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  • How to use locks/synchronization here

    - by MasterGberry
    I have this code block here and i need to make sure the rankedPlayersWaitingForMatch is synchronized between threads properly. I was going to use synchronize but that i don't think will work here because of the variable being used in the if statement. I read online about final Lock lock = new ReentrantLock(); but I am a bit confused on how to use it in this case properly with the try/finally block. Can I get a quick example? Thanks // start synchronization if (rankedPlayersWaitingForMatch.get(rankedType).size() >= 2) { Player player1 = rankedPlayersWaitingForMatch.get(rankedType).remove(); Player player2 = rankedPlayersWaitingForMatch.get(rankedType).remove(); // end synchronization // ... I don't want this all to be synchronized, just after the first 2 remove() } else { // end synchronization // ... }

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  • SQL Server deadlock issue

    - by George2
    Hello everyone, I am using SQL Server 2008 Enterprise. I am wondering whether dead lock issue is only caused by cross dependencies (e.g. task A has lock on L1 but waits on lock on L2, and at the same time, task B has lock on L2 but waits on lock on L1)? Are there any other reasons and scenarios which will cause deadlock? Are there any other way which will causes dead lock -- e.g. timeout (a S/I/D/U statement do not return for a very long time, and deadlock error will be returned) or can not acquire lock for a long time but not caused by cross-dependencies (e.g. task C needs to get lock on table T, but another task D acquire the lock on table T without releasing the lock, which causes task C not be able to get lock on table T for a long time)? thanks in advance, George

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  • Combining 2 Linq queries into 1

    - by Mike Fielden
    Given the following information, how can I combine these 2 linq queries into 1. Having a bit of trouble with the join statement. 'projectDetails' is just a list of ProjectDetails ProjectDetails (1 to many) PCardAuthorizations ProjectDetails (1 to many) ExpenditureDetails Notice I am grouping by the same information and selecting the same type of information var pCardAccount = from c in PCardAuthorizations where projectDetails.Contains(c.ProjectDetail) && c.RequestStatusId == 2 group c by new { c.ProjectDetail, c.ProgramFund } into g select new { Key = g.Key, Sum = g.Sum(x => x.Amount) }; var expenditures = from d in ExpenditureDetails where projectDetails.Contains(d.ProjectDetails) && d.Expenditures.ExpenditureTypeEnum == 0 group d by new { d.ProjectDetails, d.ProgramFunds } into g select new { Key = g.Key, Sum = g.Sum(y => y.ExpenditureAmounts.FirstOrDefault(a => a.IsCurrent && !a.RequiresAudit).CommittedMonthlyRecords.ProjectedEac) };

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  • what type of errors can we handle using system define unnamed exception in sqlplus?

    - by Aspirant
    I have been trying to access the below code DECLARE N_DEPTNO DEPT.DEPTNO %TYPE :=&DEPT_NUM; V_DNAME DEPT.DNAME %TYPE; NOT_ENOUGH_VALUES EXCEPTION; PRAGMA EXCEPTION_INIT(NOT_ENOUGH_VALUES,-06502); BEGIN SELECT DNAME,LOC INTO DNAME FROM DEPT WHERE DEPTNO = N_DEPTNO; DBMS_OUTPUT.PUT_LINE('Successfully Fetched !!'); EXCEPTION WHEN NOT_ENOUGH_VALUES THEN DBMS_OUTPUT.PUT_LINE('No Enough Values ... '); END; It is still showing error message after specified it in EXCEPTION block. Can i handle these type of errors using PRAGMA EXCEPTION_INIT i.e not providing enough values in the select statement... If not what type of errors can be handled in System Defined Unnamed Exception using PRAGMA EXCEPTION_INIT.

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  • for loop will not loop

    - by Bjørn Jostein Aurheim
    I have a for loop that I will use to compute time intervals to add to an ArrayList. The problem is that I can not prove that the for loop is being executed. Nothing is printed when using the system.out.println() statement, and nothing is added to the array from inside the loop ... any sugestions? // lager tidspunkter og legger disse inn i en Array kalt tider tid.setTimer(16); tid.setMinutter(0); tid.setSekunder(0); tider.add(tid.asString());// String "16:00" is added as it should System.out.println("tiden er: "+tid.asString());// gives 16:00 printed for(int i=0;i>12;i++){ System.out.println("er i løkken");// gives nothing printed tid.increaseMinutter(30); System.out.println(tid.asString());// gives nothing printed tider.add(tid.asString()); }

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  • Algorithm design: can you provide a solution to the multiple knapsack problem?

