NCNN_XADD should return int

[00liujj]

ncnn/src/allocator.h

Line 92 in 6f1b0b0

static inline void NCNN_XADD(int* addr, int delta) { int tmp = *addr; *addr += delta; return tmp; }

[PapaMadeleine2022]

do not understand this function. return tmp? rather than *addr

[nihui]

That is how compare and exchange works.

[PapaMadeleine2022]

@nihui Thanks. Another confusing place. Let refcount pointer point the last+1 position(last position is for the last item of the Mat) ?

[nihui]

It is fine to make the refcount integer live on its own memory heap.
When the memory is allocated, the mat content data and refcount are allocated together.
We do this as we can save one malloc invocation, resulting less heap fragments.

[PapaMadeleine2022]

@00liujj thanks.

That is how compare and exchange works.

When I see the line here, I finally understand the meaning of NCNN_XADD function. This design is great! Thanks.

[PapaMadeleine2022]

It is fine to make the refcount integer live on its own memory heap.
When the memory is allocated, the mat content data and refcount are allocated together.
We do this as we can save one malloc invocation, resulting less heap fragments.

thanks for your explanation.