Algorithm an data Structure in Labview

Hello,
I want to learn implementing algorithm and data stucture using LabVIEW. Is there a book or link some of you may recommend?
thanks

Aristocrate wrote:
you're right altenbach1
however most labview tutorial only teach you how to program with labview; the basics. But none elaborate on how to implement complex data structre like Queues, list, threes, or recursion. That is actually what I want. Same like we observe with other text books for c,c++ and java.
That's probably because LabVIEW does some of these for you. I remember learning the different sort algorithms and how to implement them with trees and other methods. It was all good for academics, but when it came to the real world just use the built in sort function. Same with queues.
If you are sick of the beginner LabVIEW stuff I suggest going to a local user group to try to learn from others. These generally are an intermediate step after you've master the beginner stuff. There are official coarses that go beyond beginner stuff, but they too likely won't focus on algorithms. More often these coarses explain how to make large scale applications, or how to design an application to scale up without painting your self into a corner.
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If 10 out of 10 experts in any field say something is bad, you should probably take their opinion seriously.

Similar Messages

Clusters as data structures

I am looking for the best and simplest way to create and manage data structures in Labview.
Most often I use clusters as data structures, however the thing I don't like about this approach is that when I pass the cluster to a subroutine, the subroutine needs a local copy of the cluster.
If I change the cluster later (say I add a new data member), then I need to go through all the subroutines with local copies of the cluster and make the edit of the new member (delete/save/relink to sub-vi, etc).
On a few occasions in the past, I've tried NI GOOP, but I find the extra overhead associated with this approach cumbersome, I don't want to have to write 'get' and 'set' methods for every integer and string, I like being able to access the cluster/object data via the "unbundle by name" feature.
Is there a simple or clever way of having a single global reference to a data object (say a cluster) that is shared by a group of subroutines and which can then be used as a template as an input or output parameter? I might guess the answer is no because Labview is interpreted and so the data object has to be passed as a handle, which I guess is how GOOP works, and I have the choice of putting in the extra energy up front (using GOOP) or later (using clusters if I have to edit the data structure). Would it be advisable to just use a data cluster as a global variable?
I'm curious how other programmers handle this. Is GOOP pretty widely used? Is it the best approach for creating maintainable LV software ?
Alex

Alex,
Encapsulation of data is critical to maintaining a large program. You need global, but restricted, access to your data structures. You need a method that guarantees serial, atomic access so that your exposure to race conditions is minimimized. Since LabVIEW is inherently multi-threaded, it is very easy to shoot yourself in the foot. I can feel your pain when you mention writing all those get and set VIs. However, I can tell you that it is far less painful than trying to debug a race condition. Making a LabVIEW object also forces you to think through your program structure ahead of time - not something we LabVIEW programmers are accustomed to doing, but very necessary for large program success. I have use three methods of data encapsulation.
NI GOOP - You can get NI GOOP from the tutorial Graphical Object Oriented Programming (GOOP). It uses a code interface node to store the strict typedef data cluster. The wizard eases maintenance. Unfortunately, the code interface node forces you through the UI thread any time you access data, which dramatically slows performance (about an order of magnitude worse than the next couple of methods).
Functional Globals - These are also called LV2 style globals or shift register globals. The zip file attached includes an NI-Week presentation on the basics of how to use this approach with an amusing example. The commercial Endevo GOOP toolkit now uses this method instead of the code interface node method.
Single-Element Queues - The data is stored in a single element queue. You create the database by creating the queue and stuffing it with your data. A get function is implemented by popping the data from the queue, doing an unbundle by name, then pushing the data back into the queue. A set is done by popping the data from the queue, doing a bundle by name, then pushing the data back into the queue. You destroy the data by destroying the queue with a force destroy. By always pulling the element from the queue before doing any operation, you force any other caller to wait for the queue to have an element before executing. This serializes access to your database. I have just started using this approach and do not have a good example or lots of experience with it, but can post more info if you need it. Let me know.
This account is no longer active. Contact ShadesOfGray for current posts and information.

