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<p class="MsoNormal"><span style="mso-fareast-language:EN-US">I think a perfect example of what you are describing below is Minecraft. I haven’t take a dive into the mechanics of how it works code wise but it is an interesting game for sure but at times can
be clunky unfortunately.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US">Regards,<o:p></o:p></span></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US">Jonathan<o:p></o:p></span></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US"><o:p> </o:p></span></p>
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<p class="MsoNormal"><b><span lang="EN-US">From:</span></b><span lang="EN-US"> Tim Cutts <tjrc@sanger.ac.uk>
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<b>Sent:</b> 25 November 2020 13:04<br>
<b>To:</b> Jonathan Aquilina <jaquilina@eagleeyet.net><br>
<b>Cc:</b> Prentice Bisbal <pbisbal@pppl.gov>; Beowulf <beowulf@beowulf.org><br>
<b>Subject:</b> Re: [Beowulf] [External] Re: Clustering vs Hadoop/spark [EXT]<o:p></o:p></span></p>
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<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">It depends on how long the object lives. If it’s still being used after a certain number of garbage collection cycles, it gets moved to tenured space, and will never be garbage collected until the tenured space is full, i.e. you’ve used
everything you gave Java with -Xmx. OK, it’s not a real memory leak, but it causes the java application to use more memory than it needs to.
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<p class="MsoNormal">There is a genuine memory leak in the code space that I’ve seen before; some code does something I don’t understand to do with re-allocated classes, and that does cause a genuine memory leak that can never be garbage collected at all. I
don’t remember the details though, and never understood it when I did remember them.<o:p></o:p></p>
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<p class="MsoNormal">Tim<o:p></o:p></p>
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<p class="MsoNormal">On 25 Nov 2020, at 11:51, Jonathan Aquilina <<a href="mailto:jaquilina@eagleeyet.net">jaquilina@eagleeyet.net</a>> wrote:<o:p></o:p></p>
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<p class="MsoNormal">Tim correct me if I am wrong here.<o:p></o:p></p>
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<p class="MsoNormal"> <o:p></o:p></p>
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<p class="MsoNormal">Memory is allocated for as long as the object is being called or do you mean the memory is always allocated regardless of the object being in scope and that part of the programme being used or not?<o:p></o:p></p>
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<p class="MsoNormal">Regards,<o:p></o:p></p>
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<p class="MsoNormal">Jonathan<o:p></o:p></p>
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<p class="MsoNormal"><b><span lang="EN-US">From:</span></b><span class="apple-converted-space"><span lang="EN-US"> </span></span><span lang="EN-US">Beowulf <<a href="mailto:beowulf-bounces@beowulf.org">beowulf-bounces@beowulf.org</a>><span class="apple-converted-space"> </span><b>On
Behalf Of<span class="apple-converted-space"> </span></b>Tim Cutts<br>
<b>Sent:</b><span class="apple-converted-space"> </span>25 November 2020 12:40<br>
<b>To:</b><span class="apple-converted-space"> </span>Prentice Bisbal <<a href="mailto:pbisbal@pppl.gov">pbisbal@pppl.gov</a>><br>
<b>Cc:</b><span class="apple-converted-space"> </span>Beowulf <<a href="mailto:beowulf@beowulf.org">beowulf@beowulf.org</a>><br>
<b>Subject:</b><span class="apple-converted-space"> </span>Re: [Beowulf] [External] Re: Clustering vs Hadoop/spark [EXT]</span><o:p></o:p></p>
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<p class="MsoNormal">Except of course, you do really. Java applications can end up with huge memory leaks because the programmers really need to understand the mechanism when objects get moved from Eden and Survivor space into Tenured space.<o:p></o:p></p>
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<p class="MsoNormal">Tenured space never decreases, so every object which ends up there is allocated memory for the life of the process. If that was actually an ephemeral object, tough, you’ve lost the memory.<o:p></o:p></p>
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<p class="MsoNormal">So ideally, the programmer needs to understand the size of their pile of ephemeral objects and make sure the Eden/Survivor spaces are large enough, otherwise they will have a memory leak. If they make the ephemeral spaces too large, though,
garbage collection takes more time and performance decreases, so it’s a balance.<o:p></o:p></p>
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<p class="MsoNormal">I’m not sure you can ever actually really get rid of the need to understand memory allocation… you just push the problem around!<o:p></o:p></p>
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<p class="MsoNormal">Tim<o:p></o:p></p>
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<p class="MsoNormal">On 24 Nov 2020, at 18:32, Prentice Bisbal via Beowulf <<a href="mailto:beowulf@beowulf.org">beowulf@beowulf.org</a>> wrote:<o:p></o:p></p>
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<p class="MsoNormal"><span style="font-size:9.0pt;font-family:"Helvetica",sans-serif">Also, with Java, you don't have to worry about low-level issues like freeing and allocating memory and doing pointer arithmetic. Not having to worry about those low-level
issues allows a student to focus more on the programming concepts. I knew I screw up dereferencing pointers A LOT when learning C and C++</span><o:p></o:p></p>
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<p class="MsoNormal">-- The Wellcome Sanger Institute is operated by Genome Research Limited, a charity registered in England with number 1021457 and a company registered in England with number 2742969, whose registered office is 215 Euston Road, London, NW1
2BE.<span class="apple-converted-space"> </span><o:p></o:p></p>
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<p class="MsoNormal">-- The Wellcome Sanger Institute is operated by Genome Research Limited, a charity registered in England with number 1021457 and a company registered in England with number 2742969, whose registered office is 215 Euston Road, London, NW1
2BE. <o:p></o:p></p>
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