new D2.0 + C++ language

[Sergey Gromov]

Wed, 18 Mar 2009 13:48:55 -0400, Craig Black wrote:

> bearophile Wrote:
> 
>> Weed:
>>> I want to offer the dialect of the language D2.0, suitable for use where
>>> are now used C/C++. Main goal of this is making language like D, but
>>> corresponding "zero-overhead principle" like C++:
>>>...
>>> The code on this language almost as dangerous as a code on C++ - it is a
>>> necessary cost for increasing performance.
>> 
>> No, thanks...
>> 
>> And regarding performance, eventually it will come a lot from a good usage of multiprocessing, that in real-world programs may need pure functions and immutable data. That D2 has already, while C++ is less lucky.
>> 
>> Bye,
>> bearophile
> 
> Multiprocessing can only improve performance for tasks that can run
> in parallel.  So far, every attempt to do this with GC (that I know
> of) has ended up slower, not faster.  Bottom line, if GC is the
> bottleneck, more CPU's won't help. 
> 
> For applications where GC performance is unacceptable, we either need
> a radically new way to do GC faster, rely less on the GC, or drop GC
> altogether. 
> 
> However, in D, we can't get rid of the GC altogether, since the
> compiler relies on it.  But we can use explicit memory management
> where it makes sense to do so. 
> 
> -Craig

I think that the "shared" memory concept in D2 is introduced
specifically to improve multi-processing GC performance.  There going to
be thread-local GC for every thread allocating memory, and, since
thread-local will be the default allocation strategy, most memory will
be GCed without synchronizing with other threads.