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  • SQL Databases and table design/organization

    - by John McMullen
    (NOOB disclaimer) I'm working on a system (a type of map), that is accessed mostly via 3 fields: ID (auto incremented), X coordinate, and Y coordinate. As it is right now, i have all data on the map, stored in 1 table. Whenever the map display is loaded it simply queries the database for contents in x and y, and the DB gives the data (other fields in the same entry). If an item on the map is doing something, it has a flag saying its doing something, and then has an ID of the action in another table holding that type of 'actions'. Essentially, for all map data, its stored in 1 table. All actions of a certain type are stored in their own table. I'm a noob, and i'm wondering what the most effective/efficient structure for such a design? (a map that has items, and each item has stats/actions). I'm using PHP atm, using standard SQL queries to get my data. Should i split up the tables so that there are only x number of entries on a table? (coord range limits)? Should it just keep growing and growing? There's a lot of queries to the table... so just tryin to see what is best :/

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  • Real time embeddable http server library required

    - by Howard May
    Having looked at several available http server libraries I have not yet found what I am looking for and am sure I can't be the first to have this set of requirements. I need a library which presents an API which is 'pipelined'. Pipelining is used to describe an HTTP feature where multiple HTTP requests can be sent across a TCP link at a time without waiting for a response. I want a similar feature on the library API where my application can receive all of those request without having to send a response (I will respond but want the ability to process multiple requests at a time to reduce the impact of internal latency). So the web server library will need to support the following flow 1) HTTP Client transmits http request 1 2) HTTP Client transmits http request 2 ... 3) Web Server Library receives request 1 and passes it to My Web Server App 4) My Web Server App receives request 1 and dispatches it to My System 5) Web Server receives request 2 and passes it to My Web Server App 6) My Web Server App receives request 2 and dispatches it to My System 7) My Web Server App receives response to request 1 from My System and passes it to Web Server 8) Web Server transmits HTTP response 1 to HTTP Client 9) My Web Server App receives response to request 2 from My System and passes it to Web Server 10) Web Server transmits HTTP response 2 to HTTP Client Hopefully this illustrates my requirement. There are two key points to recognise. Responses to the Web Server Library are asynchronous and there may be several HTTP requests passed to My Web Server App with responses outstanding. Additional requirements are Embeddable into an existing 'C' application Small footprint; I don't need all the functionality available in Apache etc. Efficient; will need to support thousands of requests a second Allows asynchronous responses to requests; their is a small latency to responses and given the required request throughput a synchronous architecture is not going to work for me. Support persistent TCP connections Support use with Server-Push Comet connections Open Source / GPL support for HTTPS Portable across linux, windows; preferably more. I will be very grateful for any recommendation Best Regards

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  • Right way to return proxy model instance from a base model instance in Django ?

    - by sotangochips
    Say I have models: class Animal(models.Model): type = models.CharField(max_length=255) class Dog(Animal): def make_sound(self): print "Woof!" class Meta: proxy = True class Cat(Animal): def make_sound(self): print "Meow!" class Meta: proxy = True Let's say I want to do: animals = Animal.objects.all() for animal in animals: animal.make_sound() I want to get back a series of Woofs and Meows. Clearly, I could just define a make_sound in the original model that forks based on animal_type, but then every time I add a new animal type (imagine they're in different apps), I'd have to go in and edit that make_sound function. I'd rather just define proxy models and have them define the behavior themselves. From what I can tell, there's no way of returning mixed Cat or Dog instances, but I figured maybe I could define a "get_proxy_model" method on the main class that returns a cat or a dog model. Surely you could do this, and pass something like the primary key and then just do Cat.objects.get(pk = passed_in_primary_key). But that'd mean doing an extra query for data you already have which seems redundant. Is there any way to turn an animal into a cat or a dog instance in an efficient way? What's the right way to do what I want to achieve?

