Traverse non-binary treelike structure from TwinCat with multiple Threads in c#

Question

I am trying to optimize a search algorithm I am using to find marked Symbols in TwinCat 3 through the ADS Interface. The question is not TwinCat related so don't get scared off yet.

The problems: Symbols are not loaded at once. I think the TwinCatAds library use lazy loading. Symbols have treelike structure of non-binary not balanced tree.

The solution: You can open more than one stream to ADS. And handle the the streams in multiple threads.

The question is, I divide the first level of symbols by the number of the processor cores. So Because the tree is unbalanced some of the Threads finish faster than the others. Because of this I need a nicer solution how to divide the work between the threads.

PS: I can't use the Parallel.ForEach(). Because of the streams it results in the same or greater time amount as the single thread solution.

My test code looks looks this, it just counts all Symbols of a huge Project.

using TwinCAT.Ads;
using System.Threading;
using System.IO;
using System.Diagnostics;
using System.Collections;


namespace MultipleStreamsTest
{
class Program
{
    static int numberOfThreads = Environment.ProcessorCount;
    static TcAdsClient client;
    static TcAdsSymbolInfoLoader symbolLoader;
    static TcAdsSymbolInfoCollection[] collection = new TcAdsSymbolInfoCollection[numberOfThreads];
    static int[] portionResult = new int[numberOfThreads];
    static int[] portionStart = new int[numberOfThreads];
    static int[] portionStop = new int[numberOfThreads];

    static void Connect()
    {
        client = new TcAdsClient();
        client.Connect(851);
        Console.WriteLine("Conected ");
    }
    static void Main(string[] args)
    {
        Connect();
        symbolLoader = client.CreateSymbolInfoLoader();
        CountAllOneThread();
        CountWithMultipleThreads();
        Console.ReadKey();
    }        
    static public void CountAllOneThread()
    {
        Stopwatch stopwatch = new Stopwatch();
        int index = 0;
        stopwatch.Start();
        Console.WriteLine("Counting with one thread...");
        //Count all symbols
        foreach (TcAdsSymbolInfo symbol in symbolLoader)
        {                
            index++;
        }
        stopwatch.Stop();
        //Output
        Console.WriteLine("Counted with one thred " + index + " symbols in " + stopwatch.Elapsed);
    }
    static public int countRecursive(TcAdsSymbolInfo symbol)
    {
        int i = 0;
        TcAdsSymbolInfo subSymbol = symbol.FirstSubSymbol;
        while (subSymbol != null)
        {
            i = i + countRecursive(subSymbol);
            subSymbol = subSymbol.NextSymbol;
            i++;
        }
        return i;
    }
    static public void countRecursiveMultiThread(object portionNum)
    {
        int portionNumAsInt = (int)portionNum;
        for (int i = portionStart[portionNumAsInt]; i <= portionStop[portionNumAsInt]; i++)
        {
                portionResult[portionNumAsInt] += countRecursive(collection[portionNumAsInt][i]);//Collection Teil 
        }
    }
    static public void CountWithMultipleThreads()
    {
        Stopwatch stopwatch = new Stopwatch();
        int sum = 0;
        stopwatch.Start();
        Console.WriteLine("Counting with multiple thread...");
        for (int i = 0; i < numberOfThreads; i++)
        {
            collection[i] = symbolLoader.GetSymbols(true);
        }
        int size = (int)(collection[0].Count / numberOfThreads);
        int rest = collection[0].Count % numberOfThreads;
        int m = 0;
        for (; m < numberOfThreads; m++)
        {
            portionStart[m] = m * size;
            portionStop[m] = portionStart[m] + size - 1;
        }
        portionStop[m - 1] += rest;

        Thread[] threads = new Thread[numberOfThreads];
        for (int i = 0; i < numberOfThreads; i++)
        {
            threads[i] = new Thread(countRecursiveMultiThread);
            threads[i].Start(i);
            Console.WriteLine("Thread #" + threads[i].ManagedThreadId + " started, fieldIndex: " + i);
        }
        //Check when threads finishing:
        int threadsFinished = 0;
        bool[] threadFinished = new bool[numberOfThreads];
        int x = 0;
        while (true)
        {
            if (threads[x].Join(10) && !threadFinished[x] )
            {
                Console.WriteLine("Thread #" + threads[x].ManagedThreadId + " finished ~ at: " + stopwatch.Elapsed);
                threadsFinished++;
                threadFinished[x] = true;                    
            }
            x++;
            x = x % numberOfThreads;
            if (threadsFinished == numberOfThreads) break;
            Thread.Sleep(50);
        }            
        foreach (int n in portionResult)
        {
            sum += n;
        }
        sum += collection[0].Count;
        stopwatch.Stop();
        //Output
        Console.WriteLine("Counted with multiple threds in Collection " + sum + " symbols " + " in " + stopwatch.Elapsed);
        for (int i = 0; i < numberOfThreads; i++)
        {
            Console.WriteLine("#" + i + ": " + portionResult[i]);
        }
    }
}
}

The console output:

If you trying to run the Code use TwinCat.Ads Version 4.0.17.0(that i am using). They broke something in the new version that is available with NuGet.

J.R. · Accepted Answer · 2016-10-27 14:20:14Z

1

Make a thread pool and keep track of threads running and idling status. At each branch check if there is idling threads, if there is assign thread to sub branch.

answered Oct 27, 2016 at 14:20

J.R.

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