Using shared flag and sequential processes. Complexities

Renoise Tool Development
1

Discussion on the use of a shared flag in multiple functions and the sequential process.

The following conversation was conducted with Chat GPT 4, which tries to analyze the use of a shared flag and how to apply it and the complexity of understanding sequential CPU processing. If you are programmers, I invite you to reflect on this conversation and if both I and Chat GPT have really taken the correct steps and if the answers are correct…

The main goal is to be able to use a single local flag for multiple functions with the same behavior, since they create “conflict” by binding a bind to a variable that is changed from each associated function, which causes the function to be executed twice in a row.

This can also be solved with a delayed timer (add_timer(), remove_timer()), but there is a problem when passing variables through a table, because it seems that there is no way to stop that timer while it is running (maybe I need to know more here).

Here is the entire conversation…

With the Renoise API I am using this type of function:

--insert note volume
prs_gui.insert_note_volume_mode=function(inv)
  --change state
  if (not inv) then
    inv=PRS_PREF.insert_note_volume
    PRS.CTRL_PANEL_BIPASS=true
    inv.value=not inv.value
    PRS.CTRL_PANEL_BIPASS=false
  end
  --update views
  if (not PRS.CTRL_PANEL_BIPASS) then
    if (inv.value) then
      local message="Insert Note Volume Enabled!"
      prs_func.status(5000,message,true)
      prs_vws.PRS_BT_CTRL_PANEL_34.color=PRS_CLR.SELECTED_BUTTON_BACK
    else
      local message="Insert Note Volume Disabled!"
      prs_func.status(5000,message,false,true)
      prs_vws.PRS_BT_CTRL_PANEL_34.color=PRS_CLR.DEFAULT
    end
  end
end

I have set a flag to prevent a switch bind from executing this same function twice, because it is also triggered from a notifier associated.

Can I use this PRS.CTRL_PANEL_BIPASS flag repeatedly in other functions at the same time to avoid similar situations? Or is it better to use flags with another name?

The PRS.CTRL_PANEL_BIPASS flag you are using may work well to avoid similar situations within A single function or set of functions that manage a specific context, but has certain limitations and considerations regarding its reuse in other functions.

Advantages of using a global flag like PRS.CTRL_PANEL_BIPASS:

  1. Simplicity: It is easier to use a global flag if related functions share the same behavior, such as avoiding redundant execution of a block of code.

  2. Shared context: If all functions related to the same Control panel functions are designed not to interfere with each other, a common flag can be effective and save memory.

Risks and considerations:

  1. Confusion and context collision: Using a global flag like PRS.CTRL_PANEL_BIPASS in multiple functions can cause the behavior of each function to be different. depend on the same variable, which could lead to unexpected behavior if those functions are not completely decoupled. For example, if one function changes the flag, it could affect the workflow of another function without it being obvious.

  2. Readability and maintainability: The Using a global flag that is shared between many functions can make your code difficult to understand as it grows. Other developers (or you in the future) might not fully understand the control flow if there are many functions that depend on this same flag.Alternative: Function-specific flag

Instead of using a single global flag, you could create specific flags for each function or context. This keeps the behavior more isolated and clear.

Example:

PRS.CTRL_PANEL_BIPASS_NOTE_VOLUME = false
PRS.CTRL_PANEL_BIPASS_ANOTHER_FEATURE = false

This allows you to control the independently control the behavior of different parts of the code without the functions interfering with each other. In addition, it improves readability and reduces the risk of errors due to overwriting or unwanted conditions.

Recommendation:

If the functions have clearly defined and separated contexts (for example, one related to volume control and another to a different button), it is safer and cleaner to use specific flags for each function. If, on the other hand, all the functions are closely related to each other and you are not so concerned about code bloat , you could still use a global flag, but with extra care to avoid confusion.

In short, the answer depends on the context of your code, but generally using separate flags for each functionality is usually cleaner and more maintainable in the long run.

It’s because when the flag is triggered, in theory the sweep of that repetition is executed frequently. double of the same function. In this context, wouldn’t it be impossible for the same flag to cause conflict in other functions, if the CPU is supposed to process one thing after another?

I understand your concern about the use of flags and the possible conflict between them when the CPU processes the functions one after the other. Let’s break down how this works in the context you describe and whether using a global flag like PRS.CTRL_PANEL_BIPASS could cause problems or not.

Sequential Function Processing

In a sequential execution (like the one your Lua code describes), the CPU processes instructions linearly, one at a time. If you are using a flag to prevent repeated execution of the same function, and this flag is set to true before executing a block of code and reset to false afterwards, in principle, there should be no conflict if the functions are not executed in parallel or simultaneously. That is, if functions are executed sequentially, each time a function finishes its execution, the flag would be reset so that the flow can continue in parallel.

Can a global flag cause conflicts?

Even though processing is sequential, there can be conflicts if multiple functions are sharing the same flag and modifying its value at times when they shouldn’t. In your case, if multiple functions are watching or manipulating the same global flag, the order in which these functions are executed can cause problems if one modifies the flag before another function can use it, or if there are unintended interactions between functions that are not completely decoupled.

