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Re: Concurrency question?

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On 07.02.2015 07:29, Kevin McMurtrie wrote:
> In article <54ce6897$0$289$14726298@news.sunsite.dk>,
>   Arne Vajhøj <arne@vajhoej.dk> wrote:
>
>> On 2/1/2015 1:59 AM, Kevin McMurtrie wrote:

>>> I don't recommend ConcurrentHashMap EVER unless you need atomic
>>> conditional updates.  The implementation is expensive and it's still not
>>> entirely lock free.  You need a lot of concurrency from a lot CPU cores
>>> before you'll see it outperform the old Hashtable class.
>>
>> That is not my experience. CHM seems to be as fast or faster than Ht
>> in most cases I have seen.

> size(), isEmpty(), and toArray() are slower and must allocate temporary
> objects.  get() and put() can be comparable in speed to HashMap, minus
> some overhead for the internal sharding used to reduce lock scope.

But then it is entirely dependent on the use case whether one or the 
other is faster (well, no surprises here).  That is quite a different 
statement than the one you made above which gave the impression that CHM 
is only better in some arcane special cases with "a lot of concurrency".

Kind regards

	robert

-- 
remember.guy do |as, often| as.you_can - without end
http://blog.rubybestpractices.com/

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Concurrency question? Knute Johnson <nospam@rabbitbrush.frazmtn.com> - 2015-01-31 10:34 -0800
  Re: Concurrency question? Eric Sosman <esosman@comcast-dot-net.invalid> - 2015-01-31 14:04 -0500
    Re: Concurrency question? Knute Johnson <nospam@rabbitbrush.frazmtn.com> - 2015-01-31 11:23 -0800
  Re: Concurrency question? Arne Vajhøj <arne@vajhoej.dk> - 2015-01-31 14:12 -0500
    Re: Concurrency question? Knute Johnson <nospam@rabbitbrush.frazmtn.com> - 2015-01-31 11:33 -0800
  Re: Concurrency question? v_borchert@despammed.com (Volker Borchert) - 2015-01-31 19:20 +0000
    Re: Concurrency question? Eric Sosman <esosman@comcast-dot-net.invalid> - 2015-01-31 15:42 -0500
      Re: Concurrency question? Knute Johnson <eternal@knutejohnson.com> - 2015-01-31 19:51 -0800
        Re: Concurrency question? Eric Sosman <esosman@comcast-dot-net.invalid> - 2015-02-01 09:24 -0500
  Re: Concurrency question? Kevin McMurtrie <mcmurtrie@pixelmemory.us> - 2015-01-31 22:59 -0800
    Re: Concurrency question? Arne Vajhøj <arne@vajhoej.dk> - 2015-02-01 12:55 -0500
      Re: Concurrency question? Silvio <silvio@internet.com> - 2015-02-01 22:19 +0100
      Re: Concurrency question? Kevin McMurtrie <mcmurtrie@pixelmemory.us> - 2015-02-06 22:29 -0800
        Re: Concurrency question? Knute Johnson <eternal@knutejohnson.com> - 2015-02-07 10:14 -0800
        Re: Concurrency question? Robert Klemme <shortcutter@googlemail.com> - 2015-02-08 19:33 +0100
  Re: Concurrency question? olupot douglas <olupotd3@gmail.com> - 2015-02-07 01:06 -0800
  Re: Concurrency question? Haddock <ffm2002@web.de> - 2015-02-16 06:32 -0800

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