d future or plans for d3

[Robert Jacques]

On Sun, 18 Dec 2011 15:28:16 -0800, Andrei Alexandrescu <SeeWebsiteForEmail at erdani.org> wrote:

> On 12/18/11 5:22 PM, Vladimir Panteleev wrote:
>> On Sunday, 18 December 2011 at 23:13:03 UTC, Andrei Alexandrescu wrote:
>>> On 12/18/11 4:53 PM, Vladimir Panteleev wrote:
>>>> On Sunday, 18 December 2011 at 20:32:18 UTC, Andrei Alexandrescu wrote:
>>>>> That is an interesting opportunity. At any rate, I am 100% convinced
>>>>> precise GC is the only way to go, and I think I've convinced Walter to
>>>>> a good extent as well.
>>>>
>>>> Sacrificing something (performance, executable size) for something else
>>>> is not an unilateral improvement.
>>>
>>> I think we can do a lot toward improving the footprint and performance
>>> of a precise GC while benefitting of its innate advantages.
>>
>> Still, a more conservative GC will always outperform a more precise one
>> in scanning speed.
>
> I'm not sure. I seem to recall discussions with pathological cases when
> large regions of memory were scanned for no good reason.
>

Scanning speed is proportional to the size of the live heap, which will always be larger for conservative collectors. So while conservative collectors are faster per byte, they have to scan more bytes. There's been a bunch of research into precise GCs for C, as graduate students love hard problems. There are several solutions out there currently; the one I stumbled upon is called Magpie. The associated thesis has some pretty in depth performance analyses. There are also some follow up papers from later students and more real world tests of precise vs conservative vs manual.