Re: difference between x.atomicOp!"+="(1) and atomicFetchAdd(x, 1)?

[mw via Digitalmars-d-learn]

On Thursday, 10 November 2022 at 18:30:16 UTC, Paul Backus wrote:

On Thursday, 10 November 2022 at 17:04:31 UTC, mw wrote:

Hi,

Anyone can help explain what is the difference between 
x.atomicOp!"+="(1) and atomicFetchAdd(x, 1)?


Looking at the source in druntime, `atomicOp!"+="` forwards to 
`atomicFetchAdd` internally, so they should have the same 
behavior.


Thanks! Indeed:

https://github.com/dlang/dmd/blob/master/druntime/src/core/atomic.d#L582

(source is always your best friend :-)

and looks like atomicFetchAdd is more fundamental:

```
return cast(T)(atomicFetchAdd(val, mod) + mod);
```

Re: difference between x.atomicOp!"+="(1) and atomicFetchAdd(x, 1)?

[Paul Backus via Digitalmars-d-learn]

On Thursday, 10 November 2022 at 17:04:31 UTC, mw wrote:

Hi,

Anyone can help explain what is the difference between 
x.atomicOp!"+="(1) and atomicFetchAdd(x, 1)?


Looking at the source in druntime, `atomicOp!"+="` forwards to 
`atomicFetchAdd` internally, so they should have the same 
behavior.

difference between x.atomicOp!"+="(1) and atomicFetchAdd(x, 1)?

[mw via Digitalmars-d-learn]

Hi,

Anyone can help explain what is the difference between 
x.atomicOp!"+="(1) and atomicFetchAdd(x, 1)?


From the doc, their return values are different

atomicOp
Performs the binary operation 'op' on val using 'mod' as the 
modifier.

Returns:
The result of the operation.


atomicFetchAdd
Atomically adds mod to the value referenced by val and returns 
the value val held previously. This operation is both lock-free 
and atomic.

Returns:
The value held previously by val.


Apart from this, any other difference, esp in a multithreaded 
program? Are they the same? Is atomicOp also lock-free?


Thanks.