CppMem – An Overview
CppMem is an interactive tool for exploring the behavior of small code snippets of the C++ memory model. No, it should have to be in the toolbox of each programmer who deals seriously with the memory model.
Author Archive for: admin
Entries by Rainer Grimm
Relaxed Semantics
The relaxed semantics is the end of the scale. The relaxed semantic is the weakest of all memory models and guarantees that the operations on atomic variables are atomic.
Acquire-Release Fences
Acquire and release fences guarantee similar synchronization and ordering constraints as atomics with acquire-release semantics. Similar because the differences are in the details.
Fences are Memory Barriers
The key idea of a std::atomic_thread_fence is to establish synchronization and ordering constraints between threads without an atomic operation.
Acquire-Release Semantics – The Typical Misunderstanding
A release operation synchronizes-with an acquire operation on the same atomic variable. So we can easily synchronise threads, if … . Today’s post is about the if.
100 Posts Anniversary – Quo vadis Modernes C++?
As you may know, I translate in this blog the posts from my German blog into English. My German blog has the 100 posts anniversary. So I started a poll for the next new main topic.
Transitivity of the Acquire-Release Semantic
A release operation synchronizes with an acquire operation on the same atomic variable and establishes, in addition, ordering constraints. These are the components to synchronize threads in a performant way in case they act on the same atomic. But how can that work, if two threads share no atomic variable? We want no sequential consistency […]
memory_order_consume
std::memory_order_consume is the most legendary of the six memory models. That’s for two reasons. On the one hand, std::memory_order_consume is extremely hard to get. On the other hand – that may change in the future – no compiler supports it.
Acquire-Release Semantic
With the acquire-release semantics, the memory model gets very thrilling. Because now, we do not have to reason about the synchronization of threads, we have to reason about the synchronization of the same atomic in different threads.
Sequential Consistency applied
I have introduced In the post Sequential Consistency the default memory model. This model, in which all operations in all threads take place in a global time clock, has a big advantage but also a significant disadvantage.