Can I automate the creation of a cluster in LabView using the data structure created in an autogenerated .CSV, C header, or XML file?

Can I automate the creation of a cluster in LabView using the data structure created in an auto generated .CSV, C header, or XML file? I'm trying to take the data structure defined in one or more of those files listed and have LabView automatically create a cluster with identical structure and data types. (Ideally, I would like to do this with a C header file only.) Basically, I'm trying to avoid having to create the cluster by hand, as the number of cluster elements could be very large. I've looked into EasyXML and contacted the rep for the add-on. Unfortunately, this capability has not been created yet. Has anyone done something like this before? Thanks in advance for the help.
Message Edited by PhilipJoeP on 04-29-2009 04:54 PM
Solved!
Go to Solution.

smercurio_fc wrote:
Is this something you're trying to do at runtime? Clusters are fixed data structures so you can't change them programmatically. Or, are you just trying to create some typedef cluster controls so that you can use them for coding? What would your clusters basically look like? Perhaps another way of holding the information like an array of variants?
You can try LabVIEW scripting, though be aware that this is not supported by NI.
Wow! Thanks for the quick response! We would use this cluster as a fixed data structure. No need to change the structure during runtime. The cluster would be a cluster of clusters with multiple levels. There would be not pattern as to how deep these levels would go, or how many elements would be in each. Here is the application. I would like to be able to autocode a Simulink model file into a DLL. The model DLL would accept a Simulink bus object of a certain data structure (bus of buses), pick out which elements of the bus is needed for the model calculation, and then pass the bus object. I then will take the DLL file and use the DLL VI block to pass a cluster into the DLL block (with identical structure as the bus in Simulink). To save time, I would like to auto generate the C header file using Simulink to define the bus structure and then have LabView read that header file and create the cluster automatically. Right now I can do everything but the auto creation of the cluster. I can manually build the cluster to match the Simulink model bus structure and it runs fine. But this is only for an example model with a small structure. Need to make the cluster creation automated so it can handle large structures with minimal brute force. Thanks!

Data Structures and Algorithms in java book

Hi guys,
I want to know a good book which is good for Data Structures and Algorithms in java. I am good at Core java but a beginner for Data Structures in Java. I am a little poor in Data Structures concepts.
Following are the books I have found on the net. Could you help me the choose the best outta them.
1. Data Structures and Algorithms in Java - Mitchell Waite
2. Data Structures in Java - Sandra Anderson
3. Fundamentals of OOP and Data Structures in Java - Richard Weiner & Lewis J. Pinson
4. Object Oriented Data Structures Using Java - Nell Dale, Daniel T. Joyce, Chip Weems

lieni wrote:
I good data structures book doesn't have to be language-specific.Thx DrLazlo, my speachYes.
The OP wrote:
I have access to these books and dont know which one to start with.What I meant is that you shouldn't narrow your search to insist that the book you choose have "Java" in the title.

