iTask - how to use variables as parameters to TTask procedure

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• How to wait for multiple threads to complete and reuse them?

  I have a C++ program that tries to process each line of array in parallel, and after one line completely finishes, it moves on to the next line. My current program creates a thread for each line of array, and join them after usage. But it seems that the program is wasting a lot of time on creating/closing threads.

  Is there a way to create those threads just for one time, and for each line they wait for the slowest thread to finish and then execute functions for the next line?

  Here is my sample code:

  #include <iostream>
  #include <thread>
  using namespace std;
  #define THREAD 5
  int arr[2][10000];
  void update_arr(int i, int j_s, int j_to){
      for (int j = j_s; j <= j_to; j++)
          arr[i%2][j]= arr[(i-1)%2][j]+2*arr[(i-1)%2][j-1];
  }
  
  int main(){
      for (int i = 0; i < 10000; i++) arr[0][i] = 1;
      for (int i = 1; i <= 10000; i++){
          thread t[THREAD];
          for (int ii = 0; ii < THREAD; ii++)
              t[ii] = thread(update_arr, i, ii * 10000 / THREAD, (ii+1) * 10000 / THREAD - 1);
  
          for (int ii = 0; ii < THREAD; ii++)
              t[ii].join();   
      }
      cout<<arr[1][9999]<<endl;
  }
  
• How to "keep main thread running" even though routine has "runtime error" occurred in Golang?

  I am new to Goland and I did Java in the past. I've written a Golang function to calculate the integer number part of the result. What I am thinking is using a timer to do the calculation and generate the random number. But one problem I met is if the routine has some error, the main thread will stop. Is there any way to keep the main thread running? Even though there are errors in routine?

  Below is the code for test:

  func main() {
      ticker := time.NewTicker(1*1000 * time.Millisecond)
      for _ = range ticker.C {
          rand.Seed(time.Now().Unix())
          divisor := rand.Intn(20)
          go calculate(divisor)
      }
  }
  
  func calculate(divisor int){
      result:= 100/divisor
      fmt.Print("1/"+strconv.Itoa(divisor)+"=")
      fmt.Println(result)
  }
  

  As the error handling for Golang really confused me, as what I am thinking is the error occurs in the "thread", the main function is just responsible to create the thread and assign task, it should never mind whether there are exceptions occurs in the "threads" and main should always keep going. If I do this in Java, I could use try catch to surround with

  try{
      result = 1/divisor;
  }
  catch(Exception e){
      e.printTrace();
  }
  

  even every time I give divisor a 0 value in a separate thread, the main progress will not exit, but for Golang, I think

  go calculate(divisor)
  

  is opening a new "thread" and run calculate inside the "thread", but why the main progress will quit. Is there any possible method to prevent the main progress to quit?

  Thanks.
• How does the android split screen feature work on an OS level?

  I want to understand the underlying the concept of multitasking used in this split-screen functionality.Are they two different processes with constant context switches between them?

  I recently read about multitasking in Operating Systems and was intrigued by this functionality in Android. Being new to how the internals of multi-threading works, please help me understand these concepts. :-)
• C callback function crash on object pascal

  I'm creating a C dll like below.

  #ifdef TEST_EXPORTS
  #define TEST_API __declspec(dllexport)
  #else
  #define TEST_API __declspec(dllimport)
  #endif
  
  #ifdef __cplusplus
  extern "C" {
  #endif
      /* fun accept an argument status_callback which is a function pointer*/
      TEST_API void fun(void(*status_callback)(int));
  #ifdef __cplusplus
  }
  #endif
  

  and fun is implemented as:

  void fun(void(*status_callback)(int)) {
     status_callback(0);
  }
  

  When using this dll on object pascal with delphi xe like below I got a crash with an access violation at the address of the callback function

  type
   TStatusCallBack = procedure( Value: Integer ); stdcall;
   T_fun = procedure(cb : TStatusCallback );
  
  procedure BCallBack( Value: Integer ); stdcall;
  begin
     BStatus := value;
  end;
  
  begin
   _fun(BCallBack);
  end;
  

  Instantiation code:

  DLLHandle := LoadLibrary( ‘mylib.dll’ );
  if (DLLHandle > HDLL_ERROR) then
  begin
    _fun := T_fun(GetProcAddress( DLLHandle, 'fun');
  end;
  

  What is the issue? Since I'm a noobie to C any comments??
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  I try to create a form with a custom visualisation, but I can't get the simplest drawing methods of TCanvas to work. In the following example, I can see only the filled rectangle, but no line and no arc:

  procedure TEditorPanel.FormPaint(Sender: TObject; Canvas: TCanvas; const ARect: TRectF);
  var
    center, radius: TPointF;
    rect: TRectF;
  begin
    with Canvas do
    begin
      Fill.Color := TAlphaColors.White;
      FillRect(RectF(0, 0, Width, Height), 0, 0, AllCorners, 1);
  
      center := PointF(200, 200);
      radius := PointF(40, 40);
  
      Stroke.Color := TAlphaColors.Red;
      Fill.Color := TAlphaColors.Blue;
      DrawLine(center, radius, 1);
      DrawArc(center, radius, 0, 90, 1);
  
      rect := RectF(10, 10, 100, 100);
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  What am I missing?
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  I'm using a TShellListView component inside my program with my own popup menu. I want to implement a "Open" feature to open the selected file like I can open it from the Windows Explorer.

  Is ExecuteCommand the right way for this? If yes, how does it work. On my way nothing happens:

  var
    ListView: TShellListView;
    Handled: Boolean;
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    ...
    Handled := False;
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  i have two methods: First function always running and get data from some service while response not empty. Second function work with data from first method. I want to call second function when first function returns first success request, and stop second function after working with first method get last data, how can i do it? async or i need using threads?
• Schedulling a task to run silently

  I have scheduled a task to run multiple times a day which calls a .reg file.

  Whilst it runs without any problem, I have to accept two warnings before it executes each time.

  Is there anyway to have it execute without warning prompts?

  It is set to run with highest privileges and hidden.

  The OS is Windows 10.

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• Parallel calls to Web API using await/async

  We have a Web API xyz to which we can only make asynchronous calls. We have asynchronous method CallAPI which in turns calls the API xyz and provides us the response asynchronously. We want to make some 100 calls to that endpoint xyz by invoking CallAPI Method. I tried to use below to do the same but not sure if it is the best way or if there would be any implications with this in future. Any help or any suggestions to improve would be very useful and appreciated.

  await Entities.ParallelForEachAsync(async entity =>
  {
      var apiResponse = await CallAPI(x, y);
  
      if (apiResponse != null)
      {
          entity.Student = apiResponse;
          PersonList.Add(new Person(entity));
      }
  }, maxDegreeOfParalellism: 10);