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  • one table is shared between several websites

    - by sami
    I have a static table that's shared by several websites. By static, I mean that the data is read but never updated by the websites. Currently, all websites are served from the same server but that may change. I want to minimize the need for creating/maintaining this table for each of the websites, so I thought about turning it to an xml file that's stored in a shared library that all websites have access to. The problem is I use an ORM and use forign key constraints to ensure integrity of the ids used from that table, so by removing that table out of the MySQL database into an XML file, will this affect the integrity of the ids coming from that table? My table looks like this <table name="entry"> <column name="id" type="INTEGER" primaryKey="true" autoIncrement="true" /> <column name="title" type="VARCHAR" size="500" required="true" /> </table> and I use it as a foreign key in other tables <table name="refer"> <column name="id" type="INTEGER" primaryKey="true" autoIncrement="true" /> <column name="linkto" type="INTEGER"/> <foreign-key foreignTable="entry"> <reference local="linkto" foreign="id" /> </foreign-key> </table> So I'm wondering if I remove that table out of the database, is there a way to retain that referential integrity? And of course are these any other efficient ways to do the same thing? I just don't want to have to repeat that table for several websites.

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  • SQL Server 2008 - Keyword search using table Join

    - by Aaron Wagner
    Ok, I created a Stored Procedure that, among other things, is searching 5 columns for a particular keyword. To accomplish this, I have the keywords parameter being split out by a function and returned as a table. Then I do a Left Join on that table, using a LIKE constraint. So, I had this working beautifully, and then all of the sudden it stops working. Now it is returning every row, instead of just the rows it needs. The other caveat, is that if the keyword parameter is empty, it should ignore it. Given what's below, is there A) a glaring mistake, or B) a more efficient way to approach this? Here is what I have currently: ALTER PROCEDURE [dbo].[usp_getOppsPaged] @startRowIndex int, @maximumRows int, @city varchar(100) = NULL, @state char(2) = NULL, @zip varchar(10) = NULL, @classification varchar(15) = NULL, @startDateMin date = NULL, @startDateMax date = NULL, @endDateMin date = NULL, @endDateMax date = NULL, @keywords varchar(400) = NULL AS BEGIN SET NOCOUNT ON; ;WITH Results_CTE AS ( SELECT opportunities.*, organizations.*, departments.dept_name, departments.dept_address, departments.dept_building_name, departments.dept_suite_num, departments.dept_city, departments.dept_state, departments.dept_zip, departments.dept_international_address, departments.dept_phone, departments.dept_website, departments.dept_gen_list, ROW_NUMBER() OVER (ORDER BY opp_id) AS RowNum FROM opportunities JOIN departments ON opportunities.dept_id = departments.dept_id JOIN organizations ON departments.org_id=organizations.org_id LEFT JOIN Split(',',@keywords) AS kw ON (title LIKE '%'+kw.s+'%' OR [description] LIKE '%'+kw.s+'%' OR tasks LIKE '%'+kw.s+'%' OR requirements LIKE '%'+kw.s+'%' OR comments LIKE '%'+kw.s+'%') WHERE ( (@city IS NOT NULL AND (city LIKE '%'+@city+'%' OR dept_city LIKE '%'+@city+'%' OR org_city LIKE '%'+@city+'%')) OR (@state IS NOT NULL AND ([state] = @state OR dept_state = @state OR org_state = @state)) OR (@zip IS NOT NULL AND (zip = @zip OR dept_zip = @zip OR org_zip = @zip)) OR (@classification IS NOT NULL AND (classification LIKE '%'+@classification+'%')) OR ((@startDateMin IS NOT NULL AND @startDateMax IS NOT NULL) AND ([start_date] BETWEEN @startDateMin AND @startDateMax)) OR ((@endDateMin IS NOT NULL AND @endDateMax IS NOT NULL) AND ([end_date] BETWEEN @endDateMin AND @endDateMax)) OR ( (@city IS NULL AND @state IS NULL AND @zip IS NULL AND @classification IS NULL AND @startDateMin IS NULL AND @startDateMax IS NULL AND @endDateMin IS NULL AND @endDateMin IS NULL) ) ) ) SELECT * FROM Results_CTE WHERE RowNum >= @startRowIndex AND RowNum < @startRowIndex + @maximumRows; END

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  • Which languages and techniques can I use to improve my coding practices?

