Re: Java 7 vs 8 speed issues on Win7?

From:
Knute Johnson <nospam@rabbitbrush.frazmtn.com>
Newsgroups:
comp.lang.java.programmer
Date:
Wed, 05 Nov 2014 20:00:59 -0800
Message-ID:
<m3erpb$qt5$1@dont-email.me>
On 11/5/2014 18:37, Eric Sosman wrote:

On 11/5/2014 8:32 PM, Knute Johnson wrote:

On 11/5/2014 11:47, Jan Burse wrote:

A fundamental change in one of the newer JDKs
is a changed semantics for substring(int, int).


For better or worse?


     "Yes, probably."

     (Given the amount of data provided, that's really all the
answer one can offer -- and all that's deserved. C'mon, Knute:
No description of the application, no hint about its hot spots,
no profiling data, not even *one* measurement of any kind at
all ... How in the world can you expect useful feedback when
you've not fed forward?)


I think we are talking about two different things here.

Unfortunately I can't give any good details because I was working on
this 250 miles away with VNC. The customer had a failed computer and we
had to get it running without any delays.

It is not code that was stretching the previous machine with a single
processor running XP and Java 6 but when we configured a new computer
with a multi-core processor, Win7 and Java 7 the code barely ran. It
was so slow that it was no longer usable. Put in Java 8 and it is back
to its old self, tuning along just fine. I haven't been able to
duplicate it in my shop and we can't stop the customer's computers to
play with them.

As to Jan's comments, there isn't a single call to String.substring() in
the code anywhere and it runs fine with Java 8, so I don't think that is
the cause. But I am still curious about what the "changed semantics"
are and how they might impact performance.

Thanks,

knute...

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