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multi-core CPU and multithreading

 
 
Lew
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      01-18-2008
Andreas Leitgeb wrote:
> Lew <(E-Mail Removed)> wrote:
>> Often people will say, "That's the platform I'm stuck with." This begs the
>> question of why one is stuck with the platform. What are the reasons?

>
> Ever so often the reason is: "Never change a running system"


That doesn't apply in this case, since the question was sparked by someone
needing to write new code.

It's a good principle, except for the part about never changing a running system.

The problem is that running systems frequently are not error free, and further
often do not adapt well to changing needs or circumstances.

>> Conversion costs are next to zero. Risk is also near zero,

>
> These are where you might find some disagreement out there in the fields


That's what I want to hear. What are the (perceived) risks, and how are they
measured? Show me the money.

--
Lew
 
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Andreas Leitgeb
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      01-18-2008
Lew <(E-Mail Removed)> wrote:
>> Ever so often the reason is: "Never change a running system"

> It's a good principle, except for the part about never changing a running system.

Not much left then ...

>>> Conversion costs are next to zero. Risk is also near zero,

>> These are where you might find some disagreement out there in the fields

> That's what I want to hear. What are the (perceived) risks, and how are they
> measured? Show me the money.


I know of a project, that back in java 1.3 days used a method "assert(...)"
in almost every single class. It was no sophisticated work, to globally
search for that method-name, and either rename it, or make it a proper
assertion, but for some reason, the customers did not want to spend any money
for that work, until the dead-line for java 1.3 was really approaching.

There were, of course, also slight GUI-glitches to solve, where some
default changed (font-size, colors), or setting background color of some
component no longer had any effect, resulting in a white-on-white textfield.
Some of these effects were actually from workarounds for bugs in 1.3, that no
longer worked with 1.4 (again only some of them just weren't necessary anymore
for 1.4).

Then there was some incompatibility with a third-party-library, whose newer
version had dropped a certain needed feature, which they had deprecated, but
without providing an alternative that satisfied the needs, resulting in that
crap having to be replaced.

Even if no line of source were needed to be changed, it still requires at
least a complete(as far as possible) testing walk-through to detect
"suddenly white-on-white" text-elements.

That should be enough - I will not go into more detail. If you don't
believe me, that's not my problem.

 
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Nigel Wade
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      01-18-2008
Lew wrote:

> Andreas Leitgeb wrote:
>> Lew <(E-Mail Removed)> wrote:


>>> Conversion costs are next to zero. Risk is also near zero,

>>
>> These are where you might find some disagreement out there in the fields

>
> That's what I want to hear. What are the (perceived) risks, and how are they
> measured? Show me the money.
>


The risk is breaking existing software. The cost is in determining whether that
risk is real.

Before updating the JVM on a production system it's a good idea to test your
existing software with the new JVM somewhere else. That involves cost, both in
terms of hardware and manpower. Of course there may be other considerations
such as whether the software you need to test is licensed to run anywhere other
than the production server...

--
Nigel Wade, System Administrator, Space Plasma Physics Group,
University of Leicester, Leicester, LE1 7RH, UK
E-mail : http://www.velocityreviews.com/forums/(E-Mail Removed)
Phone : +44 (0)116 2523548, Fax : +44 (0)116 2523555
 
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Arne Vajhj
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      01-19-2008
Chen wrote:
> On 17 Jan, 23:56, Arne Vajhj <(E-Mail Removed)> wrote:
>> Chen wrote:
>>> I want to programmemultithreadingonmulti-coreCPU. What should I do
>>> to fully utilize themulti-core? Will themulti-threads automatically
>>> be assigned to different cores?

>> If you make your app multithreaded, then most modern JVM's and OS's
>> will be able to utilizemulti-core.

>
> Does this mean Windows XP and Java 1.4 can do it automatically?


Yes.

Arne
 
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Arne Vajhøj
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      01-19-2008
Lew wrote:
> Often people will say, "That's the platform I'm stuck with." This begs
> the question of why one is stuck with the platform. What are the reasons?
>
> It can't be acquisition cost, which approximates zero. Labor costs for
> installation are minimal. Conversion costs are next to zero. Risk is
> also near zero, and since the benefits are large, the cost-benefit and
> risk-reward analyses should strongly favor going with a (more) current
> Java version.


Well if fixing all 1.5 language things and testing the entire
app cost a million dollars then you can bet that finance will
ask what benefits that upgrade has.

Arne
 
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Arne Vajhøj
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      01-19-2008
Lew wrote:
> That doesn't apply in this case, since the question was sparked by
> someone needing to write new code.


It may not apply in this case.

But in the real world starting with a blank sheet of paper
is rare.

Maintenance of existing apps or new apps that need to run in the
same environment as existing apps are more the norm than the exception.

Arne
 
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