Multithreading DotNet4 & VB2010
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Thread: Multithreading DotNet4 & VB2010

  1. #1
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    Multithreading DotNet4 & VB2010

    Hey guys,

    And so I decided to make a multithreaded application :'(

    I am new to multiple threads - so my problem is this...

    4 Threads
    1 Array of lets say 100 strings

    How do I make the 4 threads access the same array - also, once one string has been used(read) - it will be removed by a function that I have written already.

    So the problem I'm experiencing is that when the 1st thread removes the string from the array at that specific stage the 3rd might be accessing the array and the string returned from the array = nothing...

    Any ideas?

  2. #2
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    Re: Multithreading DotNet4 & VB2010

    This is a Loaded Question..

    so before answering, a few questions...

    #1: what sort of processing are you doing on this array of strings?

    #2: How long does this processing take per iteration?

    #3: How CPU intensive is this processing ?
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  3. #3
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    Re: Multithreading DotNet4 & VB2010

    Right - thank you for pointing out those points

    The array is used as a hyperlink collector - I'm writing a kind of spider for research and what needs to be done is as follow.

    The array contains hyperlinks, it needs to be sorted which is easy through Array.Sort(Array)
    Then the douples needs to be removed - also easy by using Array.BinarySearch(Array, Value)
    Then removing the entry, I have written a function to do that.

    So now the problem - testing the link and removing it when there is success and inserting it to another array.
    This is where the multiple threads come in.

    Processing time depends on response time.

    Not so much CPU intensive, if list was larger yes... Not at the moment.

  4. #4
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    Re: Multithreading DotNet4 & VB2010

    Spiders are not Well Liked.... And Many webmasters(Like myself) Block Spider IP's & agents..

    SO .. I'll Ask you not to post any of the spider code.. However with the Array i'll help you...

    Note: This is Few of many ways to solve..

    #1 : Split the Array into 4 (Thread 1 works with 1-25, #2 with 26-50, etc)

    #2 : Create a second Boolean array to mirror the first... loop through the Array, testing the Matching Bool and if False, set to true and process this one...

    #3 : Use Prefixing on the strings to mark processed strings .. Web address starts with 'HTTP' so prefixing with a number or such can work (testing for this is easy)..
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  5. #5
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    Re: Multithreading DotNet4 & VB2010

    Hehe, ye I can understand why you do that
    So no spider code here

    I did think of splitting the array into four - though the coding complexity increases.
    The second bool array is an idea - will try it for a test.
    The prefix idea - almost the same as the bool idea, but at least one array less... Also will try

    Thanks for the ideas - it was staring me right in the face -=facepalm=-

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