    - by Danjah
    I've been offered the opportunity upskill through study, while at work which is great. My background I am mostly self-taught, but have worked with many excellent people over the years - both self-taught and fully educated, and on many decent projects. I have mild experience in Actionscript, I'm getting better every day with my Javascript, and my CSS is angled at best practice, but needs a bit of modernising. I'm a traditional interface developer, I'm not stupid and I like a challenge. My goal I need to start seeing ways of applying better logic, optimising code, refactoring, different styles of development (agile, others?), and.. well I need to try and start thinking like.. a more solid programmer. Its hard to describe, I have good solutions and I'm efficient - but I KNOW that there's a bunch I am missing. I am already employed with a solid career, but I feel the need to fill gaps. My question/s Are there a set of guiding principles you can recommend I focus on to improve the points above? Are there particular programming languages which I might focus on to get a broader overview? Do you think I should avoid particular styles of development, or even languages, while solidifying what might end up being part 'the basics' but hopefully 'advanced programming'? -- Sorry if this appears off topic or something but I figure you're probably some of the best people to ask.

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  • Oracle - UPSERT with update not executed for unmodified values

    - by Buthrakaur
    I'm using following update or insert Oracle statement at the moment: BEGIN UPDATE DSMS SET SURNAME = :SURNAME, FIRSTNAME = :FIRSTNAME, VALID = :VALID WHERE DSM = :DSM; IF (SQL%ROWCOUNT = 0) THEN INSERT INTO DSMS (DSM, SURNAME, FIRSTNAME, VALID) VALUES (:DSM, :SURNAME, :FIRSTNAME, :VALID); END IF; END; This runs fine except that the update statement performs dummy update if the data is same as the parameter values provided. I would not mind the dummy update in normal situation, but there's a replication/synchronization system build over this table using triggers on tables to capture updated records and executing this statement frequently for many records simply means that I'd cause huge traffic in triggers and the sync system. Is there any simple method how to reformulate this code that the update statement wouldn't update record if not necessary without using following IF-EXISTS check code which I find not sleek enough and maybe also not most efficient for this task? DECLARE CNT NUMBER; BEGIN SELECT COUNT(1) INTO CNT FROM DSMS WHERE DSM = :DSM; IF SQL%FOUND THEN UPDATE DSMS SET SURNAME = :SURNAME, FIRSTNAME = :FIRSTNAME, VALID = :VALID WHERE DSM = :DSM AND (SURNAME != :SURNAME OR FIRSTNAME != :FIRSTNAME OR VALID != :VALID); ELSE INSERT INTO DSMS (DSM, SURNAME, FIRSTNAME, VALID) VALUES (:DSM, :SURNAME, :FIRSTNAME, :VALID); END IF; END;

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  • how to synchronize database table and directory with php

    - by twmulloy
    hello, I have a directory with files and a database table with what should be the same files. I would like to be able to synchronize the database table with the directory. What would be the most efficient way to do this? or would I realistically only be able to do this in a brute manner? Here's my approach: 1. retrieve all of the files in the directory as array 2. retrieve all of the filenames in the database table as array 3. loop through the file values in the directory array and use in_array() on the database table array to verify the filename is in that array, and if not then start building an array to insert the missing filenames. run db query to add each missing file row to database table 4. loop through directory array and use in_array() on the directory array and anything not found in the directory array will just be deleted from the table. Is there a better way to go about this? or something better for this in php than in_array()?

