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
Similar Messages
-
Is there an easy way to select Items randomly from a data structure?
Put simply, I want to implement a "bag" data structure. So, when i select an item I don't know which one i'm going to get. I want to be able to select all the items once (so no replacing of items i.e. selecting the same item twice in one session).
I can think of ways to implement it using random number generators and the like but does anyone know of a simple datastructure that will encapsulate this "bag" functionality and make my life simple. Hash tables maybe? Any pointers appreciated.
Chris.I don't think there is anything like this in the collections framework but writing one as an extension of a vector could be simple. Something like:
public class Bag extends Vector {
private Random _random = new Random();
public Object pickRandom() {
return this.remove(this._random.nextInt(this.size()));
}To add objects to the bag you just use the add(Object o) method (specified by the List interface, implemented by Vector). To "grab" one just call pickRandom(). -
Efficient data structure to implement simple text editor?
I was given this problem in an interview:
What data structure would you use to implement a simple text editor that does these 4 functions:
a) goto(line number)
b) insert(char input,location)
c) delete(location)
d) printAll() //print entire file
Given that i'm such a newb, i was stumped. I came up with making a 2d array that would allow for o(1) time for goto, but o(n) for everything else (shifting everything in the array). there were other downfalls too dealing with space issues and such, but he wanted me to optimize this data structure. I then came up with a linked list of arrays, but that had similar problems.
But thinking about it further is driving me a little crazy so I'm wondering if you guys have any suggestions on how to answer this question...
one thing that came to mind after is to implement the data structure as a binary tree, where each node contains
class Node
char theChar
int position; // ie 0 = first character in the file, and 81 could be the first character in the 2nd line
node left,right,parent;
}so how it works is the cursor would know where the location was so i would know where to delete and insert within the tree.
insert {
//search for location to insert after (log n)
//create new character node and append to current node
//increment position for all subsequent children
delete(x) {
search for x position
if found, remove node and decrement position value for all children
goto(line #) {
return line # * 80 (or whatever max length for a single line)
}the major problem i see here is balancing the tree after every insert/delete
Thanks in advance.One of many great things emacs has given us is the gap buffer:
http://en.wikipedia.org/wiki/Gap_buffer
To see a Java implementation of this you can look in the Java SDK source. The document model (I forget exactly what its called), used in Swing uses a gap buffer. -
Implement a program by using data structure
i've learn link-list,b-tree,red black tree,hash table. now it's time for me to implement a program using any one of these. i've no idea about how to start, and what kind of program should i write? what kind of program use data structure? i want some simple example program to make me understand. can anyone help me?
thank 4 u r time,
makiowhat sort of program do use data structure? let's say
i want to use binary search on data , how can i?As nasch said: pretty much any program uses data structures.
Okay, let's say you want to try binary search. You could do that on an array, on a singly linked list, on a doubly linked list, probably on others that I can't think of right now.
If you just want practice using the data structures you've learned, then why not write a binary search over several different ones? That will give you a feel for how they differ in usage and performance.
Or, you can just pick any kind of program that interests you. Unless it's trivially small and simple, there will probably be a use for one or more of the data strux you've learned.
A chat program needs data structures to hold curently connected users, ongoing conversations, maybe a queue for messages waiting to be sent.
A card game needs to be able to search to see if a given card is in a given hand. Needs to hold all the cards in a deck that has to be shuffled. Dealing is like popping off a stack.
A database of students and their courses might want to keep something in an ordered tree--by last name for instance.
What applications interest you? -
OC4J: marshalling does not recreate the same data structure onthe client
Hi guys,
I am trying to use OC4J as an EJB container and have come across the following problem, which looks like a bug.
I have a value object method that returns an instance of ArrayList with references to other value objects of the same class. The value objects have references to other value objects. When this structure is marshalled across the network, we expect it to be recreated as is but that does not happen and instead objects get duplicated.
