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  • sequentially-consistent atomic load on x86

    - by axe
    Hello all, I'm interested in sequentially-consistent load operation on x86. As far as I see from assembler listing, generated by compiler it is implemented as a plain load on x86, however plain loads as far as I know guaranteed to have acquire semantics, while plain stores are guaranteed to have release. Sequentially-consistent store is implemented as locked xchg, while load as plain load. That sounds strange to me, could you please explain this in details? added Just found in internet, that sequentially-consistent atomic load could be done as simple mov as long as store is done with locked xchg, but there was no prove and no links to documentation. Do you know where can I read about that? Thanks in advance.

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  • Database design advice needed.

    - by user346271
    Hi all, I'm a lone developer for a telecoms company, and am after some database design advice from anyone with a bit of time to answer. I am inserting into one table ~2 million rows each day, these tables then get archived and compressed on a monthly basis. Each monthly table contains ~15,000,000 rows. Although this is increasing month on month. For every insert I do above I am combining the data from rows which belong together and creating another "correlated" table. This table is currently not being archived, as I need to make sure I never miss an update to the correlated table. (Hope that makes sense) Although in general this information should remain fairly static after a couple of days of processing. All of the above is working perfectly. However my company now wishes to perform some stats against this data, and these tables are getting too large to provide the results in what would be deemed a reasonable time. Even with the appropriate indexes set. So I guess after all the above my question is quite simple. Should I write a script which groups the data from my correlated table into smaller tables. Or should I store the queries result sets in something like memcache? I'm already using mysqls cache, but due to having limited control over how long the data is stored for, it's not working ideally. The main advantages I can see of using something like memcache: No blocking on my correlated table after the query has been cashed. Greater flexibility of sharing the collected data between the backend collector and front end processor. (i.e custom reports could be written in the backend and the results of these stored in the cache under a key which then gets shared with anyone who would want to see the data of this report) Redundancy and scalability if we start sharing this data with a large amount of customers. The main disadvantages I can see of using something like memcache: Data is not persistent if machine is rebooted / cache is flushed. The main advantages of using MySql Persistent data. Less code changes (although adding something like memcache is trivial anyway) The main disadvantages of using MySql Have to define table templates every time I want to store provide a new set of grouped data. Have to write a program which loops through the correlated data and fills these new tables. Potentially will still grow slower as the data continues to be filled. Apologies for quite a long question. It's helped me to write down these thoughts here anyway, and any advice/help/experience with dealing with this sort of problem would be greatly appreciated. Many thanks. Alan

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  • Fail to save a managed object to core-data after its properties were updated.

    - by Tzur Gazit
    I have to trouble to create the object, but updating it fails. Here is the creation code: // Save data from pList to core data fro the first time - (void) saveToCoreData:(NSDictionary *)plistDictionary { // Create system parameter entity SystemParameters *systemParametersEntity = (SystemParameters *)[NSEntityDescription insertNewObjectForEntityForName:@"SystemParameters" inManagedObjectContext:mManagedObjectContext]; //// // GPS SIMULATOR //// NSDictionary *GpsSimulator = [plistDictionary valueForKey:@"GpsSimulator"]; [systemParametersEntity setMGpsSimulatorEnabled:[[GpsSimulator objectForKey:@"Enabled"] boolValue]]; [systemParametersEntity setMGpsSimulatorFileName:[GpsSimulator valueForKey:@"FileName"]]; [systemParametersEntity setMGpsSimulatorPlaybackSpeed:[[GpsSimulator objectForKey:@"PlaybackSpeed"] intValue]]; [self saveAction]; } During execution the cached copy is changed and then it is saved (or trying) to the database. Here is the code to save the changed copy: // Save data from pList to core data fro the first time - (void) saveSystemParametersToCoreData:(SystemParameters *)theSystemParameters { // Step 1: Select Data NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init]; NSEntityDescription *entity = [NSEntityDescription entityForName:@"SystemParameters" inManagedObjectContext:mManagedObjectContext]; [fetchRequest setEntity:entity]; NSError *error = nil; NSArray *items = [self.managedObjectContext executeFetchRequest:fetchRequest error:&error]; [fetchRequest release]; if (error) { NSLog(@"CoreData: saveSystemParametersToCoreData: Unresolved error %@, %@", error, [error userInfo]); abort(); } // Step 2: Update Object SystemParameters *systemParameters = [items objectAtIndex:0]; //// // GPS SIMULATOR //// [systemParameters setMGpsSimulatorEnabled:[theSystemParameters mGpsSimulatorEnabled]]; [systemParameters setMGpsSimulatorFileName:[theSystemParameters mGpsSimulatorFileName]]; [systemParameters setMGpsSimulatorPlaybackSpeed:[theSystemParameters mGpsSimulatorPlaybackSpeed]]; // Step 3: Save Updates [self saveAction]; } As to can see, I fetch the object that I want to update, change its values and save. Here is the saving code: - (void)saveAction { NSError *error; if (![[self mManagedObjectContext] save:&error]) { NSLog(@"ERROR:saveAction. Unresolved Core Data Save error %@, %@", error, [error userInfo]); exit(-1); } } The Persistent store method: - (NSPersistentStoreCoordinator *)persistentStoreCoordinator { if (mPersistentStoreCoordinator != nil) { return mPersistentStoreCoordinator; } NSString *path = [self databasePath]; NSURL *storeUrl = [NSURL fileURLWithPath:path]; NSError *error = nil; mPersistentStoreCoordinator = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:[self managedObjectModel]]; if (![mPersistentStoreCoordinator addPersistentStoreWithType:NSSQLiteStoreType configuration:nil URL:storeUrl options:nil error:&error]) { NSLog(@"Unresolved error %@, %@", error, [error userInfo]); abort(); } return mPersistentStoreCoordinator; } There is no error but the sqLite file is not updated, hence the data is not persistent. Thanks in advance.