    - by MalcomTucker
    I am looking for a pseudo-code solution to what is effectively the Multiple Knapsack Problem (optimisation statement is halfway down the page). I think this problem is NP Complete so the solution doesn't need to be optimal, rather if it is fairly efficient and easily implemented that would be good. The problem is this: I have many work items, with each taking a different (but fixed and known) amount of time to complete. I need to divide these work items into groups so as to have the smallest number of groups (ideally), with each group of work items taking no longer than a given total threshold - say 1 hour. I am flexible about the threshold - it doesnt need to be rigidly applied, though should be close. My idea was to allocate work items into bins where each bin represents 90% of the threshold, 80%, 70% and so on. I could then match items that take 90% to those that take 10%, and so on. Any better ideas?

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  • Check value at insert

    - by ThreeFingerMark
    Hello, i have this three tables. Table: Item Columns: ItemID, Title, Content, NoChange (Date) Table: Tag Columns: TagID, Title Table: ItemTag Columns: ItemID, TagID In the Item Table is a Field with NoChange, if this field = true no Tag is allowed to insert a ItemTag value with this ItemID. How can i check this in the insert? For Updates i have this Statement: UPDATE ItemTag SET TagID = ? where ItemID = ? AND TagID = ? AND exists ( select ItemID from Item where ItemID = ? AND NoChange is null)"); Thank you.

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  • Basic Client-Server Design for persistent connections?

    - by cam
    Here's as far as I understand it: Client & Server make connection Client sends server data Server interprets data, sends client data So on, and so forth, until client sends disconnect signal. I'm just wondering about implementation. Step 2 and 3 are confusing to me, maybe I'm over-complicating it. Is there anymore to interpreting the data than a giant switch statement? Any good books on client/server design? Specifically talking about multithreaded servers, scalability, and message design (byte 1 = header info, byte 2 = blah blah, etc)? Specifically geared towards C++.

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  • How can two threads access a common array of buffers with minimal blocking ? (c#)

    - by Jelly Amma
    Hello, I'm working on an image processing application where I have two threads on top of my main thread: 1 - CameraThread that captures images from the webcam and writes them into a buffer 2 - ImageProcessingThread that takes the latest image from that buffer for filtering. The reason why this is multithreaded is because speed is critical and I need to have CameraThread to keep grabbing pictures and making the latest capture ready to pick up by ImageProcessingThread while it's still processing the previous image. My problem is about finding a fast and thread-safe way to access that common buffer and I've figured that, ideally, it should be a triple buffer (image[3]) so that if ImageProcessingThread is slow, then CameraThread can keep on writing on the two other images and vice versa. What sort of locking mechanism would be the most appropriate for this to be thread-safe ? I looked at the lock statement but it seems like it would make a thread block-waiting for another one to be finished and that would be against the point of triple buffering. Thanks in advance for any idea or advice. J.

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  • problem in counting two fields in one query

    - by Mac Taylor
    hey guys i need to count new private messages and old one from a table so first thing come to mind is using mysql_num_rows and easy thing to do // check new pms $user_id = $userinfo['user_id']; $sql = "SELECT author_id FROM bb3privmsgs_to WHERE user_id='$user_id' AND (pm_new='1' OR pm_unread='1')"; $result = $db->sql_query($sql) ; $new_pms = $db->sql_numrows($result); $db->sql_freeresult($result); // check old pms $sql = "SELECT author_id FROM bb3privmsgs_to WHERE user_id='$user_id' AND (pm_new='0' OR pm_unread='0')"; $result = $db->sql_query($sql) ; $old_pms = $db->sql_numrows($result); $db->sql_freeresult($result); but how can i count these two fields just in one statement and shorter lines ?~

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  • What should be proper location for sqlit3 database file?

    - by Elliot Chen
    Hi, Everyone: I'm using a sqlite3 database to store app's data. Instead of building a database within program, I introduced an existing db file: 'abc.sqlite' into my project and put it under my 'Resources' folder. So, I think this db file should be inside of 'bundle', so at my init function, I used following statement to read it out: NSString *path = [[NSBundle mainBundle] pathForResource:@"abc" ofType:"sqlite"]; if(sqlite3_open([path UTF8String], &database) != SQLITE_OK) ... It's ok that this db can be opened and data can be retrieved from it. BUT, someone told me that it's better to copy this db file into user folder: such as 'Document'. So, my question is: is it ok to use this db from main bundle directly or copy it to user folder then use that copy. Which is better? Thank you very much!