Looking for an efficient data structur & search algorithm

Hi all
i have a list of digits (international phone network prefixes) with some hundreds to some thousends entries. An entry may be in the form
^00[1-9]{1}[0-9]{0,7}$
I.e. this might be 001, 0041, 00317545, 00317548, 00317549 and so on. Regarding the last three examples, it might even be that there is an additonal 0031754.
What i need a a data structur that allows to match these prefixes against a phonenumber.
I.e. if i have the phonennumber 001123456789 it would match the prefix 001. If i had 00317549111 it would match 00317549.
The easiest way would be to but all prefixes into an Vector or similar and loop over all entries, trying to match the phonenumber with startsWith(). But this wouldn't always result in a absolutely perfect match, since, i.e. for the phonenumber 00317549111 the check against the prefix 0031754 would return a match even if there was a more specific match with the prefix 00317549. But more than that, this simple algorithm is not very efficient.
So i am looking for a more efficient way/pattern to do this. I thought about a kind of tree structure, starting with 00 in the top level, than provding [1-9] in the second level, and [0-9] from third level on. Then on every node it would either store if there is a matching prefix on that level, or if there is a prefix starting with that digits on a lower level or if there is no prefix on that level or any lower.
I.e. when i have the phonenumber 00317549111 it would start at the top level with 00. That would be ok. On the next level it would check if there is a node for digit 3. If there is, it would go one level deeper and check if there is a node for digit 1. If yes, again it would go one level deeper to check if there is a node for digit 7. If that algorithm comes to a level where, for the request digit, it get's a prefix indicator rather than a node indicator, the algortihm would know, that a matching prefix was found and that there is no more specifig match on deeper levels.
One thing i forgot to mention - the prefixes might be read once during startup/init and there it might take some time for building up the datastructur - i don't care about that. But, when running, then the maching process should be as efficient as possible, that's the most important point for me.
What do you think about a pattern like this? Could this be efficient? Do you see other patterns, that might be easier to implement and that might be faster/need less memory?
Thanks a lot for your help.
Cheers, Frank

I would really have gone for your first approach. With mperemsky5's approach you have the loop with (potential) n iterations (Let n be the length of the number) and in each iteration to compute the hash-code for the string which again takes time proportional to the strings length.
The tree approach takes time equal to the length of the prefix and is imho not more complicated.
Perhaps this way:
public class DigitTree
private class Node {
     private Object content;
     private Node[] children = new Node[10];
private Node root = new Node();
public DigitTree() {
public void addPrefix(String prefix, Object value) {
     char[] numberChars = prefix.toCharArray();
     Node node = root;
     for (int i=0; i<numberChars.length; i++) {
          int number = numberChars[i] - '0';
          if (node.children[number] == null) node.children[number] = new Node();
          node = node.children[number];
     node.content = value;
public Object match(String phonenumber) {
     char[] numberChars = prefix.toCharArray();
     Node node = root;
     for (int i=0; i<numberChars.length; i++) {
          int number = numberChars[i] - '0';
          if (node.children[number] == null) return code.content;
          node = node.children[number];
     return node.content;
}The method addPrefix lets you add a prefix to the tree. The content-Object can hold a String or whatever to identify the prefix. If your data is not complete (i.e. if there are numbers for which no prefix exists) you might want to initialize the content-object of a node with a default value (e.g. "not found").
The method match lets you look up a prefix for a given number and returns the Object associated with the prefix..
The code was not tested.
Greetings
Thomas

Need a good Data Structure/ Algorithm

I am working on a small problem that requires me to cache a large amount of key/value pairs of data. I must then do a lookup on the cache for a large number of words one after another until I find a word that is present as a Key and then quit.
The cache is pretty large. About 600 - 1000 words as keys and ints as values.
Is there an existing Data Structure in Java for this? If not, what type of data structure (B-tree etc) is best suited to cache such data and what algorithm should be used for lookup?

The lookup for hashmap is efficient for very large maps up to the amount of memory you have. If you tune the load factor you can minimise the impact of having very large tables.
Another option is to have a fixed array of HashMaps. You can use the hashcode (or your own) to put the key, value into the HashMap. I am not sure if this is actaully any faster, as I believe one is enough, but if you have concern this is what you can do.

Need links for data structure and algorithms.

Hi.
I am just new to java but need to learn data structure and algorithms.
Do your guys got any good links or bbs to learn?
Thanx in advance

http://www.amazon.com/exec/obidos/tg/detail/-/1571690956/ref=cm_huw_sim_1_3/104-7657019-1043968?v=glance
http://www.amazon.com/exec/obidos/tg/detail/-/0534376681/ref=cm_huw_sim_1_4/104-7657019-1043968?v=glance
http://www.amazon.com/exec/obidos/tg/detail/-/0672324539/ref=cm_huw_sim_1_2/104-7657019-1043968?v=glance
http://www.amazon.com/exec/obidos/tg/detail/-/0201775786/qid=1060946080/sr=8-1/ref=sr_8_1/104-7657019-1043968?v=glance&s=books&n=507846
$8 for the first

What is the new data structure for .RTM files in LV8?