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  • Is there a comprehensive list of the NHibernate event listeners and when they actually fire?

    - by snicker
    So I am looking for a nice list of NHibernate events that actually describes when they are fired, in a typical scenario. IE something like PreUpdateEventListener - Fires when an object that is already persistent is changing I currently just rifle through the source and try to figure it out, but it's kinda painful, and I figure that someone must have done this already at some point.

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  • Core Data strategy using in memory cache, or no core data at all?

    - by randombits
    I have a user interface where the user can check off a bunch of items from a tableview, almost like a todo list. The items are populated from a Core Data stack. I need to be able to take all of the items they're clicking through and put them into a "temporary" shopping cart. Once they're in the shopping cart, users can go through the list and remove the items, or just submit them to a server. The thing is, the selected items are temporary just like an internet based shopping cart. It's nothing something that gets persisted once the application closes. Once the view is no longer in display, I can assume that the shopping cart is safe to discard. What's the best way to approach this? Since the user is essentially clicking on instances that map back to a Core Data entity .. should I setup a different persistence store such as in memory and add that store to my managed object context?

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  • Options for storing large text blobs in/with an SQL database?

    - by kdt
    Hi, I have some large volumes of text (log files) which may be very large (up to gigabytes). They are associated with entities which I'm storing in a database, and I'm trying to figure out whether I should store them within the SQL database, or in external files. It seems like in-database storage may be limited to 4GB for LONGTEXT fields in MySQL, and presumably other DBs have similar limits. Also, storing in the database presumably precludes any kind of seeking when viewing this data -- I'd have to load the full length of the data to render any part of it, right? So it seems like I'm leaning towards storing this data out-of-DB: are my misgivings about storing large blobs in the database valid, and if I'm going to store them out of the database then are there any frameworks/libraries to help with that? (I'm working in python but am interested in technologies in other languages too)

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  • Code to generate random numbers in C++

