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I have an multi-objective optimization problem which I would like to solve, preferably in Java using evolutionary algorithms.
I use a parametric finite element model with a couple of real or integer input values x1...xn describing for example the geometry of the model. Each parameter can have values in a certain interval, e.g. x1 \in [2,10], x2 \in [1,4], ...
My goal is to find the optimum solution for one or more given criteria which I calculate within the finite element model. So the values of the objective function are calculated by the model.
I basically need a framework where I can define optimization parameters with certain intervals (x1...xn). The framework should build an initial population with starting values for x1...xn for each individual. With those values I create my model for each individual, perform my calculations and give back the values of the target funtion. Than the framework does its job and creates a new offspring population.
Is there an evolutionary algorithm framework in Java that can do that?
I had a quick look at TinyGP, Jenetics and JGAP. But these focus on Genetic Programming and Symbolic Regression problems. Or did I miss something fundamental?
You can look at watchmaker api
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I am looking for a library in java or scala which can do the same clustering like scipy's linkage does.
Performs hierarchical/agglomerative clustering.
The input y may be either a 1d compressed distance matrix or a 2d
array of observation vectors.
If y is a 1d compressed distance matrix, then y must be a (n2)(n2)
sized vector where n is the number of original observations paired in
the distance matrix. The behavior of this function is very similar to
the MATLAB linkage function.
The java libraries I have found (like jblas) are pretty low level lacking of higher order algoritms like linkage. On the other hand I am pretty sure there are some libraries doing that. Would be nice if you could pin point me to one or two.
PS One can find a lot of indviduals implementing some hierarchical clustering, I prefer something more trustable library like commons math if possible. But there I could only find k means clustering.
In the end I am using this library https://github.com/lbehnke/hierarchical-clustering-java
Its not heavyly maintained but passes the comparisment to python and matlab implementations.
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I need an algorithm or preferably a library, that will assist with arranging a diagram. I can already draw my diagrams, I just need arranging.
A diagram consists of one or more different sized rectangles, they may be connected. Some rectangles must have fixed positions, and the goal is to minimize total connection length. For example, this diagram where red squares have a fixed existing position, and where green squares should be positioned to minimize total connection length.
An optimal scenario is for me to input a graph, where nodes are rectangles and edges are connections. Nodes would have a certain size and possibly a fixed position. The output will be a set of XY coordinates.
I would like to know either an algorithm or library for such a task, thank you.
I have already looked briefly at JUNG and Graphviz, but I fail to see how they might solve my problem. Also, the final program will be an Eclipse plugin, so I would like to be able to easily bundle any external dependencies.
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Looking for a high-performance String hashing functions in Java/Scala - something faster than functions from MurmurHash family, doesn't need to be cryptographically strong, only distribute well.
Any suggestions?
You can find very fast hash function implementations for Java, which BTW account internal String implementation (char[] array) to maximize speed, here: https://github.com/OpenHFT/Zero-Allocation-Hashing
The fastest hashing algorithm that fits the bill presently seems to be xxHash. The lz4-java project contains an implementation ported to Java. I don't know whether the Java implementation has been benchmarked against MurmurHash, though; performance optimizations in C++ don't always port to/from Java. (In particular, xxHash contains more array access, so there could be non-negligible bounds-checking overhead.)
Edit: it looks to me like it uses JNI to call the C++ implementation of xxHash, but JNI overhead is non-negligible, so the performance concerns remain.
However, given that Scala includes a MurmurHash function, and that Java contains a faster default hash (about 2x) that is sorta-reasonably distributed sometimes, one does wonder whether it's really necessary. For instance, scala.util.hashing.MurmurHash3 is about as fast as string creation from an array of bytes, and is twice as fast as that if you give it an array of bytes.
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In Java, I have set of expressions like cond1 AND (cond2 OR cond3) AND ( cond 4 OR cond5). I would like to convert it into tree and then evaluate the final boolean answer. I tried searching a lot around java BDD but not able to get any. Any suggestion with sample code ?
A 5-second Google search returned some reasonable-looking results:
JavaBDD
Java Decision Diagram Libraries
What is the best Binary Decision Diagram library for Java?
Is this not what you're looking for?
He means Binary Decision Diagrams.
I've been tinkering with JavaBDD and JBDD/JDD. Both are based on BuDDY (a C library) -- JBDD actually uses the C DLLs for a marginal performance boost.
It looks to me like JavaBDD is more fully-featured (ex. it supports composing BDDs, which is what I need). But there is also no tutorial for it, and while the class docs aren't terrible, frankly I can't figure out how to use it for the most basic of boolean operations (like the problem you pose).
JBDD/JDD requires you to use manual garbage collection, and does weird things like store BDD objects in Java integers -- clearly carry-overs from C. But it has a set of tutorials.
If you want to run your own parser, check out JavaCC.
Here is a nice tutorial to get you started. A bit older, but still valid:
http://www.javaworld.com/jw-12-2000/jw-1229-cooltools.html
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I'm looking for a Java library that is capable of performing spatial calculations on sets of lat/lon data. Here are some of the functions that I'm looking for:
Calculate the Great Circle distance between two points
Determine if a point lies within a simple closed polygon, where the polygon is defined by an ordered list of points
Determine if the line between point "A" and point "B" intersects a simple closed polygon, where the polygon is defined by an ordered list of points
Determine if point "A" is within a certain radius of point "B"
What I'm NOT looking for:
I don't want a library that is dependent upon a database geospatial component, such as Oracle Spatial, and cannot function independently.
I don't want a library whose purpose is to generate graphics/maps/etc. I am building an analysis module for an existing application and the end goal is not to create pretty pictures.
I don't want a library for searching large amounts of spatial data. If it also happens to do this, that's ok, but I'm not going to use that feature.
The organization is planning to acquire a license for Oracle Spatial eventually (so spatial searching will be covered at that point), but for now I need to implement the analysis functions that I have mentioned above on small data sets without relying on database-supplied spatial support.
I believe GeoTools would satisfy your requirements. Note that it does have facilities for doing graphics/maps, but they can be left unused easily enough.
There is a new library Spatial4J that seems to fullfill your needs, it supports various spaces and shapes
Spatial4j is a general purpose spatial / geospatial ASL licensed open-source Java library (...)
I haven't used it so far but the README is complete, and repositery is rather popular, and it's available on maven repositery
I was looking for such spatial library when I end up both on the repo and on this question.
Simplelatlng gives more simple API for this:
https://code.google.com/p/simplelatlng/wiki/GettingStarted
In spite of your desire to avoid a library that is used to draw maps, I'd recommend OpenMap. The com.bbn.openmap.geo package of that library does most if not all of the things you are asking for.
I've used STRtree java class to index by lat lng data and distance queries
https://locationtech.github.io/jts/javadoc/org/locationtech/jts/index/strtree/STRtree.html