We have software that translates our LV
program to another language. Part of that software package reads RTM
files, decodes them, replaces text, and resaves them. That code is
broken for menus that are saved in LV8+, however. What is the new data
structure?
The simple attached zip file has vi's which
are not ours but serve to illustrate the point. If it's run on an
older RTM file, it correctly outputs and XML version of it, on newer
RTM files it just throws an error.
-- This is the second time I posted this. I was curious what the Solution? icon did on somebody elses post and I apparently marked the whole thread as solved (there should really be an undo on that feature btw --
Attachments:
RunTime_Menu_to_XML.zip ‏33 KB

Hi Thomas,
What error are you getting when running the program? I was actually able to run it without errors in LV 8.6.
There are ways to programmatically read and customize RTM files in LabVIEW. I hope that the following links will help:
http://zone.ni.com/reference/en-XX/help/371361B-01/lvhowto/customizing_shortcut_menus_programm/
http://digital.ni.com/public.nsf/allkb/17803AA31C8C07C986256CFD0080D609?OpenDocument
Cheers,
Marti C
Applications Engineer
National Instruments
NI Medical

Is timesten still using T-tree as data structure?

I just come across this paper - http://www.memdb.com/paper.pdf , this researcher do some experiments and showing that using concurrent B-tree algorithm is actually faster than T-tree operation. How do you think about this paper? Do you think actually he is using a inefficient algorithm to access T-tree? Or, Timesten already know the limitation of T-tree and have changed the internal data-structure?

Yes, we are aware of the comparisons between T-Trees, concurrent B-trees etc. At the moment TimesTen still uses T-trees but this may change in the future :-)
Chris

Data Structures in SQL Server

Friends,
I am giving a session on "Data structures and SQL Server" for one of the SQL Server communities in India.
My idea is to explain high level concepts of data structures (Stacks, Queues, Linked lists, Trees, Graphs etc.)
here are my questions.
Like to know how data structure concepts are implemented SQL Server components (in a high level).
Here are some hints in my mind:
1. Queues - SQL Server - DMVs for Processor Queue length, Disk Queue length etc.
2. Linked Lists - SQL Server - Previous and Next page pointers in Page headers (and DBCC IND)
3. Trees - SQL Server - Btrees in Indexes (DBCC IND and DBCC PAGE of Index pages)
3. Linear Search - SQL Server - Table Scan
4. Binary Search - SQL Server - Index Seek
What i need is:
1. Sorting algorithm used in SQL Server?
2. Stack concept used in SQL Server? I think No
3. what else data structure concepts are implemented in SQL Server (that can be demonstrated)
Note: level: 300 - Intermediate to Advanced.
Thanks in advance
Ramkumar
[email protected]
Ramkumar Gopal Living For SQL Server Blog: http://www.sqlservercentral.com/blogs/livingforsqlserver/ Facebook: https://www.facebook.com/#!/groups/livingforsqlserver/ Twitter: https://twitter.com/LivingForSQL

Hello,
Take a look at some structures created for In-Memory OLTP (hash indexes, etc.)
http://download.microsoft.com/download/5/F/8/5F8D223F-E08B-41CC-8CE5-95B79908A872/SQL_Server_2014_In-Memory_OLTP_TDM_White_Paper.pdf
BUF Structures.
http://blogs.msdn.com/b/karthick_pk/archive/2013/03/16/sql-server-memory.aspx
Hope this helps.
Regards,
Alberto Morillo
SQLCoffee.com