    - by user1678927
    Basically I have to write a program to generate random numbers to simulate the rolling of a pair of dice. This program should be constructed in multiple files. The main function should be in one file, the other functions should be in a second source file, and their prototypes should be in a header file. First I write a short function that returns a random value between 1 and 6 to simulate the rolling of a single 6-sided die.Second, i write a function that pretends to roll a pair of dice by calling this function twice. My program starts by asking the user how many rolls should be made. Then I write a function to simulate rolling the dice this many times, keeping a count of exactly how many times the values 2,3,4,5,6,7,8,9,10,11,12(each number is the sum of a pair of dice) occur in an array. Later I write a function to display a small bar chart using these counts that ideally would look something like below for a sample of 144 rolls, where the number of asterisks printed corresponds to the count: 2 3 4 5 6 7 8 9 10 11 12 * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * Next, to see how well the random number generator is doing, I write a function to compute the average value rolled. Compare this to the ideal average of 7. Also, print out a small table showing the counts of each roll made by the program, the ideal count based on the frequencies above given the total number of rolls, and the difference between these values in separate columns. This is my incomplete code so far: "Compiler visual studio 2010" int rolling(){ //Function that returns a random value between 1 and 6 rand(unsigned(time(NULL))); int dice = 1 + (rand() %6); return dice; } int roll_dice(int num1,int num2){ //it calls 'rolling function' twice int result1,result2; num1 = rolling(); num2 = rolling(); result1 = num1; result2 = num2; return result1,result2; } int main(void){ int times,i,sum,n1,n2; int c1,c2,c3,c4,c5,c6,c7,c8,c9,c10,c11;//counters for each sum printf("Please enter how many times you want to roll the dice.\n") scanf_s("%i",&times); I pretend to use counters to count each sum and store the number(the count) in an array. I know i need a loop (for) and some conditional statements (if) but m main problem is to get the values from roll_dice and store them in n1 and n2 so then i can sum them up and store the sum in 'sum'.

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  • Problem storing string containing quotes

    - by Jack
    I have the following table - $sql = "CREATE TABLE received_queries ( sender_screen_name varchar(50), text varchar(150) )"; I use the following SQL statement to store values in the table $sql = "INSERT INTO received_queries VALUES ('$sender_screen_name', '$text')"; Now I am trying to store the following string as 'text'. One more #haiku: Cotton wool in mind; feeling like a sleep won't cure; I need some coffee. and I get the following error message Error: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 't cure; I need some coffee.')' at line 1 I think must be a pretty common problem. How do I solve it?

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  • ext-js update params dynamically

    - by jeffkolez
    I'm building a search using ext-js. I have an event that fires on keyup. I want to be able to change either the URL I'm searching, or the params. I've had luck with neither. Here's my snippit of code: Ext.get("search").on('keyup', function() { proxy.url = '/customer/list?key=' + $('search').value; store.load(); }); But, no love for me. The store loads, but the proxy.url is the old value. Is what I'm trying to do possible? Thanks in advance!

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  • fetch some data from two tables

    - by user1753971
    i have site like imdb and we provide movie information sin site..and our website have option to rate all movies for every users. I have two tables 1 . imdb (its for store movie details) id,name,actors,vote 2. ratings (its for store users rating details) id,rating_id(its same as id from first table),rating_num,IP now what am doing is..when anyone rating a movie take the avg of that movie rating by using rating tables (total ratings/number of ratings) and insert that value into "vote" column in first table..my demands this..thats why done like this.. Now my problem is..i want to fetch top rated movies..i mean in vote column which movie have top rating which want to list and one more condition is that that movie should rated by 10 users(use ratings table for that) thanks in advance

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  • iPhone CoreData Migration and modifying data

    - by ScottL
    I have an app that has both static data and user entered data in the CoreData store. I understand how to do a lightweight migration to a new database version, but how to I add or modify the static data without affecting the users data? If I have 50 static data entries to add and a couple to modify (ie. spelling mistakes) should they be stored in a different sqlite db and copied over? Also, is it possible to look at the version of the data store so that this copy only happens the first time the app is started up after upgrading? Sorry for the general noob type question, but this is the first time I have ever had to deal with this sort of issue. Thanks, Scott

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  • Multiple key map in c++

    - by Morgan
    Hi, I'm wondering if any of you know of a c++ associative map container type which I can perform multiple key lookups on. The map needs to have constant time lookups but I don't care if it's ordered or unordered. It just needs to be fast. For example, I want to store a bunch of std::vector objects in a map with an integer and a void* as the lookup keys. Both the int and the void* must match for my vector to be retrieved. Does anything like this exist already? Or am I going to have to roll my own. If so, any suggestions? I've been trying to store a boost::unordered_map inside another boost::unordered_map, but I have not had any success with this method yet. Maybe I will continue Pershing this method if there is no simpler way. Thanks!

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  • Storing PDFs in MS Access Database using Forms

    - by Matthew Jones
    I need to store PDF files in an Access database on a shared drive using a form. I figured out how to do this in tables (using the OLE Object field, then just drag-and-drop) but I would like to do this on a Form that has a Save button. Clicking the save button would store the file (not just a link) in the database. Any ideas on how to do this? EDIT: I am using Access 2003, and the DB will be stored on a share drive, so I'm not sure linking to the files will solve the problem.