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  • Determining polygon intersection and containment

    - by Victor Liu
    I have a set of simple (no holes, no self-intersections) polygons, and I need to check that they don't intersect each other (one can be entirely contained in another; that is okay). I can check this by simply checking the per-vertex inside-ness of one polygon versus other polygons. I also need to determine the containment tree, which is the set of relationships that say which polygon contains any given polygon. Since no polygon can intersect any other, then any contained polygon has a unique container; the "next-bigger" one. In other words, if A contains B contains C, then A is the parent of B, and B is the parent of C, and we don't consider A the parent of C. The question: How do I efficiently determine the containment relationships and check the non-intersection criterion? I ask this as one question because maybe a combined algorithm is more efficient than solving each problem separately. The algorithm should take as input a list of polygons, given by a list of their vertices. It should produce a boolean B indicating if none of the polygons intersect any other polygon, and also if B = true, a list of pairs (P, C) where polygon P is the parent of child C. This is not homework. This is for a hobby project I am working on.

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  • C++ - passing references to boost::shared_ptr

    - by abigagli
    If I have a function that needs to work with a shared_ptr, wouldn't it be more efficient to pass it a reference to it (so to avoid copying the shared_ptr object)? What are the possible bad side effects? I envision two possible cases: 1) inside the function a copy is made of the argument, like in ClassA::take_copy_of_sp(boost::shared_ptr<foo> &sp) { ... m_sp_member=sp; //This will copy the object, incrementing refcount ... } 2) inside the function the argument is only used, like in Class::only_work_with_sp(boost::shared_ptr<foo> &sp) //Again, no copy here { ... sp->do_something(); ... } I can't see in both cases a good reason to pass the boost::shared_ptr by value instead of by reference. Passing by value would only "temporarily" increment the reference count due to the copying, and then decrement it when exiting the function scope. Am I overlooking something? Andrea. EDIT: Just to clarify, after reading several answers : I perfectly agree on the premature-optimization concerns, and I alwasy try to first-profile-then-work-on-the-hotspots. My question was more from a purely technical code-point-of-view, if you know what I mean.

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  • Two radically different queries against 4 mil records execute in the same time - one uses brute force.

    - by IanC
    I'm using SQL Server 2008. I have a table with over 3 million records, which is related to another table with a million records. I have spent a few days experimenting with different ways of querying these tables. I have it down to two radically different queries, both of which take 6s to execute on my laptop. The first query uses a brute force method of evaluating possibly likely matches, and removes incorrect matches via aggregate summation calculations. The second gets all possibly likely matches, then removes incorrect matches via an EXCEPT query that uses two dedicated indexes to find the low and high mismatches. Logically, one would expect the brute force to be slow and the indexes one to be fast. Not so. And I have experimented heavily with indexes until I got the best speed. Further, the brute force query doesn't require as many indexes, which means that technically it would yield better overall system performance. Below are the two execution plans. If you can't see them, please let me know and I'll re-post then in landscape orientation / mail them to you. Brute-force query: Index-based exception query: My question is, based on the execution plans, which one look more efficient? I realize that thing may change as my data grows.

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  • Need Help finding an appropriate task asignment algoritm for a collage project involving coordinatin

    - by Trif Mircea
    Hello. I am a long time lurker here and have found over time many answers regarding jquery and web development topics so I decided to ask a question of my own. This time I have to create a c++ project for collage which should help manage the workflow of a company providing all kinds of services through in the field teams. The ideas I have so far are: client-server application; the server is a dispatcher where all the orders from clients get and the clients are mobile devices (PDAs) each team in the field having one a order from a client is a task. Each task is made up of a series of subtasks. You have a database with estimations on how long a task should take to complete you also know what tasks or subtasks each team on the field can perform based on what kind of specialists made up the team (not going to complicate the problem by adding needed materials, it is considered that if a member of a team can perform a subtask he has the stuff needed) Now knowing these factors, what would a good task assignment algorithm be? The criteria is: how many tasks can a team do, how many tasks they have in the queue, it could also be location, how far away are they from the place but I don't think I can implement that.. It needs to be efficient and also to adapt quickly is the human dispatcher manually assigns a task. Any help or leads would be really appreciated. Also I'm not 100% sure in the idea so if you have another way you would go about creating such an application please share, even if it just a quick outline. I have to write a theoretical part too so even if the ideas are far more complex that what i outlined that would be ok ; I'd write those and implement what I can.