Implementing a Graph Data Structure

First time posting here, I was introduced to LabVIEW while participating in FIRST.
I was reading about Graph Data Structures, and wanted to see if I could use them in LabVIEW, as it looked like a good way to relate information. Unfortunately, it appears that the straight forward way that I attempted will not work. I tried creating a typedef which consisted of a cluster of two elements, an array of linked nodes and an array of edge weights. Alas, I found you can't have recursive data types, as the array of linked nodes in the typedef needed to be the same as the typedef. I know why this is after a bit of searching, but I was wondering if there was a way to get around this. From my research, it seems like using a root class and a child class is one possible, but advanced way of doing it.
I am currently thinking of just representing the linked nodes of a node as an array of index numbers which you can use to get the referenced nodes from the graph array. This means that the graph array cannot be sorted or otherwise modified so that the index numbers won't work, you can only add objects onto the end. Is this thinking right, or is there a different way to go about this?
Solved!
Go to Solution.

Not an easy problem, as recursion is not native to LV programming (much less than any other language I used except assembler).
But the solution to your index number problem is to use 'keys'. Each node should have a unique key (number), so you can adress it (search for the key) even if the array is sorted in some way.
Again, it is not native to LV. This means, that you need to program the logic other languages use for that on your own (pseudo-pointers, handles, keys, hashes).
From a practical side: I would not implement the graph in LV itself but access a graph from some other source (data base?) via an interface (ActiveX, .NET). To learn a bit more about how to do it, try playing around with the tree control (it is a limited graph).
Felix
www.aescusoft.de
My latest community nugget on producer/consumer design
My current blog: A journey through uml

Relationship between Dynamic Memory Heap and Heap Data Structure

This question is not strictly related to Java, but rather to programming in general, and I tend to get better answers from this community than any where else.
Somehow, my school and industry experience have somehow not given me the opportunity to explore and understand heaps (the data structure), so I'm investigating them now, and in particular, I've been looking at applications. I know they can be used for priority queues, heap sorts, and shortest path searches. However, I would have thought that, obviously, there must be some sort of relationship between the heap data structure, and the dynamic memory heap. Otherwise, I can think of no good reason why the dynamic memory heap would be named "heap". Surprisingly, after searching the web for 90 minutes or so, I've seen vague references, but nothing conclusive (trouble seems to be that it's hard to get Google to understand that I'm using the word "heap" in two different contexts, and similarly, it would not likely understand that web authors would use the word in two different contexts).
The Java Virtual Machine Spec is silent on the subject, as "The Java virtual machine assumes no particular type of automatic storage management system, and the storage management technique may be chosen according to the implementor's system requirements."
I've seen things like:
[of dynamic memory] "All the blocks of a particular size are kept in a sorted linked list or tree (I extrapolate that sorted tree could imply heap)"
[of dynamic memory] "The free and reserved areas of memory are maintained in a data structure similar to binary trees called a heap"
[of dynamic memory] "This is not related to the heap data structure"
[of dynamic memory] "Not to be confused with the data structure known as a "heap"
[of data structure] "Not to be confused with the dynamic memory pool, often known as TheHeap"
At this point, I've come to surmise that some (but not all) memory management algorithms use heaps to track which (pages? blocks? bytes?) of memory are used, and which are not. However, the point of a heap is to store data so that the max (or min) key is at the root of the heap. But we might want to allocate memory of different sizes at different times, so it wouldn't make sense to key on the amount of available memory in a particular region of the free store.
I must assume then that there would be a different heap maintained for each size of memory block that can be allocated, and the key must have something to do with the attractiveness of the particular memory block in the heap (perhaps the lowest address, resulting, hopefully, in growing the free store space less often, leaving more space for the stack to grow, or perhaps keyed based on the fragmentation, to hopefully result in less fragmentation, and therefore more efficient use of the memory space, or perhaps based on page boundaries, keeping as much data in the same page as possible, etc).
So at this point, I have a few questions I've been unable to resolve completely:
1. Am I correct that the heap was so named because (perhaps at one point in time), a heap is/was commonly used to track the available memory in the free store?
2. If so, would it be correct that there would be a heap per standard block size?
3. Also, at what level of granularity would a heap typically be used (memory page, memory blocks, individual words (4-bytes))?
4. What would be the most likely property one would use as a key. That is, what makes the root item on the heap ideal?
5. Would a industrial strength system like the jvm use a (perhaps modified or tuned) heap for this sort of task, or would this typically be too naive for an real world solution today?
Any insight would be awesome!
Thanks,
A.

