Compare Exchange Operation
The compare-exchange operation is a fundamental concept in parallel computing and multi-threading. It atomically compares the value of a variable with a given value, and if they match, it updates the variable with a new value. This operation is used for tasks such as synchronization, implementing locks, and building certain data structures like linked lists or queues in a thread-safe manner. The key takeaway is that compare-exchange ensures atomicity and is crucial for writing concurrent programs.
Java Code
Java provides built-in support for atomic operations through classes like AtomicInteger
. Here’s how you can implement a compare-exchange:
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- We create an
AtomicInteger
calledvalue
and initialize it to 0. compareAndSet(expected, update)
checks ifvalue
is equal toexpected
; if so, it setsvalue
toupdate
.
C++ Code
In C++, std::atomic
can be used for compare-exchange:
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- We declare an
std::atomic<int>
calledvalue
. compare_exchange_strong(expected, update)
comparesvalue
toexpected
and updates it if they match.
Python Code
Python’s threading
library doesn’t natively support atomic compare-and-exchange, but you can use locks to simulate this behavior:
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- A variable
value
is declared and initialized to 0. - We use
threading.Lock()
to ensure that the comparison and update are atomic.
In all three implementations, the basic idea remains the same: compare a value atomically and update it if the condition is met. This serves as a foundation for more complex operations in multi-threaded programming.