Re: int128_t
Re: int128_t
- Subject: Re: int128_t
- From: "A.M." <email@hidden>
- Date: Fri, 17 Oct 2008 13:39:36 -0400
On Oct 17, 2008, at 12:34 PM, Rick Mann wrote:
On Oct 17, 2008, at 07:42:10, Sherm Pendley wrote:
The availability of 128-bit chips will not magically expand the
world economy by thousands of orders of magnitude. Using 128-bit
ints at that point will be a matter of convenience, not of necessity.
Not exactly analogous, but: The following observation was made about
ZFS (which uses 128-bit ints for everything) (http://en.wikipedia.org/wiki/ZFS#Capacity
):
Project leader Bonwick said, "Populating 128-bit file systems would
exceed the quantum limits of earth-based storage. You couldn't fill
a 128-bit storage pool without boiling the oceans."[2] Later he
clarified:
Although we'd all like Moore's Law to continue forever, quantum
mechanics imposes some fundamental limits on the computation rate
and information capacity of any physical device. In particular, it
has been shown that 1 kilogram of matter confined to 1 litre of
space can perform at most 1051 operations per second on at most
1031 bits of information.[10] A fully populated 128-bit storage
pool would contain 2128 blocks = 2137 bytes = 2140 bits; therefore
the minimum mass required to hold the bits would be (2140 bits) /
(1031 bits/kg) = 136 billion kg. To operate at the 1031 bits/kg
limit, however, the entire mass of the computer must be in the form
of pure energy. By E=mc², the rest energy of 136 billion kg is
1.2x1028 J. The mass of the oceans is about 1.4x1021 kg. It takes
about 4,000 J to raise the temperature of 1 kg of water by 1 degree
Celsius, and thus about 400,000 J to heat 1 kg of water from
freezing to boiling. The latent heat of vaporization adds another 2
million J/kg. Thus the energy required to boil the oceans is about
2.4x106 J/kg * 1.4x1021 kg = 3.4x1027 J. Thus, fully populating a
128-bit storage pool would, literally, require more energy than
boiling the oceans.[11]
This assumes that every addressable bit is populated and stuffed with
meaningful data which a filesystem most certainly does not do. For
example, how could one address all the bytes of ZFS filesystems across
the nodes in the IPv6 address space? Oops, now you need 256-bit
addressing.
From the "640-KB-ought-to-be-enough-for-anybody" department,
M _______________________________________________
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