From: Sam Schetterer (samthecppman_at_[hidden])
Date: 2007-03-31 18:34:39
On 3/31/07, Richard Day <richardvday_at_[hidden]> wrote:
> Basically I would gather from this that a 10gb file for example would
> take 30gb of disk space to sort it ?
> That would appear to be what your suggesting here.
> And why 1/16 specifically ? Wouldnt it be better to use available memory
> (Free real not paged) if possible instead of specifically doing 1/16'th ?
> 10gb is more then most(Non-Server) machines have now that is true but
> 2-4gb is becoming more and more common now and of course servers may
> have way more then 10gb.
>
> Seems to me that if your going to do this much writing(2 X Original
> size) wouldnt it be simpler to just use a memory mapped file.
No, it is not 2x prignal size on disk. This illustration should help
o o o o o o o o o o
o o o o o o o o o o o o o o o o
o o o o o o o o o o o o o
o o o o o o o o o o o o o
beomes (I leave out much data for simplicity)
o o o o o
o o o o o
o o o o o
o o o o o
o o o o o
which becomes
ooooo
ooooo
ooooo
ooooo
ooooo
all on one big file in memory. That is what I am trying to say.