CLAD Timing, Synchronization & Parallel Execution 3

Question 1

In LabVIEW's dataflow programming model, two nodes on the block diagram execute in parallel when:

Accepted Answer

There is no data dependency connecting them

Answer

LabVIEW's dataflow model executes nodes as soon as all their input data is available; nodes with no data dependency between them are free to run simultaneously on separate threads.

Question 2

Which LabVIEW structure is specifically designed to automatically distribute loop iterations across multiple processor cores for parallel execution?

Accepted Answer

Parallel For Loop

Answer

The Parallel For Loop structure divides its iteration space and dispatches groups of iterations to available CPU cores concurrently, enabling true data-parallel execution.

Question 3

For a Parallel For Loop to produce correct results, which requirement must the loop body satisfy?

Accepted Answer

No iteration may depend on data computed by another iteration of the same loop

Answer

Because iterations run concurrently in a Parallel For Loop, any iteration that reads data written by another parallel iteration risks a race condition; iterations must be fully independent.

Question 4

The 'Occurrence' synchronization primitive in LabVIEW is most commonly used to:

Accepted Answer

Signal an event from one executing task to another without passing any data

Answer

An Occurrence acts as a lightweight flag: one task calls Set Occurrence to signal it, and another task blocks on Wait on Occurrence until the signal arrives, with no data payload transferred.

Question 5

When two parallel While Loops both read from and write to the same Global Variable without any synchronization, the behavior is:

Accepted Answer

Indeterminate because unguarded reads and writes from parallel threads can interleave unpredictably

Answer

Global Variables in LabVIEW are not thread-safe; without an external locking mechanism such as a Semaphore or Functional Global, parallel loops can observe stale or partially written values.

CLAD Practice Test

CLAD Practice Test

CLAD Timing, Synchronization & Parallel Execution 3