Michael, I can offer a tiny bit of insight into OpenJUMP's selection code. What I'm about to tell you is part of what I hope to document about the selection system when I'm done squishing bugs on my Super Select Tool.
OpenJUMP uses collections and something called a CollectionMap quite extensively in the selection code. (A CollectionMap is a utility class used by vivid Solutions in JUMP. It is a Map whose values are other Collections.) At a bare minimum OpenJUMP maintains a single CollecctionMap for each layer that contains selected items. The keys of this CollectionMap are the selected Features and the values are another Collection. The Collections stored as values are LinkedLists (I believe) and they contain the "items" of the selected Features. In most cases this is just the JTS Geometry object representing the selected Feature, but in some cases it might be the "parts" of a JTS Geometry. (A sement of a polygon ring, for example.) As far as I can tell the CollectionMap is not deleted once it is created (as long as the instance of OpenJUMP is running) although it may be "empty" if no features in the correspongind layer are selected. If I remember correctly several other collections are created in the process of "drilling down" to the correct "items" to select based on user actions. I know that I am a rookie code slinger, but I found that the selection code in OpenJUMP was a real challenge to understand. I hope to supplement/add some Javadoc comments that might make it easier on the next programmer to venture that direction. I hope my tiny bit of info about the selection code will shed some light on the topic being discussed currently. The Sunburned Surveyor On 10/8/07, Michaël Michaud <[EMAIL PROTECTED]> wrote: > Hi Larry, > > May be I did not understand your solution, but I think like SS, that > selecting with a fence is not a general solution for the selection > problem. A selection can be the result of a query or any set of features > without any particular spatial relationship. > I wonder why collections containing selection are so "huge". Basically, > a selection should be a set of handles (or a little more to be able to > manage geometry parts). > In the case of a large point layer without attribute, the selection size > may be comparable to the feature layer size, but it should stay smaller, > and it is really a worst case. > Maybe there are other reasons why the selection is so large and slow : > hard copy of features, cache, undo/redo management ? > > Anyway, thanks for the continuous improvement of OpenJUMP performances. > > Michaël > > Larry Becker a écrit : > > > Hi SS, > > > > I agree that the problem with selection is the large collections > > being generated. "Parts" are only part of the problem and it is a bit > > late to stop supporting this capability. Optimizations are always > > possible, but only if you have a clear understanding of what you are > > optimizing and use benchmarks for metrics. > > > > Larry > > > > On 10/8/07, *Sunburned Surveyor* <[EMAIL PROTECTED] > > <mailto:[EMAIL PROTECTED]>> wrote: > > > > This sounds like a great solution Larry, but I was wondering if you > > might be able to confirm why selection requires more memory than a > > fence. > > > > Is it because when you use "selection" a bunch of Java collections > > are > > created, whereas when you use a fence, you are just creating a > > geometry? Is it because with the fence no data structures for the > > features within the fence are created until you actually want to do > > something? > > > > The only problem I see with using a fence is that it wouldn't allow > > complex selections. (For example, if I use a fence all the features > > are the fence are in the "quasi-selection".I can't go in an remove > > some items from the quasi-selection. Does this make sense?) > > > > I worked with some of the selection code recently, and it seemed very > > complex to me. There were so many collections being used in the code I > > had to write the purpose of each one down on a scratch pad so I could > > keep track. It seems that most of this complexity was a result of > > OpenJUMP's ability to select parts of Features, and not being > > restricted to selection of whole features. > > > > I wonder if we couldn't come up with a much simpler selection system > > that only selected whole features. We could probably do this using a > > single collection that stored only the FID of a Feature, or an object > > reference to the Feature. A collection of a couple million FID values > > would only be a couple of MB correct? > > > > Perhaps your idea with the fence is best, but I'm thinking it might be > > better to address the complexity in the selection system itself. > > > > I wonder how much people are using OpenJUMP's ability to select > > "parts" of features. > > > > Just my thoughts. I don't think it would take me long to cook up the > > simple "whole-feature-selection-only" system I am talking about. > > > > The Sunburned Surveyor > > > > On 10/8/07, Stefan Steiniger <[EMAIL PROTECTED] > > <mailto:[EMAIL PROTECTED]>> wrote: > > > simple solution and well thought :) > > > > > > we should go for > > > > > > stefan > > > > > > Larry Becker wrote: > > > > > > > Hi, > > > > > > > > Recent work with Extract Layers by Geometry Type, and improving > > > > OpenJump's