How to distinguish a race condition problem in multithreaded work from a situation where the result depends on the unpredictable order of operations?

A race condition occurs when multiple threads access shared data simultaneously without proper synchronization, and the final result depends on the order of execution, leading to unpredictable behavior.

You can distinguish it from simply unpredictable operation order as follows:

• Race conditions: involve shared mutable resources, and lack of synchronization leads to errors (e.g., incorrect counter value).
• Unpredictable order: operations are independent, and their order does not affect correctness but may influence performance or output.

Example of a race condition:

var counter = 0
DispatchQueue.concurrentPerform(iterations: 1000) { _ in
    counter += 1 // Unsynchronized modification
}
print(counter) // Might be less than 1000 due to race condition

Adding synchronization (e.g., via DispatchQueue.sync or NSLock) makes the result predictable.

Thus, if an error occurs due to concurrent access to shared data without protection — it is a race condition.