
bulk load that can be done overnight and/or in a quiet time. The only
other accesses are read-only apart from occasional bouts of data

Re: Windows 7 and all my Java stuff.

2009-11-24T21:16:42Z

According to Arved Sandstrom <dces...@hotmail.com>:
When I worry about RAM, it is mostly for a few routines where performance
happens to be critical, and there I worry about "fast RAM". Fast RAM is
the RAM which is accessed without any extra delay. On a recent CPU this
means L1 cache. My relatively recent Intel CPU has a 32 kB L1 cache

Re: good porn site

2009-11-24T20:46:54Z

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Re: Windows 7 and all my Java stuff.

2009-11-24T20:44:28Z

[ SNIP ]
I was being somewhat tongue in cheek about the memory thing. :-) I have
to agree, even with application bloat I spend a much smaller fraction of
my time these days worrying about memory than I did 20 or 30 years ago.
Well, to be accurate, I still worry about memory but now it's not RAM
I'm thinking about.