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  • What is the best possible technology for pulling huge data from 4 remote servers

    - by Habib Ullah Bahar
    Hello, For one of our project, we need to pull huge real time stock data from 4 remote servers across two countries. The trivial process here, check the sources for a regular interval and save the update to database. But as these are real time stock data of more than 1000 companies, I have to pull every second, which isn't good in case of memory, bandwidth I think. Please give me suggestion on which technology/platform [We are flexible here. PHP, Python, Java, PERL - anyone of them will be OK for us] we should choose, it can be achieved easily and with better performance.

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  • How do I do automatic data serialization of data objects in Haskell

    - by Adam Gent
    One of the huge benefits in languages that have some sort of reflection/introspecition is that objects can be automatically constructed from a variety of sources. For example in Java I can use the same objects for persisting to a db (with Hibernate) serializing to XML (with JAXB) or serializing to JSON (json-lib). You can do the same in Ruby and Python also usually following some simple rules for properties or annotations for Java. Thus I don't need lots "Domain Transfer Objects". I can concentrate on the domain I am working in. It seems in very strict FP like Haskell and Ocaml this is not possible. Particularly Haskell. The only thing I have seen is doing some sort of preprocessing or meta-programming (ocaml). Is it just accepted that you have to do all the transformations from the bottom upwards? In other words you have to do lot of boring work to turn a data type in haskell into JSON/XML/DB Row object and back again into a data object.

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  • Efficient data structure for fast random access, search, insertion and deletion

    - by Leonel
    I'm looking for a data structure (or structures) that would allow me keep me an ordered list of integers, no duplicates, with indexes and values in the same range. I need four main operations to be efficient, in rough order of importance: taking the value from a given index finding the index of a given value inserting a value at a given index deleting a value at a given index Using an array I have 1 at O(1), but 2 is O(N) and insertion and deletions are expensive (O(N) as well, I believe). A Linked List has O(1) insertion and deletion (once you have the node), but 1 and 2 are O(N) thus negating the gains. I tried keeping two arrays a[index]=value and b[value]=index, which turn 1 and 2 into O(1) but turn 3 and 4 into even more costly operations. Is there a data structure better suited for this?

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  • Best data-structure to use for two ended sorted list

    - by fmark
    I need a collection data-structure that can do the following: Be sorted Allow me to quickly pop values off the front and back of the list Remain sorted after I insert a new value Allow a user-specified comparison function, as I will be storing tuples and want to sort on a particular value Thread-safety is not required Optionally allow efficient haskey() lookups (I'm happy to maintain a separate hash-table for this though) My thoughts at this stage are that I need a priority queue and a hash table, although I don't know if I can quickly pop values off both ends of a priority queue. I'm interested in performance for a moderate number of items (I would estimate less than 200,000). Another possibility is simply maintaining an OrderedDictionary and doing an insertion sort it every-time I add more data to it. Furthermore, are there any particular implementations in Python. I would really like to avoid writing this code myself.

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  • getting core file

    - by ashwani66476
    Hello All I am running a Core JAVA application on AIX machine, and it creates a file named "core". My concern are 1. I am not able to open this "core" file in "Heap Analyzer" or "Thread Analyzer". 2. Which tools do I need to use, So that I can analyze this "core" file. 3. Could any one elaborate more about this file? why this "core" file creates. Waiting for response..... Many Thanks

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  • Storing a bucket of numbers in an efficient data structure

    - by BlitzKrieg
    I have a buckets of numbers e.g. - 1 to 4, 5 to 15, 16 to 21, 22 to 34,.... I have roughly 600,000 such buckets. The range of numbers that fall in each of the bucket varies. I need to store these buckets in a suitable data structure so that the lookups for a number is as fast as possible. So my question is what is the suitable data structure and a sorting mechanism for this type of problem. Thanks in advance

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  • Queue-like data structure with fast search and insertion

    - by Max
    I need a datastructure with the following properties: It contains integer numbers, no duplicates. After it reaches the maximal size the first element is removed. So if the capacity is 3, then this is how it would look when putting in it sequential numbers: {}, {1}, {1, 2}, {1, 2, 3}, {2, 3, 4}, {3, 4, 5} etc. Only two operations are needed: inserting a number into this container (INSERT) and checking if the number is already in the container (EXISTS). The number of EXISTS operations is expected to be approximately 2 * number of INSERT operations. I need these operations to be as fast as possible. What would be the fastest data structure or combination of data structures for this scenario?