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  • Create new or update existing entity at one go with JPA

    - by Alex R
    A have a JPA entity that has timestamp field and is distinguished by a complex identifier field. What I need is to update timestamp in an entity that has already been stored, otherwise create and store new entity with the current timestamp. As it turns out the task is not as simple as it seems from the first sight. The problem is that in concurrent environment I get nasty "Unique index or primary key violation" exception. Here's my code: // Load existing entity, if any. Entity e = entityManager.find(Entity.class, id); if (e == null) { // Could not find entity with the specified id in the database, so create new one. e = entityManager.merge(new Entity(id)); } // Set current time... e.setTimestamp(new Date()); // ...and finally save entity. entityManager.flush(); Please note that in this example entity identifier is not generated on insert, it is known in advance. When two or more of threads run this block of code in parallel, they may simultaneously get null from entityManager.find(Entity.class, id) method call, so they will attempt to save two or more entities at the same time, with the same identifier resulting in error. I think that there are few solutions to the problem. Sure I could synchronize this code block with a global lock to prevent concurrent access to the database, but would it be the most efficient way? Some databases support very handy MERGE statement that updates existing or creates new row if none exists. But I doubt that OpenJPA (JPA implementation of my choice) supports it. Event if JPA does not support SQL MERGE, I can always fall back to plain old JDBC and do whatever I want with the database. But I don't want to leave comfortable API and mess with hairy JDBC+SQL combination. There is a magic trick to fix it using standard JPA API only, but I don't know it yet. Please help.

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  • Is there any benefit to my rather quirky character sizing convention?

    - by Paul Alan Taylor
    I love things that are a power of 2. I celebrated my 32nd birthday knowing it was the last time in 32 years I'd be able to claim that my age was a power of 2. I'm obsessed. It's like being some Z-list Batman villain, except without the colourful adventures and a face full of batarangs. I ensure that all my enum values are powers of 2, if only for future bitwise operations, and I'm reasonably assured that there is some purpose (even if latent) for doing it. Where I'm less sure, is in how I define the lengths of database fields. Again, I can't help it. Everything ends up being a power of 2. CREATE TABLE Person ( PersonID int IDENTITY PRIMARY KEY ,Firstname varchar(64) ,Surname varchar(128) ) Can any SQL super-boffins who know about the internals of how stuff is stored and retrieved tell me whether there is any benefit to my inexplicable obsession? Is it more efficient to size character fields this way? Can anyone pop in with an "actually, what you're doing works because ....."? I suspect I'm just getting crazier in my older age, but it'd be nice to know that there is some method to my madness.

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  • Titanium TableViewRow classname with custom rows

    - by pancake
    I would like to know in what way the 'className' property of a Ti.UI.TableViewRow helps when creating custom rows. For example, I populate a tableview with custom rows in the following way: function populateTableView(tableView, data) { var rows = []; var row; var title, image; var i; for (i = 0; i < data.length; i++) { title = Ti.UI.createLabel({ text : data[i].title, width : 100, height: 30, top: 5, left: 25 }); image = Ti.UI.createImage({ image : 'some_image.png', width: 30, height: 30, top: 5, left: 5 }); /* and, like, 5+ more views or whatever */ row = Ti.UI.createTableViewRow(); row.add(titleLabel); row.add(image); rows.push(row); } tableView.setData(rows); } Of course, this example of a "custom" row is easily created using the standard title and image properties of the TableViewRow, but that isn't the point. How is the allocation of new labels, image views and other child views of a table view prevented in favour of their reuse? I know in iOS this is achieved by using the method -[UITableView dequeueReusableCellWithIdentifier:] to fetch a row object from a 'reservoir' (so 'className' is 'identifier' here) that isn't currently being used for displaying data, but already has the needed child views laid out correctly in it, thus only requiring to update the data contained within (text, image data, etc). As this system is so unbelievably simple, I have a lot of trouble believing the method employed by the Titanium API does not support this. After reading through the API and searching the web, I do however suspect this is the case. The 'className' property is recommended as an easy way to make table views more efficient in Titanium, but its relation to custom table view rows is not explained in any way. If anyone could clarify this matter for me, I would be very grateful.