Suppose we have 2 value objects: ValueObject1 and ValueObject2. ValueObject1 references ValueObject2 via its private field and the ValueObject2 references ValueObject1. Both value objects are returned by our method in an ArrayList structure. Here is how it will look like (number after @ represents an address in memory):
Object[0] = com.cramer.test.SomeVO@1
Object[0].getValueObject[0] = com.cramer.test.SomeVO@2
Object[1] = com.cramer.test.SomeVO@2
Object[1].getValueObject[0] = com.cramer.test.SomeVO@1
We would expect to see the same (except exact addresses) after marshalling. Here is what we get instead:
Object[0] = com.cramer.test.SomeVO@1
Object[0].getValueObject[0] = com.cramer.test.SomeVO@2
Object[1] = com.cramer.test.SomeVO@3
Object[1].getValueObject[0] = com.cramer.test.SomeVO@4
It can be seen that objects get unnecessarily duplicated â“ the instance of the ValueObject1 referenced by the ValueObject2 is not the same now as the instance that is referenced by the ArrayList instance.
This does not only break referential integrity, structure and consistency of the data but dramatically increases the amount of information sent across the network. The problem was discovered when we found that a relatively small but complicated structure that gets serialized into a 142kb file requires about 20Mb of network communication. All this extra info is duplicated object instances.
I have created a small test case to demonstrate the problem and let you reproduce it.
Here is RMITestBean.java:
package com.cramer.test;
import javax.ejb.EJBObject;
import java.util.*;
public interface RMITestBean extends EJBObject
public ArrayList getSomeData(int testSize) throws java.rmi.RemoteException;
public byte[] getSomeDataInBytes(int testSize) throws java.rmi.RemoteException;
Here is RMITestBeanBean.java:
package com.cramer.test;
import javax.ejb.SessionBean;
import javax.ejb.SessionContext;
import java.util.*;
public class RMITestBeanBean implements SessionBean
private SessionContext context;
SomeVO someVO;
public void ejbCreate()
someVO = new SomeVO(0);
public void ejbActivate()
public void ejbPassivate()
public void ejbRemove()
public void setSessionContext(SessionContext ctx)
this.context = ctx;
public byte[] getSomeDataInBytes(int testSize)
ArrayList someData = getSomeData(testSize);
try {
java.io.ByteArrayOutputStream byteOutputStream = new java.io.ByteArrayOutputStream();
java.io.ObjectOutputStream objectOutputStream = new java.io.ObjectOutputStream(byteOutputStream);
objectOutputStream.writeObject(someData);
objectOutputStream.flush();
System.out.println(" serialised output size: "+byteOutputStream.size());
byte[] bytes = byteOutputStream.toByteArray();
objectOutputStream.close();
byteOutputStream.close();
return bytes;
} catch (Exception e) {
System.out.println("Serialisation failed: "+e.getMessage());
return null;
public ArrayList getSomeData(int testSize)
// Create array of objects
ArrayList someData = new ArrayList();
for (int i=0; i<testSize; i++)
someData.add(new SomeVO(i));
// Interlink all the objects
for (int i=0; i<someData.size()-1; i++)
for (int j=i+1; j<someData.size(); j++)
((SomeVO)someData.get(i)).addValueObject((SomeVO)someData.get(j));
((SomeVO)someData.get(j)).addValueObject((SomeVO)someData.get(i));
// print out the data structure
System.out.println("Data:");
for (int i = 0; i<someData.size(); i++)
SomeVO tmp = (SomeVO)someData.get(i);
System.out.println("Object["+Integer.toString(i)+"] = "+tmp);
System.out.println("Object["+Integer.toString(i)+"]'s some number = "+tmp.getSomeNumber());
for (int j = 0; j<tmp.getValueObjectCount(); j++)
SomeVO tmp2 = tmp.getValueObject(j);
System.out.println(" getValueObject["+Integer.toString(j)+"] = "+tmp2);
System.out.println(" getValueObject["+Integer.toString(j)+"]'s some number = "+tmp2.getSomeNumber());
// Check the serialised size of the structure
try {
java.io.ByteArrayOutputStream byteOutputStream = new java.io.ByteArrayOutputStream();
java.io.ObjectOutputStream objectOutputStream = new java.io.ObjectOutputStream(byteOutputStream);
