On Mon, Sep 7, 2009 at 6:33 PM, Edouard A. <edouard@fausse.info> wrote:
I was wondering if it would be interesting to provide some generic template classes making >easier this kind of optimization.
Yes, at least for me.
You actually have more than one bit available as the OS generally reserves a huge area of virtual memory for the kernel. Typical example, Windows 32, maximum user pointer value is 0x80000000. Don't remember the values by heart for the other oses.
This is incorrect. The pointer limit is only limited to under 0x80000000 if you are linking without the /LARGEADDRESSAWARE flag. It is quite common to use this flag to enable the best performance of a 32-bit application on a 64-bit version of Windows. It can also have some benefit when using the boot.ini /3GB tuning. http://msdn.microsoft.com/en-us/library/wz223b1z%28VS.80%29.aspx
On 64-bit OSes you really can use the large pointers to store data and therefore have very compact structures in memory. Correct me if I'm wrong but currently most OSes only allow several gigabytes of virtual memory for any given user process (something like 100-200 GB), that means there's room for expression! :D
The limit is as high as 8TB on some Windows 64-bit Operating Systems. http://msdn.microsoft.com/en-us/library/aa366778%28VS.85%29.aspx
In addition, embedding a tag within a pointer is a technique to reduce the ABA problem occurrence on lockfree containers.
It would be a nice to have IMHO, but there is a huge work of testing to make it safe and reliable.
Agreed.
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EA
Regards, Neil Groves