Path: csiph.com!usenet.pasdenom.info!news.albasani.net!.POSTED!not-for-mail
From: Jan Burse <janburse@fastmail.fm>
Newsgroups: comp.lang.java.programmer
Subject: Re: Good Fowler article on ORM
Date: Sat, 12 May 2012 12:01:03 +0200
Organization: albasani.net
Lines: 45
Message-ID: <jolcd0$3g7$1@news.albasani.net>
References: <kDXqr.1107$FL3.615@newsfe11.iad> <vokoq7t9vj5cf68rk9ricd63meejh8r3rk@4ax.com> <joihae$oiv$1@news.albasani.net> <jokg12$jce$1@dont-email.me>
Mime-Version: 1.0
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Content-Transfer-Encoding: 7bit
X-Trace: news.albasani.net RKgOjqbzrG5qjIo54N3MRT/zJOGO7iPWT71AP8dBBEgtlH61Aizw2VRjJ4XUuz+vuPYQoLFvD5uvoNVhPtODQxiBpPsxHzHLi+z/JPmI9P0Oge7IF+wcOOgURAlmynEq
NNTP-Posting-Date: Sat, 12 May 2012 10:01:04 +0000 (UTC)
Injection-Info: news.albasani.net; logging-data="iXZyIdyP10dESXKGaMkuqJA/yL/dCWCSMLZvLRfRJVF7nzBFAr55V7X9QeSZrDO//Z7Ordl9T4N8uJsQKUFjCjuURL7e/BQSA5XWL915BIjQrKgn3/GJsduUYPfKVyUl"; mail-complaints-to="abuse@albasani.net"
User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.6; rv:12.0) Gecko/20120429 Firefox/12.0 SeaMonkey/2.9.1
In-Reply-To: <jokg12$jce$1@dont-email.me>
Cancel-Lock: sha1:qc0JDLezeC+wir51TNpCj/w9KYc=
Xref: csiph.com comp.lang.java.programmer:14484

David Lamb schrieb:
> On 11/05/2012 4:06 AM, Jan Burse wrote:
>> I also went for a custom implementation of some of
>> the Collection classes, to have the algorithms not
>> use iterators, but inline loops for speed. Isn't
>> possible with the existing classes since one cannot
>> access the fields.
>
> Isn't that the sort of optimization a JIT compiler
> is supposed to be able to do?

This would be a very very good JIT compiler. Since the
issues is not simply inlining setters/getters.

The issue is that there are at first hand no setter/getters.
For example the table field of a HashMap is private.

And then an iterator implies creating a new stateful object.
Take for example the following trivial iteration without
an iterator over a HashMap:

   for (int i = 0; i<table.length; i++) {
       Entry e = table[i];
       while (e!=null) {
           /* do something */
       }
   }

When doing the above iteration with an iterator, the iterator
must keep i and e as a state, typically on the heap. Without
an iterator i and e can be registers.

Maybe some JITs are able to eliminate the heap allocation,
there is a further issues. The above loop does not do
modification checks. Which is valid in my application scenario.

So this is the second reason to inline the loops manually
for speed, less functionality is needed.

Of course one looses encapsulation of iterators. So it only
works a for a particular implementation of a HashMap, and
polymorphism is not anymore supported.

Bye