jschell wrote:
I think you are not only mixing terms but domains.
For starters the OS allocs memory. Applications, regardless of language, request memory from the OS and use it in various ways.
There are many variations of the term "heap" like the following.
[http://en.wikipedia.org/wiki/Heap_(data_structure)]
[http://en.wikipedia.org/wiki/Dynamic_memory_allocation]
A java VM will request memory from the OS (from a 'heap') and use it in its application 'heap' (C/C++) and then create the Java 'heap'. There can be variations of that along the way that can and likely will include variations of how each heap is used, potentially code that creates its own heap, and potentially other allocators which use something which is not a heap.This last part, I find a bit confusing. By "use something which is not a heap", do you mean the heap data structure, or the dynamic memory pool meaning of heap? If the former, then you would be implying that it would be common for a heap data structure to be used to manage the heap dynamic memory pool. If the latter, what would this "something which is not a heap" be? The best definition of "heap" I've found simply states that it is a pool of memory that can be dynamically allocated. If there is some other way of allocating dynamic memory, then it would suggest that the previous definition of "heap" is incomplete.
>
So to terms.
1. Am I correct that the heap was so named because (perhaps at one point in time), a heap is/was commonly used to track the available memory in the free store?Which 'heap'? The VM one? It is probably named that because the implementors of the Sun VM were familar with how C++ and Smalltalk allocated memory.Okay, but that begs the question, was the heap in C++ and/or Smalltalk so named for the above queried reason?
>
2. If so, would it be correct that there would be a heap per standard block size?Not sure what you are referring to but probably a detail of the implementation. And since there are different levels the question doesn't mean much.
However OS allocations are always by block if that helps. After that it requires making the question much, much more specific.
3. Also, at what level of granularity would a heap typically be used (memory page, memory blocks, individual words (4-bytes))?Again not specific enough. A typical standard implementation of heap could not be at the word level. And it is unlikely, but not impossible, that variations would support word size allocations.
The VM heap might use word boundaries (but not size), where the application heap certainly does (word boundary.)My understanding of it is that the application would request blocks from the OS, and then something like malloc would manage the memory within the allocated blocks. malloc (or whatever equivalent Java uses) would have to keep track of the memory it has allocated somehow, and I would think it would have to do this at the word level, since it's most commonly going to allocate memory at the word level to be references to other objects, etc.
So I guess my question here would really be, if the dynamic memory heap is so named because there has been a memory management strategy that relied upon a heap data structure (which I've found no proof, but have found some suggestive literature), then would that probably have applied at the OS Page Fault level, tracking allocated blocks, or would that have applied at the malloc level, allocating individual words as necessary?
>
4. What would be the most likely property one would use as a key. That is, what makes the root item on the heap ideal?"Key" is not a term that will apply in this discussion.
You appear to be referring to strategies for effective allocation of memory such as allocations from different regions by size comparison.
It is possible that all levels might use such an allocator. General purpose applications do not sort allocations though (as per your one reference that mentions 'key'.) Sorry, I got the term "key" from an article I read regarding heaps, that indicates that a "key" is used to sort the elements, which I guess would be a more generalized way to make a heap than assuming a natural ordering on the elements in the heap. I'm not sure if the terminology is standard.
>
5. Would a industrial strength system like the jvm use a (perhaps modified or tuned) heap for this sort of task, or would this typically be too naive for an real world solution today?Again too indefinite. The Sun VM uses a rather complicated allocator, the model for which originated after years of proceeding research certainly in Smalltalk and in Lisp as well, both commercially and academically.
I am sure the default is rules driven either explicitly or implicitly as well. So it is self tuning.
There are command line options that allow you to change how it works as well.I guess perhaps I could attempt to clarify my initial question a bit.
There is a 1:1 correspondence between the runtime stack, and a stack data structure. That is, when you call a function, it pushes a stack frame onto the runtime stack. When you return from a function, it pops a stack frame from the runtime stack. This is almost certainly the reasons the runtime stack is named as it is.
The question is, is there or has there ever been a 1:1 correspondence between some aspect of the dynamic memory heap or how it is managed, and a heap data structure? If so, it would explain the name, but I'm a bit puzzled as to how a heap data structure would be of assistance in creating or managing the dynamic memory heap. If not, on the other hand, then does anybody know where the name "heap" came from, as it applies to the dynamic memory pool?
A.