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  • Bulletin board - Database optimisation

    - by andrew
    This question is a follow on from this Question The project and problem The project I am currently working on is a bulletin board for a large non-profit organisation. The bulletin board will be used to allow inter-office communication within the organisation. I am building the application and have been having trouble extracting the results that I need from my database because I don't think it is properly normalized and because of limitations in my knowledge of relational database theory and mysql. I would appreciate input into the design of the board in general and in particular, ways that the database structure can be improved to facilitate efficient queries and help me develop this application and future application faster Business Logic The bulletin board will be used in the following way Posting bulletins and responses to bulletins Employees or 'users' in offices around the country will be able to post messages to the bulletin board.Bulletins must be posted to a location and categorised- i'll call these "bulletins". Users will be able to post any number of replies to any one bulletin and users will be able to reply to their own bulletin - i'll call these 'replies'. Rating bulletins and replies Users will be able to either 'like' or 'dislike' a bulletin or a reply and the total number of likes or dislikes will be shown for each bulletin or reply. Viewing the bulletin board and responses Bulletins can be displayed chronologically. Users can sort bulletins chronologically or chronologically by the latest reply to that bulletin(let me know if you need more explanation) When a particular bulletin is selected, replies to that bulletin will be displayed chronologically @PerformanceDBA - edited 10:34 est 28/12/10I have begun implementing the data model. I assume that the 6th data model is the physical model because it contains the associative tables. I am going to post any questions that I have below. I will put up a database dump once I am done. I will then put up a list of all the queries that I need to run on the database and begin writing them. I hope you had a good Christmas. I'm in Canada and there's snow! Implementation of Physical model

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  • help me reason about F# threads

    - by Kevin Cantu
    In goofing around with some F# (via MonoDevelop), I have written a routine which lists files in a directory with one thread: let rec loop (path:string) = Array.append ( path |> Directory.GetFiles ) ( path |> Directory.GetDirectories |> Array.map loop |> Array.concat ) And then an asynchronous version of it: let rec loopPar (path:string) = Array.append ( path |> Directory.GetFiles ) ( let paths = path |> Directory.GetDirectories if paths <> [||] then [| for p in paths -> async { return (loopPar p) } |] |> Async.Parallel |> Async.RunSynchronously |> Array.concat else [||] ) On small directories, the asynchronous version works fine. On bigger directories (e.g. many thousands of directories and files), the asynchronous version seems to hang. What am I missing? I know that creating thousands of threads is never going to be the most efficient solution -- I only have 8 CPUs -- but I am baffled that for larger directories the asynchronous function just doesn't respond (even after a half hour). It doesn't visibly fail, though, which baffles me. Is there a thread pool which is exhausted? How do these threads actually work?

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  • design an extendable database model

    - by wishi_
    Hi! Currently I'm doing a project whose specifications are unclear - well who doesn't. I wonder what's the best development strategy to design a DB, that's going to be extended sooner or later with additional tables and relations. I want to include "changeability". My main concern is that I want to apply design patterns (it's a university project) and I want to separate the constant factors from those, that change by choosing appropriate design patterns - in my case MVC and a set of sub-patterns at model level. When it comes to the DB however, I may have to resdesign my model in my MVC approach, because my domain model at a later stage my require a different set of classes representing the DB tables. I use Hibernate as an abstraction layer between DB and application. Would you start with a very minimal DB, just a few tables and relations? And what if I want an efficient DB, too? I wonder what strategies are applied in the real world. Stakeholder analysis for example isn't a sufficient planing solution when it comes to changing requirements. I think - at a DB level - my design pattern ends. So there's breach whose impact I'd like to minimize with a smart strategy.

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  • C#. How to pass message from unsafe callback to managed code?

