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  • Using locks inside a loop

    - by Xaqron
    // Member Variable private readonly object _syncLock = new object(); // Now inside a static method foreach (var lazyObject in plugins) { if ((string)lazyObject.Metadata["key"] = "something") { lock (_syncLock) { if (!lazyObject.IsValueCreated) lazyObject.value.DoSomething(); } return lazyObject.value; } } Here I need synchronized access per loop. There are many threads iterating this loop and based on the key they are looking for, a lazy instance is created and returned. lazyObject should not be created more that one time. Although Lazy class is for doing so and despite of the used lock, under high threading I have more than one instance created (I track this with a Interlocked.Increment on a volatile shared int and log it somewhere). The problem is I don't have access to definition of Lazy and MEF defines how the Lazy class create objects. My questions: 1) Why the lock doesn't work ? 2) Should I use an array of locks instead of one lock for performance improvement ?

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  • Do I need to syncronize thread access to an int

    - by Martin Harris
    I've just written a method that is called by multiple threads simultaneously and I need to keep track of when all the threads have completed, the code uses this pattern: private void RunReport() { _reportsRunning++; try { //code to run the report } finally { _reportsRunning--; } } This is the only place within the code that _reportsRunning's value is changed, and the method takes about a second to run. Occasionally when I have more than six or so threads running reports together the final result for _reportsRunning can get down to -1, if I wrap the calls to _runningReports++ and _runningReports-- in a lock then the behaviour appears to be correct and consistant. So, to the question: When I was learning multithreading in C++ I was taught that you didn't need to synchronize calls to increment and decrement operations because they were always one assembly instruction and therefore it was impossible for the thread to be switched out mid-call. Was I taught correctly, and if so how come that doesn't hold true for C#?

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  • how can we achieve second application read that file when first application not modifying it

    - by soField
    i have two application first application is bash second is java which one of them is periodically deleting and recreating a specific file (first) the other one is also periodically reading this file and process it in it's own logic (second) how can we achieve second application read that file when first application not modifying it my aim is to force second app read the file only when content of file fully written inside it how can achieve this goal ?

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  • Multi-threading concept and lock in c#

    - by Neeraj
    I read about lock, though not understood nothing at all. My question is why do we use a un-used object and lock that and how this makes something thread-safe or how this helps in multi-threading ? Isn't there other way to make thread-safe code. public class test { private object Lock { get; set; } ... lock (this.Lock) { ... } ... } Sorry is my question is very stupid, but i don't understand, although i've used it many times.

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  • Thread-Safe lazy instantiating using MEF

    - by Xaqron
    // Member Variable private static readonly object _syncLock = new object(); // Now inside a static method foreach (var lazyObject in plugins) { if ((string)lazyObject.Metadata["key"] = "something") { lock (_syncLock) { // It seems the `IsValueCreated` is not up-to-date if (!lazyObject.IsValueCreated) lazyObject.value.DoSomething(); } return lazyObject.value; } } Here I need synchronized access per loop. There are many threads iterating this loop and based on the key they are looking for, a lazy instance is created and returned. lazyObject should not be created more that one time. Although Lazy class is for doing so and despite of the used lock, under high threading I have more than one instance created (I track this with a Interlocked.Increment on a volatile static int and log it somewhere). The problem is I don't have access to definition of Lazy and MEF defines how the Lazy class create objects. I should notice the CompositionContainer has a thread-safe option in constructor which is already used. My questions: 1) Why the lock doesn't work ? 2) Should I use an array of locks instead of one lock for performance improvement ?

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  • What is better and why to use List as thread safe: BlockingCollection or ReaderWriterLockSlim or lock?

    - by theateist
    I have System.Collections.Generic.List _myList and many threads can read from it or add items to it simultaneously. From what I've read I should using 'BlockingCollection' so this will work. I also read about ReaderWriterLockSlim' and 'lock', but I don't figure out how to use them instead ofBlockingCollection`, so my question is can I do the same with: ReaderWriterLockSlim lock instead of using 'BlockingCollection'. If YES, can you please provide simple example and what pros and cons of using BlockingCollection, ReaderWriterLockSlim, lock?