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  • Data Structure for a particular problem??

    - by AGeek
    Hi, Which data structure can perform insertion, deletion and searching operation in O(1) time in the worst case. We may assume the set of elements are integers drawn from a finite set 1,2,...,n, and initialization can take O(n) time. I can only think of implementing a hash table. Implementing it with Trees will not give O(1) time complexity for any of the operation. Or is it possible?? Kindly share your views on this, or any other data structure apart from these.. Thanks..

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  • Transferring Data Between Server and Client (Mobile)

    - by Byron
    Scenario: Client (Mobile) - .Net CF 2.0, SQL CE 3.0 Server - .Net 2.0, SQL Server 2005, Web Service Client and Server database schemas differ. From server - only certain columns from certain tables need to be synced. From client - everything will need to be synced once client has made changes. Client will continually poll a web service to download and upload data. A framework will be developed to package and unpackage data, used by both client and server. How would you develop the packaging and unpackaging? Use datasets, serialise strongly typed objects? All suggestions welcome. Thanks

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  • How do I stack images to simulate depth using Core Animation?

    - by Jeffrey Berthiaume
    I have a series of UIImages with which I need to simulate depth. I can't use scaling because I need to be able to rotate the parent view, and the images should look like they're stacked visibly in front of each other, not on the same plane. I made a new ViewController-based project and put this in the viewDidLoad (as well as attached three 120x120 pixel images named 1.png, 2.png, and 3.png): - (void)viewDidLoad { // display image 3 UIImageView *three = [[UIImageView alloc] initWithImage:[UIImage imageNamed:@"3.png"]]; three.center = CGPointMake(160 + 60, 240 - 60); [self.view addSubview:three]; // rotate image 3 around the z axis // THIS IS INCORRECT CATransform3D theTransform = three.layer.transform; theTransform.m34 = 1.0 / -1000; three.layer.transform = theTransform; // display image 2 UIImageView *two = [[UIImageView alloc] initWithImage:[UIImage imageNamed:@"2.png"]]; two.center = CGPointMake(160, 240); [self.view addSubview:two]; // display image 1 UIImageView *one = [[UIImageView alloc] initWithImage:[UIImage imageNamed:@"1.png"]]; one.center = CGPointMake(160 - 60, 240 + 60); [self.view addSubview:one]; // rotate image 3 around the z axis // THIS IS INCORRECT theTransform = one.layer.transform; theTransform.m34 = 1.0 / 1000; one.layer.transform = theTransform; // release the images [one release]; [two release]; [three release]; // rotate the parent view around the y axis theTransform = self.view.layer.transform; theTransform.m14 = 1.0 / -500; self.view.layer.transform = theTransform; [super viewDidLoad]; } I have very specific reasons why I'm not using an EAGLView and why I'm not loading the images as CALayers (i.e. why I'm using UIImageViews for each one). This is just a quick demo that I can use to work out exactly what I need in my parent application. Is there some matrix way to translate these 2d images along the z-axis so they will look like what I'm trying to represent? I've gone through the other StackOverflow articles as well as the Wikipedia references, and have not found what I'm looking for -- although I might not necessarily be using the right terms for what I'm trying to do.

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  • How does a custom accessor method implementation in Core Data look like?

    - by dontWatchMyProfile
    The documentation is pretty confusing on this one: The implementation of accessor methods you write for subclasses of NSManagedObject is typically different from those you write for other classes. If you do not provide custom instance variables, you retrieve property values from and save values into the internal store using primitive accessor methods. You must ensure that you invoke the relevant access and change notification methods (willAccessValueForKey:, didAccessValueForKey:, willChangeValueForKey:, didChangeValueForKey:, willChangeValueForKey:withSetMutation:usingObjects:, and didChangeValueForKey:withSetMutation:usingObjects:). NSManagedObject disables automatic key-value observing (KVO, see Key-Value Observing Programming Guide) change notifications, and the primitive accessor methods do not invoke the access and change notification methods. In accessor methods for properties that are not defined in the entity model, you can either enable automatic change notifications or invoke the appropriate change notification methods. Are there any examples that show how these look like?

