[Beowulf] [External] Re: Clustering vs Hadoop/spark [EXT]

[Prentice Bisbal]

So "automatic garbage collection" is a lie?

On 11/25/20 6:40 AM, Tim Cutts wrote:
> 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.
>
> 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.
>
> 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.
>
> I’m not sure you can ever actually really get rid of the need to 
> understand memory allocation… you just push the problem around!
>
> Tim
>
>> On 24 Nov 2020, at 18:32, Prentice Bisbal via Beowulf 
>> <beowulf at beowulf.org <mailto:beowulf at beowulf.org>> wrote:
>>
>> 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++
>
> -- 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. 

-- 
Prentice Bisbal
Lead Software Engineer
Research Computing
Princeton Plasma Physics Laboratory
http://www.pppl.gov

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