support for very large selections, has convinced me > > that > > > > JUMP needs a mechanism for dealing with subsets of large layers. > > > > Although the selection mechanism is very flexible, it is very > > > > expensive in terms of memory and processing. To seem what I mean, > > > > consider Arnd's million point layer problem. To break the > > layer into > > > > more manageable pieces, he tried to select some of the points > > and move > > > > them to another layer. When this is done with such a large > > selection, > > > > the UI must build gigantic data structures. The result is an > > > > extremely slow response or an out of memory error. > > > > > > > > An approach that might work for some problems is to use the > > Fence tool > > > > to indicate a subset of the data that can be used in place of a > > > > selection. The advantage is that no data structures are > > needed and > > > > there are no selection handles to draw. I was thinking of > > producing > > > > another Layer Extract plugin that would extract features in > > the Fence > > > > to a new layer. By coding support methods in a utility class, we > > > > could gradually add support for "features in fence" subsets to the > > > > other tools. > > > > > > > > What do you think? > > > > > > > > regards, > > > > > > > > Larry Becker > > > > > > > > -- > > > > http://amusingprogrammer.blogspot.com/ > > > > > > > > > > > >------------------------------------------------------------------------ > > > > > > > > > > > >------------------------------------------------------------------------- > > > >This SF.net email is sponsored by: Splunk Inc. > > > >Still grepping through log files to find problems? Stop. > > > >Now Search log events and configuration files using AJAX and a > > browser. > > > >Download your FREE copy of Splunk now >> http://get.splunk.com/ > > > > > > > > > > > >------------------------------------------------------------------------ > > > > > > > >_______________________________________________ > > > >Jump-pilot-devel mailing list > > > >Jump-pilot-devel@lists.sourceforge.net > > <mailto:Jump-pilot-devel@lists.sourceforge.net> > > > >https://lists.sourceforge.net/lists/listinfo/jump-pilot-devel > > <https://lists.sourceforge.net/lists/listinfo/jump-pilot-devel> > > > > > > > > > > > > > > > > > > > > > ------------------------------------------------------------------------- > > > This SF.net email is sponsored by: Splunk Inc. > > > Still grepping through log files to find problems? Stop. > > > Now Search log events and configuration files using AJAX and a > > browser. > > > Download your FREE copy of Splunk now >> http://get.splunk.com/ > > > _______________________________________________ > > > Jump-pilot-devel mailing list > > > Jump-pilot-devel@lists.sourceforge.net > > <mailto:Jump-pilot-devel@lists.sourceforge.net> > > > https://lists.sourceforge.net/lists/listinfo/jump-pilot-devel > > > > > > > > > ------------------------------------------------------------------------- > > This SF.net email is sponsored by: Splunk Inc. > > Still grepping through log files to find problems? Stop. > > Now Search log events and configuration files using AJAX and a > > browser. > > Download your FREE copy of Splunk now >> http://get.splunk.com/ > > _______________________________________________ > > Jump-pilot-devel mailing list > > Jump-pilot-devel@lists.sourceforge.net > > <mailto:Jump-pilot-devel@lists.sourceforge.net> > > https://lists.sourceforge.net/lists/listinfo/jump-pilot-devel > > <https://lists.sourceforge.net/lists/listinfo/jump-pilot-devel> > > > > > > > > > > -- > > http://amusingprogrammer.blogspot.com/ > > > >------------------------------------------------------------------------ > > > >------------------------------------------------------------------------- > >This SF.net email is sponsored by: Splunk Inc. > >Still grepping through log files to find problems? Stop. > >Now Search log events and configuration files using AJAX and a browser. > >Download your FREE copy of Splunk now >> http://get.splunk.com/ > > > >------------------------------------------------------------------------ > > > >_______________________________________________ > >Jump-pilot-devel mailing list > >Jump-pilot-devel@lists.sourceforge.net > >https://lists.sourceforge.net/lists/listinfo/jump-pilot-devel > > > > > > > ------------------------------------------------------------------------- > This SF.net email is sponsored by: Splunk Inc. > Still grepping through log files to find problems? Stop. > Now Search log events and configuration files using AJAX and a browser. > Download your FREE copy of Splunk now >> http://get.splunk.com/ > _______________________________________________ > Jump-pilot-devel mailing list > Jump-pilot-devel@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/jump-pilot-devel > ------------------------------------------------------------------------- This SF.net email is sponsored by: Splunk Inc. Still grepping through log files to find problems? Stop. Now Search log events and configuration files using AJAX and a browser. Download your FREE copy of Splunk now >> http://get.splunk.com/ _______________________________________________ Jump-pilot-devel mailing list Jump-pilot-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/jump-pilot-devel
