[Cdk-devel] [ cdk-Feature Requests-788636 ] Lazy creation of ChemObject fields reduces memory overhead

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Feature Requests item #788636, was opened at 2003-08-14 12:29
Message generated for change (Comment added) made by steinbeck
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Category: None
Group: None
Status: Open
Priority: 5
Submitted By: Chris Pudney (cpudney)
Assigned to: Nobody/Anonymous (nobody)
Summary: Lazy creation of ChemObject fields reduces memory overhead

Initial Comment:
G'day,



I am working on an applet that includes a JTable that

has a column displaying 2D structure diagrams (I use

CDK to render the structures).   It all works very

nicely until the user tries to load a few thousand

compounds into the applet - the result is an out of

memory exception.



I did some memory profiling with JMP

<http://www.khelekore.org/jmp/> and jProfiler

<http://www.ej-technologies.com/products/jprofiler/overview.html>

and discoverd that the ChemObject class initializes

many empty fields that are seldom/never used but that

consume considerable amounts of memory (as they are

Vectors, Hashtables or Arrays).



I modified ChemObject to initialize these fields to

null and delay creation of them until they are needed

(lazy creation).  This significantly reduced memory

consumption: 3214 compounds went from consuming 156M

down to 39M after implementing lazy creation.



Attached is the modified ChemObject.java (&

CDKConstants.java).  I also reduced the initial sizes

of the pointers and flags arrays and made the fields

private (even subclasses should use the getter/setter

methods rather than access fields directly).



The unit tests all pass.



Regards,

Chris.

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>Comment By: Christoph Steinbeck (steinbeck)
Date: 2003-09-03 10:59

Message:
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The behavior described here could almost be considered a

bug. We should check if this is still the case in the

current version of CDK

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