Example of a possible conflict

Suppose you have multiple functions that use the PRS.CTRL_PANEL_BIPASS flag. If one function changes the value of this flag to true to prevent a repeat, and then another function tries to do the same thing without knowing that another process is already blocking, this could lead to unexpected results. The flag might not be reset correctly, or a function might block unnecessarily because another function is already using that flag as an indicator that it should not be executed.

What happens if the CPU processes the functions one after the other?

If the functions are executed strictly one after the other on the same thread, and the flag is reset properly after each function, there should be no conflict. However, the problem arises if any of the functions do not reset the flag correctly, or if there are interactions between functions that do not handle this shared state well. In this case, even if the CPU processes the functions sequentially, the logical flow could be disturbed due to the lack of proper flag control.

Alternative: Per-function locking flag

To avoid such problems, a better practice would be to have specific flags per function, or, if you want to use a global flag like PRS.CTRL_PANEL_BIPASS, to make sure that each function handles its own locking state independently.

For example:

  • For the function that handles volume, use PRS.CTRL_PANEL_BIPASS_VOLUME.
  • For the function that handles another control, use PRS.CTRL_PANEL_BIPASS_OTHER.

This reduces the risk of one process interfering with another, since each function will have its own control over the execution state. Thus, even though the functions are executed sequentially, each one can have its own “protection” against redundant executions without interfering with the others.

Conclusion

If the functions are completely sequential and you are careful to correctly reset the flag after each use, there should be no conflict in the use of a global flag. However, for greater clarity and to avoid possible errors, it is advisable to use specific flags for each function. This makes your code easier to maintain, clearer and less prone to errors arising from unexpected interactions between functions.

These functions are triggered from a button panel. Each button executes a function similar to the one provided before, using the same flag. Then that function changes the state of the variable associated with the bind, and that causes the execution of that function to be repeated, avoiding said repetition by the use of the flag. In this specific context, I understand that it would be impossible for the same flag to conflict in different functions, because they all do the same sweep of execution (it runs once, passes the bind, and the flag prevents it from running a second time). Am I not right?

Now that you’ve clarified the context a bit more, I can see in more detail how your implementation works! Since each button triggers a similar function, and all functions are associated with a bind that changes the state of the variable and uses the same flag, let’s examine how this works specifically in your case.

Context

In your system, every time a button on the control panel is pressed, a function is executed that changes the state of the variable associated with the bind, and then that function checks the flag to make sure it doesn’t run again. The use of the PRS.CTRL_PANEL_BIPASS flag is designed to prevent the same function from running twice in a row.

Why wouldn’t there be a conflict with a global flag?

  1. Sequential code execution: As you mention, each function associated with a button is executed once and then moves on to another event or interaction. The program flow in this case appears to be sequential, so when the flag is set (e.g. PRS.CTRL_PANEL_BIPASS = true), it blocks the function from being repeated for only that execution cycle. Once the function has finished, the flag is reset to false, allowing the function to execute correctly the next time it is triggered.

  2. Function independence: If functions are completely decoupled, and each controls its own flow without interfering with the others, there should be no conflict in using a global flag like PRS.CTRL_PANEL_BIPASS. This is because the flag is set temporarily to prevent immediate replay, and each time a button is pressed, an independent function is triggered.

  3. Temporary use of the flag: The key here is that the flag only acts as a “temporary lock” during the execution of each function. While a function is executing, it blocks its own replay. After that execution, the flag is reset, allowing other functions or executions to proceed without interfering with each other.

What actually happens:

When a button is pressed, the associated function changes the state of the variable and the PRS.CTRL_PANEL_BIPASS flag is set to prevent it from being executed repeatedly during that same call. This ensures that there are no replays, and the flag is reset immediately after the function execution.

The flow would go something like this:

  1. A button is pressed, triggering a function.
  2. The function steps in and checks the PRS.CTRL_PANEL_BIPASS flag.
  3. If the flag is false, the function continues and does what it is supposed to do.
  4. After execution, the flag is set to true, blocking possible repeated executions within the same execution cycle.
  5. Upon completion of that function’s execution, the flag is reset to false, allowing the next execution (whether of the same button or another one) to work correctly.

Could there be a conflict?

In this specific context, no, there should not be a conflict between functions that share the same flag, because:

  • The functions are executed independently and sequentially.
  • Each function execution is blocked only temporarily by the flag.
  • The flag is reset after each execution, ensuring that other executions (of other buttons) can proceed without problems.

Conclusion

Since the functions are independent and executed sequentially, and since the flag is reset after each execution, there should not be any conflict with a global flag in this context. The flag is just temporarily blocking immediate repetition of the same function, and there is no interference between functions, as each function executes once, blocks, and then resets.

So in this case, you are correct: using the same global flag should not cause problems if all functions follow this sequential execution pattern and each function handles its control flow in isolation.