Interesting!
I get the same result, ie an infinite loop, with the CPU at 100%
Some things I noticed:
- Changing the for-loops to 100 or 10 doesn't help.
- Changing the atomicOp from "+=" to just "+" makes it work (although the
account doesn't get changed)
- Adding a Thread.sleep(1000) in one of the for-loops, before the call to
atomic-op, makes it all work with "+=" as well
By looking at the code in atomic.d it looks the "+="-operator ends up here:
// L#131..:
T get, set;
do
{
get = set = atomicLoad!(msync.raw)( val );
mixin( "set " ~ op ~ " mod;" );
} while( !cas( &val, get, set ) );
return set;
And I suppose the cas()-function never returns true?
I don't know how atomic is supposed to work, so I'm not sure if it's a bug or
not. I'm no expert with D, or threading for that matter, so I don't know. (I'm
just an expert guesser : )
I guess bug!
BR
/HF
Benjamin Thaut Wrote:
> I recently read the book "the D programming language" and wanted to try
> out a few of the multithreaded examples pointed out in this book. I
> tried to write a version of the bank account example using the atomicOp
> from core.atomic. But when I compile it, it never finishes, it just gets
> stuck in a endless loop inside atomic.d I think.
> Here is the code:
>
> import std.stdio;
> import std.concurrency;
>
> enum Messages {
> GO
> }
>
> shared class Account {
> private float amount = 0;
>
> float getAmount() const {
> return amount;
> }
>
> void change(float change){
> atomicOp!"+="(amount,change);
> }
> }
>
> shared Account bank = null;
>
> void otherThread(Tid father){
> send(father,Messages.GO);
> for(int i=0;i<1000;i++)
> bank.change(-100);
> }
>
> void main(string[] args)
> {
> bank = new Account();
> spawn(&otherThread,thisTid);
> receiveOnly!(Messages)();
> for(int i=0;i<1000;i++)
> bank.change(+100);
> writefln("Program finished. Amount is %s",bank.getAmount());
> }
>
> If you could please point out what I did wrong I would be very glad. If
> I did not do anything wrong, I don't quite understand whats the exact
> problem because the code inside atomic.d looks good (at least at my
> level of understanding)
>
> --
> Kind Regards
> Benjamin Thaut