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  • detection of 'flush tables with read lock' in php

    - by theduke0
    I would like to know from my application if a myisam table can accept writes (i.e. not locked). If an exception is thrown, everything is fine as I can catch this and log the failed statement to a file. However, if a 'flush tables with read lock' command has been issued (possibly for backup), the query I send will pretty much hang out forever. If one table is locked at a time, insert delayed works well. But when this global lock is applied, my query just waits. The query I run is an insert statement. If this statement fails or hangs, user experience is degraded. I need a way to send the query to the server and forget about it (pretty much). Does anyone have any suggestions on how to deal with this? -set a query timeout? -run asyncronous request and allow for the lock to expire while application continues? -fork my php process? Please let me know if I can provide and clarification or details.

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  • Lock innoDB table temporarily

    - by Industrial
    Hi everyone, I make bigger inserts consisting of a couple of thousand rows in my current web app and I would like to make sure that no one can do anything but read the table, until the inserts have been done. What is the best way to do this while keeping the read availability open for normal, non-admin users? Thanks!

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  • Best practice for avoiding locks on a heavily read table?

    - by Luiggi
    Hi, I have a big database (~4GB), with 2 large tables (~3M records) having ~180K SELECTs/hour, ~2k UPDATEs/hour and ~1k INSERTs+DELETEs/hour. What would be the best practice to guarantee no locks for the reading tasks while inserting/updating/deleting? I was thinking about using a NOLOCK hint, but there is so much discussed about this (is good, is bad, it depends) that I'm a bit lost. I must say I've tried this in a dev environment and I didn't find any problems, but I don't want to put it on production until I get some feedback... Thank you! Luiggi

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  • ActiveRecord and transactionsin between `before_save` and `save`

    - by JP
    I have some logic in before_save whereby (only) when some conditions are met I let the new row be created with special_number equal to the maximum special_number in the database + 1. (If the conditions aren't met then I do something different, so I can't use auto-increments) My worry is that two threads acting on this database at once might pick the same special_number if the second is executed while the first is saving. Is there way to lock the database between before_save and finishing the save, but only in some cases? I know all saves are sent in transactions, will this do the job for me? def before_save if things_are_just_right # -- Issue some kind of lock? # -- self.lock? I have no idea # Pick new special_number new_special = self.class.maximum('special_number') + 1 write_attribute('special_number',new_special) else # No need to lock in this case write_attribute('special_number',some_other_number) end end

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  • VB.NET Program Locks Up with Internet Explorer Opened

    - by aaronsj
    I'm using Visual Studio 2008 and developing a VB.NET application. I'm having strange lockup problems with my program, but only when Internet explorer 8 is opened. When I cover my form with another window and then uncover it, I find that it has locked up. My program has no references to IE and the only thing it even has to do with IE is using Process.Start with a web address. My program works fine and exactly as it should, but only when IE is not opened. Does anyone know why a program would lock up only while IE is running? Edit: I've done some digging and I've found the offending thread in my program. I don't know what starts this thread or what it does, but when I kill it, my program no longer freezes. The thread is one of the CreateApplicationContext threads, here is the last few items in the stack trace of that thread. 6 ntkrnlpa.exe+0x897bc 7 ntdll.dll!KiFastSystemCallRet 8 mscorwrks.dll!LogHelp_TerminateOnAssert+0x61 9 mscorwrks.dll!DllUnregisterServerInternal+0x10523 10 mscorwrks.dll!DllUnregisterServerInternal+0x10542 11 mscorwrks.dll!StrongNameErrorInfo+0x34387 12 mscorwrks.dll!StrongNameErrorInfo+0x34815 13 mscorwrks.dll!CreateApplicationContext+0xbc35 14 KERNEL32.dll!GetModuleHandleA+0xdf Process explorer says my program is using no CPU nor throwing any exceptions while it is hung.