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  • How to wait until location is completely found? (Core Location)

    - by sudo rm -rf
    Hello. I have a problem within my app. I'm trying to find the user's location to the best preciseness in order to determine their zip-code. Currently I have a button that, when pressed, starts a method named locateMe. -(IBAction)locateMe; { self.locationManager = [[CLLocationManager alloc] init]; locationManager.delegate = self; locationManager.desiredAccuracy = kCLLocationAccuracyBest; [locationManager startUpdatingLocation]; Then I've implemented didUpdateToLocation: -(void)locationManager:(CLLocationManager *)manager didUpdateToLocation:(CLLocation *)newLocation fromLocation:(CLLocation *)oldLocation; { NSLog(@"Found location! %f,%f",newLocation.coordinate.latitude,newLocation.coordinate.longitude); } I had previously done much more complicated stuff in didUpdateToLocation but as I tested some things I realized that the first location it found was not precise in the least. So, I put the NSLog call in there and it gave me an output similar to below... Found location! 39.594093,-98.614834 Found location! 39.601372,-98.592171 Found location! 39.601372,-98.592171 Found location! 39.611444,-98.538196 Found location! 39.611444,-98.538196 As you can see, it first gives me a value which is not correct, which was causing problems within my app because it wasn't giving the correct location. So, here's my question. Is there any way I can wait for the location manager to finish finding the most precise location? Thanks in advance! EDIT: I'm wanting something like this: if (newLocation.horizontalAccuracy <= locationManager.desiredAccuracy) { } But it never gets called!

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  • AutoComplete implementation - Interview Question

    - by user181218
    Hi, Say you have a DB table with two cols: SearchPhrase(String) | Popularity(Int). You need to initialize a DS so that you could use it to implement an autocomplete feature (like google suggest) comfortably. The requirement: Once the data from the db is processed into the data structure, when you type a letter you get the 10 most popular searchphrases from the db starting with that letter,then when you type the next one you get the 10 .... with these two letters and so on. The question only concerns planning the ds and pseudocoding Insert,Search etc. Note: YOU CANNOT USE TRIE DS. Any ideas?

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  • ADO.NET Data Service -- non .NET consumers

    - by SwampyFox
    Has anyone come across an example of a non .Net consumer of an ADO.NET Data Service? I am on the second day of looking at what Astoria is and how it can be used. I am also trying to answer why would I use this instead of a web service? After getting my examples running, I kind get the RESTful approach to getting data out the system. And, plugging it into a .net client is incredibly easy. But, then I wondered how a non-.NET consumer would go about it. Any ideas (pointers) definitely appreciated...

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  • Best way to collect and store data daily?

    - by mktb
    I have a bunch of statistics: # of users, # of families, ratio user/family, etc. I'd like to store these daily so I can view this data historically. However, I'm looking for the most effective way to store this data. Should I run a cron job that writes to the database DATE: today USERS: 123 FAMILIES: 456 RATIO: 7.89 or whatever? (or should I write multiple rows like DATE: today DATATYPE: users VALUE: 123?) Or is there another option I can use that is more efficient or more effective? Thanks!

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  • Data Warehouse: One Database or many?

    - by drrollins
    At my new company, they keep all data associated with the data warehouse, including import, staging, audit, dimension and fact tables, together in the same physical database. I've been a database developer for a number of years now and this consolidation of function and form seems counter to everything I know. It seems to make security, backup/restore and performance management issues more manually intensive. Is this something that is done in the industry? Are there substantial reasons for doing or not doing it? The platform is Netezza. The size is in terabytes, hundreds of millions of rows. What I'm looking to get from answers to this question is a solid understanding of how right or wrong this path is. From your experience, what are the issues I should be focused on arguing if this is a path that will cause trouble for us down the road. If it is no big deal, then I'd like to know that as well.

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  • How to intercept deallocate callbacks of Core Foundation objects in Objective-C.

    - by Matteo
    I'm writing an Eiffel wrapper for AppKit and Foundation and I need to hijack all -dealloc methods. Thanks to the dynamic nature of Objective-C it is pretty easy to do that. But the problem is it only works with some of the Foundation or AppKit objects. There are certain objects (e.g. NSString, NSArray, NSDate, ...) that are actually CF objects so the dealloc method doesn't get called. Instead the deallocate callbacks of the allocator that allocated the CF object is called. Is there a way to intercept that?