objectOutputStream.writeObject(someData);
objectOutputStream.flush();
System.out.println("Serialised output size: "+byteOutputStream.size());
objectOutputStream.close();
byteOutputStream.close();
} catch (Exception e) {
System.out.println("Serialisation failed: "+e.getMessage());
return someData;
Here is RMITestBeanHome:
package com.cramer.test;
import javax.ejb.EJBHome;
import java.rmi.RemoteException;
import javax.ejb.CreateException;
public interface RMITestBeanHome extends EJBHome
RMITestBean create() throws RemoteException, CreateException;
Here is ejb-jar.xml:
<?xml version = '1.0' encoding = 'windows-1252'?>
<!DOCTYPE ejb-jar PUBLIC "-//Sun Microsystems, Inc.//DTD Enterprise JavaBeans 2.0//EN" "http://java.sun.com/dtd/ejb-jar_2_0.dtd">
<ejb-jar>
<enterprise-beans>
<session>
<description>Session Bean ( Stateful )</description>
<display-name>RMITestBean</display-name>
<ejb-name>RMITestBean</ejb-name>
<home>com.cramer.test.RMITestBeanHome</home>
<remote>com.cramer.test.RMITestBean</remote>
<ejb-class>com.cramer.test.RMITestBeanBean</ejb-class>
<session-type>Stateful</session-type>
<transaction-type>Container</transaction-type>
</session>
</enterprise-beans>
</ejb-jar>
And finally the application that tests the bean:
package com.cramer.test;
import java.util.*;
import javax.rmi.*;
import javax.naming.*;
public class RMITestApplication
final static boolean HARDCODE_SERIALISATION = false;
final static int TEST_SIZE = 2;
public static void main(String[] args)
Hashtable props = new Hashtable();
props.put(Context.INITIAL_CONTEXT_FACTORY, "com.evermind.server.rmi.RMIInitialContextFactory");
props.put(Context.PROVIDER_URL, "ormi://lil8m:23792/alexei");
props.put(Context.SECURITY_PRINCIPAL, "admin");
props.put(Context.SECURITY_CREDENTIALS, "admin");
try {
// Get the JNDI initial context
InitialContext ctx = new InitialContext(props);
NamingEnumeration list = ctx.list("comp/env/ejb");
// Get a reference to the Home Object which we use to create the EJB Object
Object objJNDI = ctx.lookup("comp/env/ejb/RMITestBean");
// Now cast it to an InventoryHome object
RMITestBeanHome testBeanHome = (RMITestBeanHome)PortableRemoteObject.narrow(objJNDI,RMITestBeanHome.class);
// Create the Inventory remote interface
RMITestBean testBean = testBeanHome.create();
ArrayList someData = null;
if (!HARDCODE_SERIALISATION)
// ############################### Alternative 1 ##############################
// ## This relies on marshalling serialisation ##
someData = testBean.getSomeData(TEST_SIZE);
// ############################ End of Alternative 1 ##########################
} else
// ############################### Alternative 2 ##############################
// ## This gets a serialised byte stream and de-serialises it ##
byte[] bytes = testBean.getSomeDataInBytes(TEST_SIZE);
try {
java.io.ByteArrayInputStream byteInputStream = new java.io.ByteArrayInputStream(bytes);
java.io.ObjectInputStream objectInputStream = new java.io.ObjectInputStream(byteInputStream);
someData = (ArrayList)objectInputStream.readObject();
objectInputStream.close();
byteInputStream.close();
} catch (Exception e) {
System.out.println("Serialisation failed: "+e.getMessage());
// ############################ End of Alternative 2 ##########################
// Print out the data structure
System.out.println("Data:");
for (int i = 0; i<someData.size(); i++)
SomeVO tmp = (SomeVO)someData.get(i);
System.out.println("Object["+Integer.toString(i)+"] = "+tmp);
System.out.println("Object["+Integer.toString(i)+"]'s some number = "+tmp.getSomeNumber());
for (int j = 0; j<tmp.getValueObjectCount(); j++)
SomeVO tmp2 = tmp.getValueObject(j);
System.out.println(" getValueObject["+Integer.toString(j)+"] = "+tmp2);
System.out.println(" getValueObject["+Integer.toString(j)+"]'s some number = "+tmp2.getSomeNumber());
// Print out the size of the serialised structure
try {
java.io.ByteArrayOutputStream byteOutputStream = new java.io.ByteArrayOutputStream();
java.io.ObjectOutputStream objectOutputStream = new java.io.ObjectOutputStream(byteOutputStream);