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  • What happens if you break out of a Lock() statement?

    - by cyclotis04
    I'm writing a program which listens to an incoming TcpClient and handles data when it arrives. The Listen() method is run on a separate thread within the component, so it needs to be threadsafe. If I break out of a do while loop while I'm within a lock() statement, will the lock be released? If not, how do I accomplish this? Thanks! (Any other advice on the subject of Asynchronous TCP Sockets is welcome as well.) private void Listen() { do { lock (_client) { if (!_client.Connected) break; lock (_stateLock) { if (!_listening) break; if (_client.GetStream().DataAvailable) HandleData(); } } Thread.Sleep(0); } while (true); }

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  • Real World Examples of read-write in concurrent software

    - by Richard Fabian
    I'm looking for real world examples of needing read and write access to the same value in concurrent systems. In my opinion, many semaphores or locks are present because there's no known alternative (to the implementer,) but do you know of any patterns where mutexes seem to be a requirement? In a way I'm asking for candidates for the standard set of HARD problems for concurrent software in the real world.

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  • How can I modify the application file of an application that is currently running (on Linux)?

    - by Hach-Que
    I have an application running called AppFS. This application has an ext2 filesystem just attached to the end of the file (it's positioned so that the application binary exists in a 1MB spacing area, followed by the ext2 data). Now I've got FUSE embedded in the program and I've managed to extract the filesystem out of the application data into a temporary file so that FUSE can mount / use it. The problem I have now is writing the temporary file back into the application file. I get "Text file busy" presumably because the application has locked itself and won't let writes occur. Is there a way I can force the file to become unlocked so I can write data to it? (It's important to note that I'm not changing the application binary area - just rewriting the ext2 component.) It needs to be unlocked without requiring root permissions (unlocked by the same user who started the application).

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  • Copy a value based on criteria Salesforce

    - by Robert
    Hi all, On a Salesforce.com opportunity I have a number of custom fields that are potential options that the end client will eventually select. Option 1 (Desc Field) Option 1 (Value) Option 2 (Desc Field) Option 2 (Value) Option 3 (Desc Field) Option 3 (Value) At a future point the user will ultimately choose one of the options as the preferred option. What I want is then the value for the chosen option to be stored in another field without the user having to enter it again. A “nice to have” would also be that all 3 option descriptions, values and selected value are locked once this is done. Any ideas?

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  • How to create "lock" (stop updating of cells) in Excel?

    - by Oozi
    My question is pretty simple, but one to which I can't really find a solution myself. I use Excel quite frequently, but rarely the fancy stuff. Anyway, to the point: How do I create a dropmenu that will lock certain cells, rows or columns? (by lock I mean unable to change via hand and stops updating itself). Example: A1 = 5 B1 = A1 * 100 Can I "lock" the B1-cell, so that changing A1 will have no effect on B1 (Will remain at value 500)? I would preferably want to be able to "unlock" the cell as well, instead of simply making function into value. Is this possible? Thanks in advance!

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  • How to get record value from LinqDataSource via Code Behind