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  • How to dynamically load and switch the resource file in the web app (ASP.NET) without recompiling ?

    - by Thomas Wanner
    I would like to store the resource files (containing texts for labels etc.) for my web application in the database to be able to edit and create them dynamically later (probably in the UI). My idea was to store the whole resx file in an xml column and simply load it on demand - depending on the language and some other attributes of the current user when he is logging into the application or switching the context. The important thing is that the resources do not only depend on the culture info of the user but also on some context information that can be switched by user without logging off and on again (in our case called "group", not having anything to do with a group of users). Is it possible somehow to load the contents of the resources from an external source and simply switch them without web application being recompiled by the server ? I know that there are some interfaces on which I could hook up and implement a custom resources provider which reads from the database directly but if it could work somehow with the resx files it would probably make things a lot easier..

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  • WCF. Robust big file transfer.

    - by Sharov
    Hello everybody! I want to transfer big files (1GB) over unreliable transport channels. When connection is interrupted, I don't want start file transfering from the begining. I can partially store it in a temp table and store last readed position, so when connection is reestablished I can request continue uploading of file from this position. Is there any best-practice for such kind of things. I'm currently use chunking channel. Thanks in advance.

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  • @Unique doesn't have any effect in DataNucleus w/ NeoDatis

    - by David Parks
    Using JDO / DataNucleus / NeoDatis datastore I added @Unique to a field of a persistable object, however I am allowed to create multiple objects which violate the unique constraint. The docs for DataNucleus/NeoDatis suggest that Unique fields are supported. @PersistenceCapable public class User { @Persistent @Unique private String username; //... } If I add multiple objects to the DB with the same username there's no problem doing so. :(

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  • Storing user settings in table - how?

    - by Mdillion
    I have settings for the user about 200 settings, these include notice settings and tracing settings from user activities on objects. The problem is how to store it in the DB? Should each setting be a row or a column? If colunm then table will have 200 colunms. If row then about 3 colunms but 200 rows per user x even 10 million users = not good. So how else can i store all these settings? NOTE: these settings are a mix of text entry and FK lookups to other tables. Thanks.

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  • How to restrict the range of elements of C++ STL vector?

    - by cambr
    vector<int> l; for(int i=0;i<10;i++){ l.push_back(i); } I want the vector to only be able to store numbers from a specified range (or set). How can that be done, in general? In particular, I want to restrict the vector to beonly be able to store single digits. So, if I do a l[9]++, it should give me an error or warn me. (because 10 is not a single digit number). Similarly, l[0]-- should warn me. Is there a way to do this using C++ STL vector?

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  • disable download of my paid app in Android

    - by Boy
    I have a paid app in the store which will remove the ads in another app when it is installed on that device. Now I want to remove this 'remove ads' app, as I want to have an in-app payement for this for instance (or maybe I just keep the ads version only). But the problem is, if I unpublish the app, people who bought it will not be able to download it again when they get a new phone or reset their phone. How to I keep the app in the Play Store, but prevent people from buying it? Is this possible? My backup plan is: make the app cost 10.000 euro's and put in the message that this app should not be bought anymore. But I don't like that...

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  • Can I use Google Maps API (Places API) in my iPhone app to find locations near me?

    - by Mark
    I have a couple of questions regarding using Google maps API, especially the Places API in my iPhone application. Can I use Places API in my iPhone app and still release the app as a paid app? Could I release my app as free if I am unable to use these APIs in a paid app? Is there an example for figuring out store locations around user's current location using Places API? For example if the user types "Groceries" in the app, I would like to show all the Store that sell groceries near the user's location. Thanks!

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  • Storing dates i Train schedule MYSQL

    - by App_beginner
    Hi I have created a train schedule database in MYSQL. There are several thousand routes for each day. But with a few exceptions most of the routes are similar for every working day, but differ on weekends. At this time I basically update my SQL tables at midnight each day, to get the departures for the next 24 hours. This is however very inconvenient. So I need a way to store dates in my tables so I don't have to do this every day. I tried to create a separate table where I stored dates for each routenumber (routenumbers are resetted each day), but this made my query so slow that it was impossible to use. Does this mean I would have to store my departure and arrival times as datetimes? In that case the main table containing routes would have several million entries. Or is there another way? My routetable looks like this: StnCode (referenced in seperate Station table) DepTime ArrTime Routenumber legNumber

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