objectOutputStream.writeObject(someData);
objectOutputStream.flush();
System.out.println("Serialised output size: "+byteOutputStream.size());
objectOutputStream.close();
byteOutputStream.close();
} catch (Exception e) {
System.out.println("Serialisation failed: "+e.getMessage());
catch(Exception ex){
ex.printStackTrace(System.out);
The parameters you might be interested in playing with are HARDCODE_SERIALISATION and TEST_SIZE defined at the beginning of RMITestApplication.java. The HARDCODE_SERIALISATION is a flag that specifies whether Java serialisation should be used to pass the data across or we should rely on OC4J marshalling. TEST_SIZE defines the size of the object graph and the ArrayList structure. The bigger this size is the more dramatic effect you get from data duplication.
The test case outputs the structure both on the server and on the client and prints out the size of the serialised structure. That gives us sufficient comparison, as both structure and its size should be the same on the client and on the server.
The test case also demonstrates that the problem is specific to OC4J. The standard Java serialisation does not suffer the same flaw. However using the standard serialisation the way I did in the test case code is generally unacceptable as it breaks the transparency benefit and complicates interfaces.
To run the test case:
1) Modify provider URL parameter value on line 15 of the RMITestApplication.java for your environment.
2) Deploy the bean to the server.
4) Run RMITestApplication on a client PC.
5) Compare the outputs on the server and on the client.
I hope someone can reproduce the problem and give their opinion, and possibly point to the solution if there is one at the moment.
Cheers,
AlexeiHi,
Eugene, wrong end user recovery. Alexey is referring to client desktop end user recovery which is entirely different.
Alexy - As noted in the previous post:
http://social.technet.microsoft.com/Forums/en-US/bc67c597-4379-4a8d-a5e0-cd4b26c85d91/dpm-2012-still-requires-put-end-users-into-local-admin-groups-for-the-purpose-of-end-user-data?forum=dataprotectionmanager
Each recovery point has users permisions tied to it, so it's not possible to retroacively give the users permissions. Implement the below and going forward all users can restore their own files.
This is a hands off solution to allow all users that use a machine to be able to restore their own files.
1) Make these two cmd files and save them in c:\temp
2) Using windows scheduler – schedule addperms.cmd to run daily – any new users that log onto the machine will automatically be able to restore their own files.
<addperms.cmd>
Cmd.exe /v /c c:\temp\addreg.cmd
<addreg.cmd>
set users=
echo Windows Registry Editor Version 5.00>c:\temp\perms.reg
echo [HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Microsoft Data Protection Manager\Agent\ClientProtection]>>c:\temp\perms.reg
FOR /F "Tokens=*" %%n IN ('dir c:\users\*. /b') do set users=!users!%Userdomain%\\%%n,
echo "ClientOwners"=^"%users%%Userdomain%\\bogususer^">>c:\temp\perms.reg
REG IMPORT c:\temp\perms.reg
Del c:\temp\perms.reg
Please remember to click “Mark as Answer” on the post that helps you, and to click “Unmark as Answer” if a marked post does not actually answer your question. This can be beneficial to other community members reading the thread. Regards, Mike J. [MSFT]
This posting is provided "AS IS" with no warranties, and confers no rights. -
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/LivingForSQLHello,
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 -
Lease Out Contract - Master Data Structural Relations
Dear Gurus,
I am new to FX RE and if my question is too simple, please excuse me!
I am researching the possibilities for the master data structure of lease in contracts and have a serious confusion.
The documentation says that objects can be assigned to a contract individually or many objects related to one contract. At the same tim it is said that rental units are assigned only to lease out contracts.
