For numerical algorithms and to get a more low level understanding of the equations, we can expand all terms to the simpler and more explicit form:
How to make a cloud chamber by Suzie Sheehy (2011)
Source. 64 bits is still too much address for current RAM sizes, so most architectures will use less bits.
x86_64 uses 48 bits (256 TiB), and legacy mode's PAE already allows 52-bit addresses (4 PiB). 56-bits is a likely future candidate.
12 of those 48 bits are already reserved for the offset, which leaves 36 bits.
If a 2 level approach is taken, the best split would be two 18 bit levels.
But that would mean that the page directory would have
2^18 = 256K entries, which would take too much RAM: close to a single-level paging for 32 bit architectures!Therefore, 64 bit architectures create even further page levels, commonly 3 or 4.
x86_64 uses 4 levels in a
9 | 9 | 9 | 9 scheme, so that the upper level only takes up only 2^9 higher level entries.The 48 bits are split equally into two disjoint parts:
----------------- FFFFFFFF FFFFFFFF
Top half
----------------- FFFF8000 00000000
Not addressable
----------------- 00007FFF FFFFFFFF
Bottom half
----------------- 00000000 00000000A 5-level scheme is emerging in 2016: software.intel.com/sites/default/files/managed/2b/80/5-level_paging_white_paper.pdf which allows 52-bit addresses with 4k pagetables.
Ciro Santilli feels that Ciro Santilli Myers-Briggs Type Indicator is much more random/hard to determine than the Big Five personality traits
Upon a quick look Ciro Santilli evaluates himself as INTJ.
Physical address extension.
With 32 bits, only 4GB RAM can be addressed.
This started becoming a limitation for large servers, so Intel introduced the PAE mechanism to Pentium Pro.
To relieve the problem, Intel added 4 new address lines, so that 64GB could be addressed.
Page table structure is also altered if PAE is on. The exact way in which it is altered depends on weather PSE is on or off.
PAE is turned on and off via the
PAE bit of cr4.Even if the total addressable memory is 64GB, individual process are still only able to use up to 4GB. The OS can however put different processes on different 4GB chunks.
Let's check relevancy of known hits:Output:
grep -e '208.254.40' -e '208.254.42' 208 | tee 208hits208.254.40.95 1355564700 unreachable
208.254.40.95 1355622300 unreachable
208.254.40.96 1334537100 alive, 36342
208.254.40.96 1335269700 alive, 17586
..
208.254.40.127 1355562900 alive, 35023
208.254.40.127 1355593500 alive, 59866
208.254.40.128 1334609100 unreachable
208.254.40.128 1334708100 alive from 208.254.32.214, 43358
208.254.40.128 1336596300 unreachableThe rest of 208 is mostly unreachable.
208.254.42.191 1335294900 unreachable
...
208.254.42.191 1344737700 unreachable
208.254.42.191 1345574700 Icmp Error: 0,ICMP Network Unreachable, from 63.111.123.26
208.254.42.191 1346166900 unreachable
...
208.254.42.191 1355665500 unreachable
208.254.42.192 1334625300 alive, 6672
...
208.254.42.192 1355658300 alive, 57412
208.254.42.193 1334677500 alive, 28985
208.254.42.193 1336524300 unreachable
208.254.42.193 1344447900 alive, 8934
208.254.42.193 1344613500 alive, 24037
208.254.42.193 1344806100 alive, 20410
208.254.42.193 1345162500 alive, 10177
...
208.254.42.223 1336590900 alive, 23284
...
208.254.42.223 1355555700 alive, 58841
208.254.42.224 1334607300 Icmp Type: 11,ICMP Time Exceeded, from 65.214.56.142
208.254.42.224 1334681100 Icmp Type: 11,ICMP Time Exceeded, from 65.214.56.142
208.254.42.224 1336563900 Icmp Type: 11,ICMP Time Exceeded, from 65.214.56.142
208.254.42.224 1344451500 Icmp Type: 11,ICMP Time Exceeded, from 65.214.56.138
208.254.42.224 1344566700 unreachable
208.254.42.224 1344762900 unreachableLet's try with 66. First there way too much data, 9 GB, let's cut it down:
n=66
time awk '$3~/^alive,/ { print $1 }' $n | uniq -c | sed -r 's/^ +//;s/ /,/' | tee $n-up-uniq-cOK down to 45 MB, now we can work.
grep -e '66.45.179' -e '66.104.169' -e '66.104.173' -e '66.104.175' -e '66.175.106' '66-alive-uniq-c' | tee 66hitsNah, it's full of holes:won't be able to find new ranges here.
4,66.45.179.187
12,66.45.179.188
2,66.45.179.197
1,66.45.179.202
2,66.45.179.205
2,66.45.179.206
1,66.45.179.207Controlled quantum gates are gates that have two types of input qubits:These gates can be understood as doing a certain unitary operation only if the control qubits are enabled or disabled.
- control qubits
- operand qubits (terminology made up by Ciro Santilli just now)
The first example to look at is the CNOT gate.
Generic controlled quantum gate symbol
. Source. The black dot means "control qubit", and "U" means an arbitrary Unitary operation.
When the operand has a conventional symbol, e.g. the Figure "Quantum NOT gate symbol" for the quantum NOT gate to form the CNOT gate, that symbol is used in the operand instead.
2.5.0 manual prebuilt download install on Ubuntu 20.04 just worked. Launch directly from unzip without install. Play with examples under
install/ExamplesTheir docs are a reasonable way to learn Csound: cabbageaudio.com/docs/introduction/
"Quantum interconnect" refers to methods for linking up smaller quantum processors into a larger system.
As of 2024, seemingly few organizations developing quantum hardware had actually integrated multiple chips in interconnects as part of their main current roadmap. But many acknowledged that this would be an essential step towards scalable compuation.
The name "quantum interconnect" is likely partly a throwback to classical computer's "chip interconnect".
Sample usages of the term:
- news.mit.edu/2023/quantum-interconnects-photon-emission-0105
Researchers have demonstrated directional photon emission, the first step toward extensible quantum interconnects
- qpl.ece.ucsb.edu/research/quantum-interconnects
Gerhard Rempe - Quantum Dynamics by Max Planck Institute of Quantum Optics
. Source. No technical details of course, but they do show off their optical tables quite a bit!Ciro Santilli learned this expression from Angry Video Game Nerd.
Poet, scientists and warriors all in one? Conquerors of the useless.
A wise teacher from University of São Paulo once told the class Ciro Santilli attended an anecdote about his life:It turned out that, about 10 years later, Ciro ended up following this advice, unwittingly.
I used to want to learn Mathematics.But it was very hard.So in the end, I became an engineer, and found an engineering solution to the problem, and married a Mathematician instead.
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