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  • Run Sql*Plus commands on Application Express

    - by pesantos
    Hi, I am new to PL/SQL, I'm trying to execute the commands that I learned at the course. VARIABLE area NUMBER DECLARE radius NUMBER(2) := &s_radius; pi CONSTANT NUMBER := 3.14; BEGIN :area := pi * radius * radius; END; I understand that I can run this using SqlPlus, but I remember my teacher was running this from the web browser using Application Express. I try to run the same commands there, at HOME SQLSQL Commands, but I keep getting the error "ORA-00900: invalid SQL statement" . Can you help me run it in Application Express or point me to a way where I can use an editor to run these course exercises? Thanks!

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  • Sample/Example needed for a table/field setup

    - by acctman
    Can someone explain the statement below to me with a working sample/example. thanks in advance. You can not create duplicate fields, but simply add a single extra field, "coupleId", which would have a unique id for each couple; and two rows (one for each person) per couple; then JOIN the table against itself with a constraint like a.coupleId = b.coupleId AND a.id < b.id so that you can condense the data into a single result row for a given couple.

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  • Python and sqlite3 - importing and exporting databases

    - by JPC
    I'm trying to write a script to import a database file. I wrote the script to export the file like so: import sqlite3 con = sqlite3.connect('../sqlite.db') with open('../dump.sql', 'w') as f: for line in con.iterdump(): f.write('%s\n' % line) Now I want to be able to import that database. I tried: import sqlite3 con = sqlite3.connect('../sqlite.db') f = open('../dump.sql','r') str = f.read() con.execute(str) but I'm not allowed to execute more than one statement. Is there a way to get it to run a .sql script directly?

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  • Question About Abstract Classes?

    - by IbrarMumtaz
    URL: Link (1) According to this wesbite .. you cannot implement Abstract classes but derive from them. This makes sense and I have read this many times. Like an interface, you cannot implement an instance of an abstract class, however you can implement methods, fields, and properties in the abstract class that can be used by the child class. But on MSDN URL: TextWriter CLass on MSDN TextWriter is an abstract class but it has two constructors defined ... and according to the MS 70-536 book, the following statement is valid: TextWriter tw = new File.CreateText("myFile.Txt") The static file class and it's CreateText method is fine by me as I have studied it on MSDN but can somebody explain this little contradiction I have found? Surely I am not the first? Why is instantaion of base abstract classes possible????

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  • c# reading integer fields from database

    - by arnoldino
    what is wrong with this code? try { if (cmd == null) getConnection(); cmd.CommandText = "Select id from HMonthInventary where machine_id=37"; SQLiteDataReader reader = cmd.ExecuteReader(); if (reader.HasRows==true) { reader.Read(); string s = reader[0].ToString(); // return first element reader.Close(); return s; } reader.Close(); return null; } catch (Exception e) { MessageBox.Show("Caught exception: " + e.Message+"|"+cmd.CommandText); return null; } I checked the sql statement, it turns the right value. why can't I read it? the returnvalue is "".

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  • Treat a void function as a value

    - by Brendan Long
    I'm writing some terrible, terrible code, and I need a way to put a free() in the middle of a statement. The actual code is: int main(){ return printf("%s", isPalindrome(fgets(malloc(1000), 1000, stdin))?"Yes!\n":"No!\n") >= 0; // leak 1000 bytes of memory } I was using alloca(), but I can't be sure that will actually work on my target computer. My problem is that free returns void, so my code has this error message: error: void value not ignored as it ought to be The obvious idea I had was: int myfree(char *p){ free(p); return 0; } Which is nice in that it makes the code even more unreadable, but I'd prefer not to add another function. I also briefly tried treating free() as a function pointer, but I don't know if that would work, and I don't know enough about C to do it properly. Note: I know this is a terrible idea. Don't try this at home kids.

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  • C# property in a form class only accessable after formload event

    - by Spooky2010
    using vs2008, c# Howdy, Im instantiating and calling Form B from Form A. FormB has some custom properties, to allow me to pass it things like sqlAdaptors and dataset instances. When i instantiate and show Form B from Form A as a dialog form with a Using statement, it all works fine, but i find the properties i pass are not available in Form B until after the form_load event has fired. I was under the impression the properties when passed to a instantiated class should be available from a constructor, but this is not the case. If it try to access the properties before the form load event i get a null reference exception. Is this correct behavior ? It is very annoying. thanks for any help

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  • Is this __import__ functionality correct?

    - by Jason Baker
    I have a package named jiva_tasks, which I'm trying to import via celery (using the CELERY_IMPORTS attribute of celeryconfig. The import statement that celery is using is this: __import__(module, [], [], ['']) Oddly enough, when this syntax is used, the module gets imported twice, once as jiva_tasks and another time as jiva_tasks. (with a period at the end). Now, chances are good that celery should be passing in globals rather than an empty list, but this seems broken to me. It seems odd that even if given the wrong arguments, __import__ would import something that isn't a valid python module name. I know that the way to fix this is to pass in globals, but I want to understand why I'm getting this result. Is this a bug, or is there something I don't understand about how __import__ is working? Update: It also seems to be working fine if I use importlib.