How should i proceed if my company has got many lease in contracts for different object. Is it a must the contract to be assigned to an object or it can be managed just as a contract? I saw that from the RE Navigator you can create a contract, does that mean that in FX RE the contracts itself is considered as master data record?
Any opinions will be highly appreciated.
Many thanks in advance!Dear Kumar,
Sorry if I ve been confusing. I will try to make it more clear.
I am working for a Teleco and i am researching the possibility of implementing FX - RE internally. We will not need all the functionalities of the module, but only the ones that allow you to manage your lease in contracts. We`ve got lots of base stations contracts (as you can imagine) where our company is a tenant in a lease contract.
I did some research in relation to the master data structure and cant work out how should our master data be structured. The business requirements are - handling the advance payments, accruals and postings, giving and receiving notices, adjustments of rent etc. Is it possible to create the contract within the system, set all the conditions directly in it or do we need to have another master record other that the contract itself.
My confusion comes from the fact that the standard solution of the lease outs suggests creating a rental unit first and then assigning the contract to it. But since we will be tenants we dont need to more detailed information on these objects, we just need the conditions in the contract that will let us handle all the activities that arise in connection to it.
I hope that i put the question more clearly this time.
Can you also tell me if it is possible to create a template and after entering the conditions about the particular contract to generate it from the system on a hard copy?
Many thanks and sorry if i cant make myself more clear! -
Urgent! Need help in deciding data structure to use
Hi all,
I need to implement a restaurant system by which a customer can make a reservation.
I was wondering whether vector would be able to be store such an object, The thing is I don't want a complex data structure. just sumthin simple cos i hardly have anytime left to my submission. sighz...
The thing is I need to able to search based on 2 properties of an object. Eg. I need to search for a reservation based on the customer name and the date he reserved a table.
But I am totally clueless how to search thru a vector based on 2 properties of the object... Would really appreciate some help. Like an example how to so so based on my program. Feelin so lost...This is all I have so far:
class AddReservation
static BufferedReader stdin = new BufferedReader (new InputStreamReader(System.in));
//Main Method
public static void main (String[]args)throws IOException
String custName, comments;
int covers, date, startTime, endTime;
int count = 0;
//User can only add one reservation at a time
do
//Create a new reservation
Reservation oneReservation=new Reservation();
System.out.println("Please enter customer's name:");
System.out.flush();
custName = stdin.readLine();
oneReservation.setcustName(custName);
System.out.println("Please enter number of covers:");
System.out.flush();
covers = Integer.parseInt(stdin.readLine());
oneReservation.setCovers(covers);
System.out.println("Please enter date:");
System.out.flush();
date = Integer.parseInt(stdin.readLine());
oneReservation.setDate(date);
System.out.println("Please enter start time:");
System.out.flush();
startTime = Integer.parseInt(stdin.readLine());
oneReservation.setstartTime(startTime);
System.out.println("Please enter end time:");
System.out.flush();
endTime = Integer.parseInt(stdin.readLine());
oneReservation.setendTime(endTime);
System.out.println("Please enter comments, if any:");
System.out.flush();
comments = stdin.readLine();
oneReservation.setComments(comments);
count++;
while (count<1);
class Reservation
private Reservation oneReservation;
private String custName, comments;
private int covers, startTime, endTime, date;
//Default constructor
public Reservation()
public Reservation(String custName, int covers, int date, int startTime, int endTime, String comments)
this.custName=custName;
this.covers=covers;
this.date=date;
this.startTime=startTime;
this.endTime=endTime;
this.comments=comments;
//Setter methods
public void setcustName(String custName)
this.custName=custName;
public void setCovers(int covers)
this.covers=covers;;
public void setDate(int date)
this.date=date;
public void setstartTime(int startTime)
this.startTime=startTime;
public void setendTime(int endTime)
this.endTime=endTime;
public void setComments(String comments)
this.comments=comments;
//Getter methods
public String getcustName()
return custName;
public int getCovers()
