Create and Destroy NI-DAQ™mx Tasks in Memory

Issue Details

• I am not sure when I should create or destroy NI-DAQmx tasks.
• I am concerned about memory usage when tasks are not cleared after acquisition.
• I see my application slowing down when I use NI-DAQmx tasks inside a loop.

Solution

NI-DAQmx allocates memory when a task is created and releases memory when the task is cleared. Improper handling of task creation inside loops can lead to performance degradation and memory exhaustion.

To prevent these issues, follow these best practices:

• Avoid creating tasks inside loops: Move DAQmx Create Task.vi outside of For Loops or While Loops whenever possible.
• Clear tasks after use: Call DAQmx Clear Task.vi after completing the operation to release allocated resources.
• Reuse tasks when possible: Create the task once and reuse it within the loop instead of creating a new task in every iteration.
• Use unique task names when required: Ensure each task has a unique name to prevent conflicts. DAQmx Create Task.vi returns an error if a task with the same name already exists.
• Monitor loop execution speed: Fast loops that continuously create tasks can quickly consume memory and degrade performance.

Additional Information

Creating and clearing tasks outside looping structures is considered a best practice to avoid unnecessary memory allocation and improve performance. You can see this in action by looking through the shipping examples in the NI Example Finder.

You can also let the NI-DAQmx driver manage its own de-allocation by enabling auto cleanup on the DAQmx Create Task.vi. If the auto cleanup parameter is set to true, the resources allocated in task creation will be freed when the VI completes. If auto cleanup is set to false, the resources will be freed when LabVIEW exits.