How Do Different Memory Ordering Options Impact Multithreaded Program Execution?

Unlocking the Nuances of Memory Ordering

In the realm of multithreaded programming, memory ordering plays a pivotal role in ensuring data coherence among threads. The concept of memory ordering revolves around the synchronization of memory accesses, both atomic and non-atomic, to maintain a consistent program execution.

To delve deeper into this subject, let's examine the different memory ordering options available in various languages:

1. memory_order_relaxed:
Similar to a bare minimum, relaxed ordering provides no additional synchronization guarantees beyond atomicity. This lack of ordering enables compilers to perform aggressive optimizations, allowing the reordering of memory operations around the atomic operation.

2. memory_order_sequentially_consistent:
Diametrically opposed to relaxed ordering, sequentially consistent ordering imposes strict ordering on both atomic and non-atomic memory operations. This rigid synchronization ensures that operations appear in the exact order they were executed in the program, mirroring sequential program execution.

3. memory_order_release:
Release ordering serves to prevent the reordering of non-atomic stores following an atomic operation. This guarantees that subsequent threads attempting to read the modified variable will observe the updated value first before any non-atomic stores that occurred prior to the atomic operation.

4. memory_order_acquire:
Acquire ordering, in contrast, inhibits the reordering of non-atomic loads preceding an atomic operation. This ensures that reads made after the atomic operation will reflect the updated value, even if non-atomic stores occurred after the atomic operation.

5. memory_order_acq_rel:
This ordering combines the guarantees of both acquire and release orderings, preventing reordering of non-atomic operations both before and after an atomic operation.

6. memory_order_consume:
Consume ordering is similar to acquire ordering, but with a narrower scope. It only enforces synchronization on dependent data, offering potential performance benefits over acquire ordering.

The above is the detailed content of How Do Different Memory Ordering Options Impact Multithreaded Program Execution?. For more information, please follow other related articles on the PHP Chinese website!