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  • Catching "NullPointerExceptions" in JavaScript

    - by Lenni
    I'm writing quite a bit of code in Prototype.js which returns null if a DOM-id wasn't found. $("someId").show(); If someId doesn't exist, a method will be called on null, which halts the entire program, in effect disabling all JS effects after the error. I could just check for null before executing such a statement, but this is getting tiring. I would like to catch an exception but I'm not sure which one its is. MDC lists the following ECMA Script error types: * Error * EvalError * RangeError * ReferenceError * SyntaxError * TypeError * URIError * DOMException * EventException * RangeException Also, do browsers have a unified way of dealing with a method call on null?

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  • Convert Enum to String

    - by Eric Weilnau
    Which is the preferred way to convert an Enum to a String in .NET 3.5? Enum.GetName Enum.Format toString Why should I prefer one of these over the others? Does one perform better? Justification for Accepted Answer Based on the forum post in panesofglass answer, it appears that Microsoft indirectly endorses the following method of converting an enum value to a string. Do not convert an enum value to a string using built-in enum methods. ... This will cause problems when Dotfuscating. You should not use enum.ToString(), enum.GetNames(), enum.GetName(), enum.Format() or enum.Parse() to convert an enum to a string. Instead, use a switch statement, and also internationalize the names if necessary.

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  • LINQ2SQL: orderby note.hasChildren(), name ascending

    - by Peter Bridger
    I have a hierarchical data structure which I'm displaying in a webpage as a treeview. I want to data to be ordered to first show nodes ordered alphabetically which have no children, then under these nodes ordered alphabetically which have children. Currently I'm ordering all nodes in one group, which means nodes with children appear next to nodes with no children. I'm using a recursive method to build up the treeview, which has this LINQ code at it's heart: var filteredCategory = from c in category orderby c.Name ascending where c.ParentCategoryId == parentCategoryId && c.Active == true select c; So this is the orderby statement I want to enhance. Shown below is the database table structure: [dbo].[Category]( [CategoryId] [int] IDENTITY(1,1) NOT NULL, [Name] [varchar](100) NOT NULL, [Level] [tinyint] NOT NULL, [ParentCategoryId] [int] NOT NULL, [Selectable] [bit] NOT NULL CONSTRAINT [DF_Category_Selectable] DEFAULT ((1)), [Active] [bit] NOT NULL CONSTRAINT [DF_Category_Active] DEFAULT ((1))

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  • What is the impact/limitation of oracle select with large number of bind variables?

    - by Igal Serban
    We had our oracle server chocking during processing a select statement with close to 3500(!!) bind variables. This select is, obviously, build dynamically by code that we can't change. During the execution of this select the db server went to 100% cpu usage and our system almost halted. We know how to reproduce this problem. So we can prevent this specific condition. But I am wondering if there is a way to protect the db ( by configuration) from this type of problems.

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  • Android NDK R5 and support of C++ exception

    - by plaisthos
    Hi, I am trying to use the NDK 5 full C++ gnustl: sources/cxx-stl/gnu-libstdc++/README states: This implementation fully supports C++ exceptions and RTTI. But all attempts using exceptions fail. An alternative NDK exists on http://www.crystax.net/android/ndk-r4.php. Even the hello-jni example from that site does not work. Compliation works after creating an Application.xml with APP_STL := gnustl_static But it dies the same horrific death as my own experiments. Am I am missing something or is the statement in the README just plain wrong?

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  • Modifying annotation attribute value at runtime in java

    - by Lici
    Hi folks: some methods in our model pojos have been annotated like this: @Column(name="cli_clipping_id", updatable=false, columnDefinition = "varchar(" + ModelUtils.ID_LENGTH + ") COLLATE utf8_bin") columnDefinition attribute is database vendor dependant, so when trying to drop schema in HSQLDB using Hibernate it fails: [ERROR] 16 jun 12:58:42.480 PM main [org.hibernate.tool.hbm2ddl.SchemaExport] Unexpected token: COLLATE in statement [create table cms.edi_editorial_obj (edi_uuid varchar(23) COLLATE ] To fix this, i'm thinking on this solution (but don't want to spend time if it isn't possible) , at runtime, for each method column annotated: Get @Column annotation Create a copy of the column annotation, setting columnDefinition null using javaassist. set column method annotation to the copy column annotation object overriding the old one (i don't know it this is possible) Is it possible to "hack" these methods this way? Any help would be much appreciated ...

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