    - by maxima120
    Is there a simple example of how to pass messages from unsafe callback to managed code? I have a proprietary dll which receives some messages packed in structs and all is coming to a callback function. The example of usage is as follows but it calls unsafe code too. I want to pass the messages into my application which is all managed code. *P.S. I have no experience in interop or unsafe code. I used to develop in C++ 8 yrs ago but remember very little from that nightmarish times :) P.P.S. The application is loaded as hell, the original devs claim it processes 2mil messages per sec.. I need a most efficient solution.* static unsafe int OnCoreCallback(IntPtr pSys, IntPtr pMsg) { // Alias structure pointers to the pointers passed in. CoreSystem* pCoreSys = (CoreSystem*)pSys; CoreMessage* pCoreMsg = (CoreMessage*)pMsg; // message handler function. if (pCoreMsg->MessageType == Core.MSG_STATUS) OnCoreStatus(pCoreSys, pCoreMsg); // Continue running return (int)Core.CALLBACKRETURN_CONTINUE; } Thank you.

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  • Fast serarch of 2 dimensional array

    - by Tim
    I need a method of quickly searching a large 2 dimensional array. I extract the array from Excel, so 1 dimension represents the rows and the second the columns. I wish to obtain a list of the rows where the columns match certain criteria. I need to know the row number (or index of the array). For example, if I extract a range from excel. I may need to find all rows where column A =”dog” and column B = 7 and column J “a”. I only know which columns and which value to find at run time, so I can’t hard code the column index. I could use a simple loop, but is this efficient ? I need to run it several thousand times, searching for different criteria each time. For r As Integer = 0 To UBound(myArray, 0) - 1 match = True For c = 0 To UBound(myArray, 1) - 1 If not doesValueMeetCriteria(myarray(r,c) then match = False Exit For End If Next If match Then addRowToMatchedRows(r) Next The doesValueMeetCriteria function is a simple function that checks the value of the array element against the query requirement. e.g. Column A = dog etc. Is it more effiecent to create a datatable from the array and use the .select method ? Can I use Linq in some way ? Perhaps some form of dictionary or hashtable ? Or is the simple loop the most effiecent ? Your suggestions are most welcome.

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  • N-gram split function for string similarity comparison

    - by Michael
    As part of excersise to better understand F# which I am currently learning , I wrote function to split given string into n-grams. 1) I would like to receive feedback about my function : can this be written simpler or in more efficient way? 2) My overall goal is to write function that returns string similarity (on 0.0 .. 1.0 scale) based on n-gram similarity; Does this approach works well for short strings comparisons , or can this method reliably be used to compare large strings (like articles for example). 3) I am aware of the fact that n-gram comparisons ignore context of two strings. What method would you suggest to accomplish my goal? //s:string - target string to split into n-grams //n:int - n-gram size to split string into let ngram_split (s:string, n:int) = let ngram_count = s.Length - (s.Length % n) let ngram_list = List.init ngram_count (fun i -> if( i + n >= s.Length ) then s.Substring(i,s.Length - i) + String.init ((i + n) - s.Length) (fun i -> "#") else s.Substring(i,n) ) let ngram_array_unique = ngram_list |> Seq.ofList |> Seq.distinct |> Array.ofSeq //produce tuples of ngrams (ngram string,how much occurrences in original string) Seq.init ngram_array_unique.Length (fun i -> (ngram_array_unique.[i], ngram_list |> List.filter(fun item -> item = ngram_array_unique.[i]) |> List.length) )

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  • Refactoring - Speed increase

