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Groups > comp.lang.java.programmer > #14658

Re: multithreaded cache?

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Am 17.05.2012 12:06, schrieb Robert Klemme:
> On 05/17/2012 11:54 AM, Robert Klemme wrote:
>> On 05/15/2012 11:14 AM, bugbear wrote:
>>> However, if the underlying function is slow
>>> and/or resource hungry (consider cacheing
>>> a ray traced image!) many threads can
>>> end up calling the real function (second
>>> and subsequent threads to the first get a miss
>>> during the first threads call to the underlying function).
>>>
>>> "obviously..." what I want is for only
>>> the thread that FIRST has a cache miss
>>> calls the underlying function, whilst other
>>> threads (for the same key) wait.
>>
>> I provide a variant of Silvio's, Eric's and Daniel's solution which
>> should yield higher throughput because it works without read write
>> locking. You can find it as gist in case the code is garbled in the
>> newsgroup posting:
>> https://gist.github.com/2717818
>
> There was one important detail missing. This is the corrected code (gist
> is updated as well):
>
[snip]
The important detail obiously is the extra check with the "here" flag.
Would you mind explaining why that is necessary? Everyone seems to have
got it, but I must admit I haven't. Why is it not enough that
Reference#get() is synchronized? As you yourself have missed this at
your first attempt, I hope the reason isn't trivial...
-- Sebastian

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Thread

multithreaded cache? bugbear <bugbear@trim_papermule.co.uk_trim> - 2012-05-15 10:14 +0100
  Re: multithreaded cache? Silvio Bierman <silvio@moc.com> - 2012-05-15 11:41 +0200
    Re: multithreaded cache? Roedy Green <see_website@mindprod.com.invalid> - 2012-05-15 15:57 -0700
      Re: multithreaded cache? Daniel Pitts <newsgroup.nospam@virtualinfinity.net> - 2012-05-15 16:13 -0700
        Re: multithreaded cache? Silvio Bierman <silvio@moc.com> - 2012-05-16 01:22 +0200
      Re: multithreaded cache? Silvio Bierman <silvio@moc.com> - 2012-05-16 01:19 +0200
        Re: multithreaded cache? Eric Sosman <esosman@ieee-dot-org.invalid> - 2012-05-15 20:26 -0400
          Re: multithreaded cache? Arved Sandstrom <asandstrom3minus1@eastlink.ca> - 2012-05-15 21:41 -0300
          Re: multithreaded cache? Silvio Bierman <silvio@moc.com> - 2012-05-16 09:26 +0200
            Re: multithreaded cache? "Mike Schilling" <mscottschilling@hotmail.com> - 2012-05-26 14:54 -0700
        Re: multithreaded cache? Roedy Green <see_website@mindprod.com.invalid> - 2012-05-16 22:03 -0700
          Re: multithreaded cache? Silvio Bierman <silvio@moc.com> - 2012-05-21 15:25 +0200
  Re: multithreaded cache? Eric Sosman <esosman@ieee-dot-org.invalid> - 2012-05-15 08:22 -0400
  Re: multithreaded cache? Daniel Pitts <newsgroup.nospam@virtualinfinity.net> - 2012-05-15 09:56 -0700
  Re: multithreaded cache? bugbear <bugbear@trim_papermule.co.uk_trim> - 2012-05-16 14:33 +0100
  Re: multithreaded cache? Robert Klemme <shortcutter@googlemail.com> - 2012-05-17 11:54 +0200
    Re: multithreaded cache? Robert Klemme <shortcutter@googlemail.com> - 2012-05-17 12:06 +0200
      Re: multithreaded cache? Daniel Pitts <newsgroup.nospam@virtualinfinity.net> - 2012-05-17 09:51 -0700
        Re: multithreaded cache? Robert Klemme <shortcutter@googlemail.com> - 2012-05-17 20:48 +0200
      Re: multithreaded cache? Sebastian <sebastian@undisclosed.invalid> - 2012-05-20 01:35 +0200
        Re: multithreaded cache? Sebastian <sebastian@undisclosed.invalid> - 2012-05-20 01:48 +0200
          Re: multithreaded cache? Lew <noone@lewscanon.com> - 2012-05-19 18:11 -0700
    Re: multithreaded cache? Silvio Bierman <silvio@moc.com> - 2012-05-18 20:42 +0200
      Re: multithreaded cache? Robert Klemme <shortcutter@googlemail.com> - 2012-05-18 23:45 +0200
        Re: multithreaded cache? Eric Sosman <esosman@ieee-dot-org.invalid> - 2012-05-18 18:31 -0400
          Re: multithreaded cache? Daniel Pitts <newsgroup.nospam@virtualinfinity.net> - 2012-05-18 22:15 -0700
            Re: multithreaded cache? Eric Sosman <esosman@ieee-dot-org.invalid> - 2012-05-19 07:09 -0400
          Re: multithreaded cache? Robert Klemme <shortcutter@googlemail.com> - 2012-05-19 12:33 +0200
            Re: multithreaded cache? Lew <noone@lewscanon.com> - 2012-05-19 14:24 -0700
              Re: multithreaded cache? Robert Klemme <shortcutter@googlemail.com> - 2012-05-21 21:15 +0200
                Re: multithreaded cache? Lew <noone@lewscanon.com> - 2012-05-23 23:11 -0700
                Re: multithreaded cache? Robert Klemme <shortcutter@googlemail.com> - 2012-05-24 23:05 +0200
                Re: multithreaded cache? Gene Wirchenko <genew@ocis.net> - 2012-05-24 20:11 -0700
                Re: multithreaded cache? Robert Klemme <shortcutter@googlemail.com> - 2012-05-25 17:42 +0200
                Re: multithreaded cache? Arved Sandstrom <asandstrom3minus1@eastlink.ca> - 2012-05-25 07:09 -0300
        Re: multithreaded cache? Silvio Bierman <silvio@moc.com> - 2012-05-21 15:21 +0200
  Re: multithreaded cache? Kevin McMurtrie <mcmurtrie@pixelmemory.us> - 2012-05-24 23:22 -0700
    Re: multithreaded cache? Robert Klemme <shortcutter@googlemail.com> - 2012-05-25 17:36 +0200
      Re: multithreaded cache? Kevin McMurtrie <mcmurtrie@pixelmemory.us> - 2012-06-02 12:27 -0700
        Re: multithreaded cache? Robert Klemme <shortcutter@googlemail.com> - 2012-06-02 21:54 +0200

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