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  • Better data-structure design

    - by Tempname
    Currently in my application I have a single table that is giving me a bit of trouble. The issue at hand is I have a value object that is mapped to this table. When the data is returned to me as an array of value objects, I have to then loop through this array and begin my recursion by matching the ParentID to parent ObjectID's. The column ParentID is either null (acts a parent) or it holds the value of an ObjectID. I know there has to be a better way to create this data structure so that I do not have to do recursive loops to match ParentID's with their ObjectID's. Any help with this is greatly appreciated. Here is the table in describe form: +----------------+------------------+------+-----+---------------------+-----------------------------+ | Field | Type | Null | Key | Default | Extra | +----------------+------------------+------+-----+---------------------+-----------------------------+ | ObjectID | int(11) unsigned | NO | PRI | NULL | auto_increment | | ObjectHeight | decimal(6,2) | NO | | NULL | | | ObjectWidth | decimal(6,2) | NO | | NULL | | | ObjectX | decimal(6,2) | NO | | NULL | | | ObjectY | decimal(6,2) | NO | | NULL | | | ObjectLabel | varchar(255) | NO | | NULL | | | TemplateID | int(11) unsigned | NO | MUL | NULL | | | ObjectTypeID | int(11) unsigned | NO | MUL | NULL | | | ParentID | int(11) unsigned | YES | MUL | NULL | | | CreationDate | datetime | YES | | 0000-00-00 00:00:00 | | | LastModifyDate | timestamp | YES | | NULL | on update CURRENT_TIMESTAMP | +----------------+------------------+------+-----+---------------------+-----------------------------+e

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  • How to calculate the audio file duration in core audio?

    - by mystify
    I have this info variable which is of this type: struct AudioStreamBasicDescription { Float64 mSampleRate; UInt32 mFormatID; UInt32 mFormatFlags; UInt32 mBytesPerPacket; UInt32 mFramesPerPacket; UInt32 mBytesPerFrame; UInt32 mChannelsPerFrame; UInt32 mBitsPerChannel; UInt32 mReserved; }; How could I calculate the total duration of the audio file, in seconds?

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  • Just an experiment changing the application data path

    - by Arthur
    When I change the Appication Data path in windows xp registry to a network folder I get this error message on the next system startup: "windows cannot load the user's profile but has logged you with the default profile system" The registry keys are: "[HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\Shell Folders]" "[HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\User Shell Folders]" under the names "AppData" and "Local AppData" I dont care if "Windows logins you with the default profile system" but is there a way to disable that message, or change the message timeout form 30 seconds to 0?,or maybe create an script that changes the Application Data path every system startup? P.S. The computer with the shared folder is always on.

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  • Adding a column to a data.frame

    - by Susanne Dreisigacker
    I have the data.frame below. I want to add a column that classifies my data according to column 1 (h_no) in that way that the first series of h_no 1,2,3,4 is class 1, the second series of h_no (1 to 7) is class 2 etc. such as indicated in the last column. h_no h_freq h_freqsq 1 0.09091 0.008264628 1 2 0.00000 0.000000000 1 3 0.04545 0.002065702 1 4 0.00000 0.000000000 1 1 0.13636 0.018594050 2 2 0.00000 0.000000000 2 3 0.00000 0.000000000 2 4 0.04545 0.002065702 2 5 0.31818 0.101238512 2 6 0.00000 0.000000000 2 7 0.50000 0.250000000 2 1 0.13636 0.018594050 3 2 0.09091 0.008264628 3 3 0.40909 0.167354628 3 4 0.04545 0.002065702 3

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  • When does the DENY delete rule in Core Data actually deny deletion of an object?

    - by dontWatchMyProfile
    An Employee has an inverse relationship to it's Department and vice versa. The Employee entity has an Relationship called department, and it has a DENY delete rule. Employee shall be deleted. Now: Does DENY actually deny deletion of employee, because department is still referencing a Department? Or does it mean that a Department can't be deleted because an Employee is referencing it?

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  • Couldn't I just pass an copied string to an Core Data property?

    - by dontWatchMyProfile
    The docs say: The default implementation does not copy attribute values. If the attribute value may be mutable and implements the NSCopying protocol (as is the case with NSString, for example), you can copy the value in a custom accessor to help preserve encapsulation (for example, in the case where an instance of NSMutableString is passed as a value). So instead of getting into trouble and inconvenience with overwriting accessors in my NSManagedObject subclass, couldn't I simply do something like this? myManagedObject.firstName = [[firstNameMutableStr copy] autorelease]; This would have the exact same effect, or not? The dynamic implementation would retain that anyways ... so.... why not the easy way?

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