Trees Data Structures in Java

Hi all !
Currently I�m developing a Java software that requires a Tree data structure. Searching through Java API I�ve found classes like TreeMap and TreeSet, but although these classes seens to use tree structure behind what they really provide are linear data structure, not a tree data structure. My question is if there is a public and free Java tree data structure that permits to do activities such as:
- Search for a particular node (efficiently)
- Insert children to any node
- Maintain one Object in each node
Simple like this ! It must have something like this in Java, but I just can�t find it and I�m just too lazy to implement it :) ! Anyone can help me ?
Thanks in advance !

Mel,
I�ve seen javax.swing.tree.TreeModel and its seens more like an implementation of Control in swing MVC (Model Vision Control) swing paradigm for JTree. It has listeners generated for manipulation events for example. It uses javax.swing.tree.DefaultMutableTreeNode for its nodes, and maybe I could use this class for the nodes of my tree since it has many useful operations. However still I miss a node searching operation that this class doesn�t have.
Yes my problem is a simple Tree, but it is simple now and it might become much more complex, demanding more operations on the tree and specially efficient searching algorithms. Thats why I�m looking for a complete solution and I prefer something that is already done and well tested :) !
Thanks for your tip !

Data structure to hold frequencies or counts

i need to know if there is a data structure with a supporting algorithm that can query counts. for example, if i have two variables, eye color and hair color, where the values of eye color are brown, blue, green, hazel, and the values of hair color are black and blonde, i'd like to set the frequencies for the combination of these values and also be able to query very quickly the frequencies for the combination i.e. how many people had brown eyes and black hair?
what i need could be accomplished easily using a database i.e. select count(*) as total from tbl where eye_color='brown' and hair_color='black'. however, i have tried using various databases (i.e. oracle, ms sql server, mysql), and the performance is poor when the number of variables or rows grow. also, a database approach introduces various complexities (i.e. trying to code database vendor agnostic coding, learning how to index the fields to optimize reads, figuring out field types or efficient storage, etc...).
any help is appreciated. thanks.

You should check apache-commons' MultiKey and MultiKeyMap:
http://commons.apache.org/collections/api-release/org/apache/commons/collections/map/MultiKeyMap.html
Also adding an index to a database column is quite straightforward, there are many optimization tips available, e.g.:
http://www.databasejournal.com/features/mssql/article.php/1443581
http://www.databasejournal.com/features/mysql/article.php/10897_1382791_1

Hashtable like data structure

I am just trying to find out if anyone knows of a data structure that is similar to a hashtable, with the exception that I need to be able to access a KEY given a VALUE, as well as the standard access of a VALUE given a KEY.
Hashtable only allows lookup by KEY, not VALUE.
Thanks, Jason

And not only that, Hashtable allows more than one key to have the same value. The simplest solution (not algorithm) for your problem is an object that wraps two Hashtables, one to handle the A->B mapping and the other to handle the B->A mapping.
Unless your mappings are not 1-to-1, such as if you had A,B and C,D and E,B in which case your value-to-key mapping for value B would somehow have to return both A and E.

Algorithm an data Structure in Labview

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