    - by rockinthesixstring
    I've got a LinqDataSource that retrieves a single record. Protected Sub LinqDataSource1_Selecting(ByVal sender As Object, ByVal e As System.Web.UI.WebControls.LinqDataSourceSelectEventArgs) Handles LinqDataSource1.Selecting Dim BizForSaleDC As New DAL.BizForSaleDataContext e.Result = BizForSaleDC.bt_BizForSale_GetByID(e.WhereParameters("ID")).FirstOrDefault End Sub I'd like to be able to retrieve the values of said DataSource using the Page_Load function. Protected Sub Page_Load(ByVal sender As Object, ByVal e As EventArgs) Handles Me.Load 'Get the right usercontrol' Dim ctrl As UserControl Select Case DataBinder.Eval(LINQDATASOURCE_SOMETHING.DataItem, "AdType") Case 1 : ctrl = DirectCast(Me.FindControl("Default1"), UserControl) Case 2 : ctrl = DirectCast(Me.FindControl("Default1"), UserControl) Case 3 : ctrl = DirectCast(Me.FindControl("ValuPro1"), UserControl) Case 4 : ctrl = DirectCast(Me.FindControl("ValuPro1"), UserControl) Case Else : ctrl = Nothing End Select 'set the control to visible' ctrl.Visible = True End Sub But obviously the code above doesn't work... I'm just wondering if there's a way to make it work. Here is the full markup <body> <form id="form1" runat="server"> <asp:LinqDataSource ID="LinqDataSource1" runat="server"> <WhereParameters> <asp:QueryStringParameter ConvertEmptyStringToNull="true" Name="ID" QueryStringField="ID" Type="Int32" /> </WhereParameters> </asp:LinqDataSource> <uc:Default ID="Default1" runat="server" Visible="false" /> <uc:ValuPro ID="ValuPro1" runat="server" Visible="false" /> </form> </body> </html> Basically what happens is the appropriate usercontrol is enabled and that usercontrol inherits the LinqDataSource and displays the appropriate information. EDIT: It's working now with the code below, however, since I'm really not into hitting the database multiple times for the same info, I'd prefer to get the value from the DataSource. 'Query the database' Dim _ID As Integer = Convert.ToInt32(Request.QueryString("ID")) Dim BizForSaleDC As New BizForSaleDataContext Dim results = BizForSaleDC.bt_BizForSale_GetByID(_ID).FirstOrDefault 'Get the right usercontrol' Dim ctrl As UserControl Select Case results.AdType Case 1 : ctrl = DirectCast(Me.FindControl("Default1"), UserControl) Case 2 : ctrl = DirectCast(Me.FindControl("Default1"), UserControl) Case 3 : ctrl = DirectCast(Me.FindControl("ValuPro1"), UserControl) Case 4 : ctrl = DirectCast(Me.FindControl("ValuPro1"), UserControl) Case Else : ctrl = Nothing End Select

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  • Searching Week-wise/Month-wise record counts(number) and the StartDate+EndDate(datetime) of the Week

    - by Muzaffar Ali Rana
    I have a question in connection to this question earlier posted by me:- http://stackoverflow.com/questions/2452984/daily-weekly-monthly-record-count-search-via-storedprocedure I want to have the Count of Calls on Weekly-basis and Monthly-basis, Daily-basis issue is resolved. ISSUE NUMBER @1:Weekly-basis Count of Calls and Start-Date and End-Date of Week I have searched the Start-Date and End-Date of Week including their individual Count of Calls as well in the below-mentioned query. But the problem is that I could not get the result in one single table, although I have used the Temporary Tables(#TempTable+#TempTable2). Kindly help me in this regards. NOTE:Table Creation commented as for executing more than once. ----- *** TABLE CREATION OF #TempTable & #TempTable2 *** ---------- --CREATE TABLE #TempTable( StartDate datetime,EndDate datetime,CallCount numeric(18,5)) --CREATE TABLE #TempTable2( StartDate datetime,EndDate datetime,CallCount numeric(18,5)) DECLARE @StartDate datetime,@EndDate datetime,@StartDateTemp1 datetime,@StartDateTemp2 datetime,@EndDateTemp datetime,@Period varchar(50); SET @StartDate='1/1/2010'; SET @EndDate='2/28/2010'; SET @StartDateTemp1=@StartDate; SET @StartDateTemp2=DATEADD(dd, 7, @StartDate ); SET @Period='Weekly'; IF (@Period = 'Weekly') BEGIN WHILE ((@StartDate <= @StartDateTemp1) AND (@StartDateTemp2 <= @EndDate)) BEGIN IF((@StartDateTemp1 < @StartDateTemp2 ) AND (@StartDateTemp1 != @StartDateTemp2) ) BEGIN SELECT convert(varchar, @StartDateTemp1, 106) AS 'Start Date', convert(varchar, @StartDateTemp2, 106) AS 'End Date', COUNT(*) AS 'Call Count' FROM TRN_Call WHERE (CallTime = @StartDateTemp1 AND CallTime <= @StartDateTemp2 ); END SET @StartDateTemp1 = DATEADD(dd, 7, @StartDateTemp1); SET @StartDateTemp2 = DATEADD(dd, 7, @StartDateTemp2); END END ISSUE NUMBER @2:Monthly-basis Count of Calls and Start-Date and End-Date of Week In this case, I have the same search, but will have to search the Call Counts plus the Start-Date and End-Date of the Month. Kindly help me in this regards as well.