return covers;
public int getDate()
return date;
public int getstartTime()
return startTime;
public int getendTime()
return endTime;
public String getComments()
return comments;
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
class searchBooking
static BufferedReader stdin = new BufferedReader (new InputStreamReader(System.in));
public static void main (String[]args)throws IOException
int choice, date, startTime;
String custName;
//Search Menu
System.out.println("Search By: ");
System.out.println("1. Date");
System.out.println("2. Name of Customer");
System.out.println("3. Date & Name of Customer");
System.out.println("4. Date & Start time of reservation");
System.out.println("5. Date, Name of customer & Start time of reservation");
System.out.println("Please make a selection: ");
//User keys in choice
System.out.flush();
choice = Integer.parseInt(stdin.readLine());
if (choice==1)
System.out.println("Please key in Date (DDMMYY):");
System.out.flush();
date = Integer.parseInt(stdin.readLine());
else if (choice==2)
System.out.println("Please key in Name of Customer:");
System.out.flush();
custName = stdin.readLine();
else if (choice==3)
System.out.println("Please key in Date (DDMMYY):");
System.out.flush();
date = Integer.parseInt(stdin.readLine());
System.out.println("Please key in Name of Customer:");
System.out.flush();
custName = stdin.readLine();
else if (choice==4)
System.out.println("Please key in Date (DDMMYY):");
System.out.flush();
date = Integer.parseInt(stdin.readLine());
System.out.println("Please key in Start time:");
System.out.flush();
startTime = Integer.parseInt(stdin.readLine());
else if (choice==5)
System.out.println("Please key in Date (DDMMYY):");
System.out.flush();
date = Integer.parseInt(stdin.readLine());
System.out.println("Please key in Name of Customer:");
System.out.flush();
custName = stdin.readLine();
System.out.println("Please key in Start time:");
System.out.flush();
startTime = Integer.parseInt(stdin.readLine());
}Please stop calling your questions urgent. Everybody's question is urgent to them. Nobody's are urgent to the people who are going to answer them. Calling your questions urgent suggests that you think they are more important than others' (They're not.) and will only serve to irritate those who would help you. It won't get your questions answered any sooner.
-
A robust data structure for a histogram of events over time.
Hi all,
I've been thinking for days, I am still lost on how to solve the following:
Let's say that we have a list of events that occur over a certain time interval. Each event has a start timestamp and a finish timestamp. The events occur in no particular order and expand over various length of periods.
With respect to the histogram, we mark the time period of an event occuring with a frequency of one. When events overlap over a time period, we mark that time period with a frequency of number of overlapping events.
Given this raw data, we want to examine the data's frequency under various granularity such as second, minutes, hours, days, weeks, month and years for 60sec, 60min, 24 hrs, 7 days, 4 wks ranges respectively.
So, what is a good intermediate (general) data structure that can store all the various events such that they can be easily transformed to a specific granularity. My goal here is to read the event list once, and histogram of events data with respect to various timeframe can be calculated.
Does a timeline like data strucuture that stores aggregated frequencies solve my problem? With a fine granuarlity say seconds and a long time range, the data structure will bound to overflow.
Any help is greatly appreciated!
BrianYou data structure would be in terms of Classes. You need a class Anevent{
String eventName;
Date startTime;
Date endTime;
In your main program have a Vector object which can store unllimited objects and which would not overflow. Store your event objects as they happen in this Vector. After your time interval of events is completed and you have the final Vector, you can pass the vector object to various methods in your main program to be simple or pass it to specailized graph drawing classes you would have to write to draw various Histograms. -
Data structure for web-based discussion forum
Hello all. I have begun work on a discussion board forum but have not yet decided upon a data structure for the hierarchy of messages to be left on a board. Any one have any thoughts or experience in this matter? My first thought was to implement a basic linked list in which every reply to a message would be a new child of a node. This would require I use recursion in some areas for counting and finding messages but I was also thinking that this way I can store each thread object in a simple fashion using serialization.