    - by Michael G
    How can I make this function more efficient. It's currently running at 6 - 45 seconds. I've ran dotTrace profiler on this specific method, and it's total time is anywhere between 6,000ms to 45,000ms. The majority of the time is spent on the "MoveNext" and "GetEnumerator" calls. and example of the times are 71.55% CreateTableFromReportDataColumns - 18, 533* ms - 190 calls -- 55.71% MoveNext - 14,422ms - 10,775 calls What can I do to speed this method up? it gets called a lot, and the seconds add up: private static DataTable CreateTableFromReportDataColumns(Report report) { DataTable table = new DataTable(); HashSet<String> colsToAdd = new HashSet<String> { "DataStream" }; foreach (ReportData reportData in report.ReportDatas) { IEnumerable<string> cols = reportData.ReportDataColumns.Where(c => !String.IsNullOrEmpty(c.Name)).Select(x => x.Name).Distinct(); foreach (var s in cols) { if (!String.IsNullOrEmpty(s)) colsToAdd.Add(s); } } foreach (string col in colsToAdd) { table.Columns.Add(col); } return table; }

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  • IPad SQLite Push and Pull Data from external MS SQL Server DB

    - by MattyD
    This carries on from my previous post (http://stackoverflow.com/questions/4182664/ipad-app-pull-and-push-relational-data). My plan is that when the ipad application starts I am going to pull data (config data i.e. Departments, Types etc etc relational data that is used across the system) from a webhosted MS SQL Server DB via a webservice and populate it into an SQL Lite DB on the IPad. Then when I load a listing I will pull the data over the line again via a webservice and populate it into the SQL Lite db on the ipad (than just run select commands to populate the listing). My questions are: 1. What is the most efficient way to transfer data across the line via the web? Everyone seems to do it a different way. My idea is that I will have a webService for each type of data pull (e.g. RetrieveContactListing) that will query the db and than convert that data into "something" to send across the line. My question really is what is the "something" that it should be converting into? 2. Everyone talks about odata services. Is this suited for applications where complex read and writes are needed? Ive created a simple iphone app before that talked to an sql server db (i just sent my own structured xml across the line) but now with this app the data calls are going to be a lot larger so efficiency is key.

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  • Deserialize xml which uses attribute name/value pairs

    - by Bodyloss
    My application receives a constant stream of xml files which are more or less a direct copy of the database record <record type="update"> <field name="id">987654321</field> <field name="user_id">4321</field> <field name="updated">2011-11-24 13:43:23</field> </record> And I need to deserialize this into a class which provides nullable property's for all columns class Record { public long? Id { get; set; } public long? UserId { get; set; } public DateTime? Updated { get; set; } } I just cant seem to work out a method of doing this without having to parse the xml file manually and switch on the field's name attribute to store the values. Is their a way this can be achieved quickly using an XmlSerializer? And if not is their a more efficient way of parsing it manually? Regards and thanks My main problem is that the attribute name needs to have its value set to a property name and its value as the contents of a <field>..</field> element

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  • Invoking a method overloaded where all arguments implement the same interface

    - by double07
    Hello, My starting point is the following: - I have a method, transform, which I overloaded to behave differently depending on the type of arguments that are passed in (see transform(A a1, A a2) and transform(A a1, B b) in my example below) - All these arguments implement the same interface, X I would like to apply that transform method on various objects all implementing the X interface. What I came up with was to implement transform(X x1, X x2), which checks for the instance of each object before applying the relevant variant of my transform. Though it works, the code seems ugly and I am also concerned of the performance overhead for evaluating these various instanceof and casting. Is that transform the best I can do in Java or is there a more elegant and/or efficient way of achieving the same behavior? Below is a trivial, working example printing out BA. I am looking for examples on how to improve that code. In my real code, I have naturally more implementations of 'transform' and none are trivial like below. public class A implements X { } public class B implements X { } interface X { } public A transform(A a1, A a2) { System.out.print("A"); return a2; } public A transform(A a1, B b) { System.out.print("B"); return a1; } // Isn't there something better than the code below??? public X transform(X x1, X x2) { if ((x1 instanceof A) && (x2 instanceof A)) { return transform((A) x1, (A) x2); } else if ((x1 instanceof A) && (x2 instanceof B)) { return transform((A) x1, (B) x2); } else { throw new RuntimeException("Transform not implemented for " + x1.getClass() + "," + x2.getClass()); } } @Test public void trivial() { X x1 = new A(); X x2 = new B(); X result = transform(x1, x2); transform(x1, result); }

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