Software Portability
When we talk about software portability, we usually come up with 2 categories
- portable software - cross-platform software, which can be transport from platfrom to platform
- port software - software adopt to one platform
There are four dimensions determining software portability
- Hardware
- Language
- Libraries
- Operatio System / Interfaces
For example LP64 and ILP32 are two different C Language Data Type Models.
If we define
size_t a; in ILP32, its size will be 32 bits. But if we define it in LP64, it will be 64 bits.
As a result, if we want to develop a portable software accross platforms, we have to think about how to overcome these variations.
Atomics
Atomic is a physics idea, in software development point of view, it means to make operations indivisiable/uninterruptible. The reason is that sometimes, multiple threads will interrupt one operation when it is executing in multi-core situations.
For example:
if (x == 0)
{
x += 1;
}
It is possible that other thread interruption will happen between the addition and assignment process.
To avoid this problem, we can use intrinstics: e.g.
__atomic_load_n
__atomic_store_n
An atomic operation can both constrain code motion and be mapped to hardware instructions for synchronization between threads (e.g., a fence).