SJTHE STANDARS DIRECTORY STRUCTURE IS :-
PROJECT FOLDER
|
|---------->WEB-INF
|------> web.xml file
|-------> classes (folder to keep java files)
|-------> lib (folder to keep jar files) -
Open ended data structure for retrieving SQL data
I have a flex project that reads data from a database and
sends it to my flex app to display in a chart. I need to do this in
Actionscript since I have to dynamically create different charts
based on the database definitions. Up til now, I have inserted the
data for each series into a separate
ArrayList(java)/ArrayCollection(flex) in this way:
BindingUtils.bindProperty(lineSeries, "dataProvider", series,
"pointList");
lineSeries.xField="point1";
lineSeries.yField="point2";
The series variable is a custom Actionscript/Java object
which contains an ArrayCollection called pointList. And the array
is made up of custom DataObjects with two fields, point1 &
point2.
But in the new paradigm, I'd basically like to create a big
array of arrays similar to a database table and then just point the
xField to one column, and the yField to another column. Anyway, it
seems like the problem is that my point1 and point2 in the current
implementation are variable names, but with this new dynamic
structure, I won't be able to create variables on the fly. So how
do I let flex know to look at column 3, for example for the yField?
The attached code is from the Flex documentation and is an example
of what I'd like to emulate (except I need to do it in
actionscript). I'd like to be able to select "month" or "amount",
etc. But coming from the Java side, there is no way for me to name
the array contained in each column.I guess I wasn't clear enough. I am actually serializing a
java object and mapping it to an actionscript object via blazeDS. I
know about how the objects translate, for example for
ArrayCollections in flex, I use ArrayLists in java. The problem is
that I'm not sure how to get the associative aspects of the arrays
in flex into my java data structures in a way that will translate
to the way flex can define arrays, such as Month:"January".
It seems that in flex, you can create an Array and assign it
an element like {month:"January", amount:"450"} and it will create
an Object with variables for month and amount. But I don't know how
to do this on the fly in Java (or in Actionscript for that matter)
when I have no way of knowing beforehand how many variables my
object will need. Each series will need an x and y, though usually
the x will be dates which are the same for each series. So if I had
10 series sharing an axis, I'd need 11 variables in my object-
date, series1, series 2...series 10. -
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 ?
AlexAlex,
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. -
Hi all,
I have a UI which may change or i may add some specific properties to the UI.
I want to have a data structure class which would be created on the basis of the properites.
Suppose employee is a UI component,then again i have to have one more UI component called department.
The class which i am using for e.g. persistence should be generated differently.
I do see reflection as one of the solution for generating the class.
edit: to generate the fields or getter,setters to be precise, as i already have the class
But is reflection is the best way,.is there any better ways to do it?
Edited by: java_jamboree on May 28, 2008 10:30 PMjava.uitl.Map and its implementations.
-
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, FrankI 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 -
what is the best data structure to use for keeping four different data
bases interconnected and updated about the changes in one another at all times while not using an existing java data structure but by implementing one by one's own?
thanx .Data structure? Coherency Protocol!
What a question anyways? If you want to implement your own, the best thing to do is to get going ...
Maybe you are looking for
-
How can one put ACLs on "content" not just objects....?
All, The security realms available in Weblogic Server only allows one to put ACL control on an "object" and not anything about putting security on the "content" that moves through that object or is accessible by that object. I wonder how people are d
-
I have always been able to remote access to my office email through VPN access. Now when I try to, a Java preference box pops up and there seems to be no way to get past it. Before, java would just load. Now it won't. I had my operating system upgrad
-
How do I delete photos from iPhoto that I imported to my library from my iPhone?
I imported a ton of pictures from my iPhone 5 to iPhoto (400+) and I want to completely delete them from iPhoto. Is there a quick, easy way to do this? I really do not want to go through my photo library and delete each individual photo, so if there
-
Prevent remote database access
we cannot change easily our passwords and we must prevent remote access to SYS and SYSTEM accounts. Is there a way to prevent remote database access on SYSTEM account without changing password ?
-
Static nonstatic class object constructor
I was wonderring what is the use of non static constructors?? we all know about static constructors, they are used for initializing the class. we all know about constructos, they are used for initializing an object from a given class. what I dont kno