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  • record output sound in python

    - by aaronstacy
    i want to programatically record sound coming out of my laptop in python. i found PyAudio and came up with the following program that accomplishes the task: import pyaudio, wave, sys chunk = 1024 FORMAT = pyaudio.paInt16 CHANNELS = 1 RATE = 44100 RECORD_SECONDS = 5 WAVE_OUTPUT_FILENAME = sys.argv[1] p = pyaudio.PyAudio() channel_map = (0, 1) stream_info = pyaudio.PaMacCoreStreamInfo( flags = pyaudio.PaMacCoreStreamInfo.paMacCorePlayNice, channel_map = channel_map) stream = p.open(format = FORMAT, rate = RATE, input = True, input_host_api_specific_stream_info = stream_info, channels = CHANNELS) all = [] for i in range(0, RATE / chunk * RECORD_SECONDS): data = stream.read(chunk) all.append(data) stream.close() p.terminate() data = ''.join(all) wf = wave.open(WAVE_OUTPUT_FILENAME, 'wb') wf.setnchannels(CHANNELS) wf.setsampwidth(p.get_sample_size(FORMAT)) wf.setframerate(RATE) wf.writeframes(data) wf.close() the problem is i have to connect the headphone jack to the microphone jack. i tried replacing these lines: input = True, input_host_api_specific_stream_info = stream_info, with these: output = True, output_host_api_specific_stream_info = stream_info, but then i get this error: Traceback (most recent call last): File "./test.py", line 25, in data = stream.read(chunk) File "/Library/Python/2.5/site-packages/pyaudio.py", line 562, in read paCanNotReadFromAnOutputOnlyStream) IOError: [Errno Not input stream] -9975 is there a way to instantiate the PyAudio stream so that it inputs from the computer's output and i don't have to connect the headphone jack to the microphone? is there a better way to go about this? i'd prefer to stick w/ a python app and avoid cocoa.

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  • Linq-to-sql Add item and a one-to-many record at once

    - by Oskar Kjellin
    I have a function where I can add articles and users can comment on them. This is done with a one to many relationship like= "commentId=>ArticleId". However when I try to add the comment to the database at the same time as I add the one to many record, the commentId is not known. Like this code: Comment comment = new Comment(); comment.Date = DateTime.UtcNow; comment.Text = text; comment.UserId = userId; db.Comments.InsertOnSubmit(comment); comment.Articles.Add(new CommentsForArticle() { ArticleId = articleId, CommentId = comment.CommentId }); The commentId will be 0 before i press submit. Is there any way arround not having to submit in between or do I simply have to cut out the part where I have a one-to-many relationship and just use a CommentTable with a column like "ArticleId". What is best in a performance perspective? I understand the underlying issue, I just want to know which solution works best.

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  • Mailing Address is forcing 2nd Record in CSV (DevExpress Controls)

    - by Gerhard Weiss
    My DevExpress CSV export has two lines per record. Rank Score,Prog.,Full Address 63.30 ,JIW ,1234 Whispering Pines Dr , ,Sometown MI 48316 62.80 ,JIW ,9876 Beagle Dr , ,Sometown Twp MI 48382 I would like to change it to one line because I want to do a Word Merge. (Unless Word can merge these two lines back together, which I do not thing it can do) Does the DevExpress XtraGrid ExportToText allow for this? A MemoEdit is being used by the XtraGrid and is initialized using the following code (Noticed the ControlChars.NewLine): Public ReadOnly Property FullAddress() As String Get Dim strAddress As System.Text.StringBuilder = New StringBuilder() If Not IsNullEntity Then strAddress.Append(Line1 + ControlChars.NewLine) If Not Line2 Is Nothing AndAlso Me.Line2.Length > 0 Then strAddress.Append(Line2 + ControlChars.NewLine) End If If Not Line3 Is Nothing AndAlso Me.Line3.Length > 0 Then strAddress.Append(Line3 + ControlChars.NewLine) End If strAddress.Append(String.Format("{0} {1} {2}", City, RegionCode, PostalCode)) If Me.Country <> "UNITED STATES" Then strAddress.Append(ControlChars.NewLine + Me.Country) End If End If Return strAddress.ToString End Get End Property Here is the export to CSV code: Dim saveFile As New SaveFileDialog With saveFile '.InitialDirectory = ClientManager.CurrentClient.Entity.StudentPictureDirectory .FileName = "ApplicantList.csv" .CheckPathExists = True .CheckFileExists = False .Filter = "All Files (*.*)|*.*" End With If saveFile.ShowDialog() = Windows.Forms.DialogResult.OK Then Dim PrintingTextExportOptions As New DevExpress.XtraPrinting.TextExportOptions(",", Encoding.ASCII) PrintingTextExportOptions.QuoteStringsWithSeparators = True ApplicantRankListViewsGridControl.ExportToText(saveFile.FileName, PrintingTextExportOptions) End If

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  • How to call Postgres function returning SETOF record?

    - by Peter
    I have written the following function: -- Gets stats for all markets CREATE OR REPLACE FUNCTION GetMarketStats ( ) RETURNS SETOF record AS $$ BEGIN SELECT 'R approved offer' AS Metric, SUM(CASE WHEN M.MarketName = 'A+' AND M.Term = 24 THEN LO.Amount ELSE 0 end) AS MarketAPlus24, SUM(CASE WHEN M.MarketName = 'A+' AND M.Term = 36 THEN LO.Amount ELSE 0 end) AS MarketAPlus36, SUM(CASE WHEN M.MarketName = 'A' AND M.Term = 24 THEN LO.Amount ELSE 0 end) AS MarketA24, SUM(CASE WHEN M.MarketName = 'A' AND M.Term = 36 THEN LO.Amount ELSE 0 end) AS MarketA36, SUM(CASE WHEN M.MarketName = 'B' AND M.Term = 24 THEN LO.Amount ELSE 0 end) AS MarketB24, SUM(CASE WHEN M.MarketName = 'B' AND M.Term = 36 THEN LO.Amount ELSE 0 end) AS MarketB36 FROM "Market" M INNER JOIN "Listing" L ON L.MarketID = M.MarketID INNER JOIN "ListingOffer" LO ON L.ListingID = LO.ListingID; END $$ LANGUAGE plpgsql; And when trying to call it like this... select * from GetMarketStats() AS (Metric VARCHAR(50),MarketAPlus24 INT,MarketAPlus36 INT,MarketA24 INT,MarketA36 INT,MarketB24 INT,MarketB36 INT); I get an error: ERROR: query has no destination for result data HINT: If you want to discard the results of a SELECT, use PERFORM instead. CONTEXT: PL/pgSQL function "getmarketstats" line 2 at SQL statement I don't understand this output. I've tried using perform too, but I thought one only had to use that if the function doesn't return anything.

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