Ciro Santilli @cirosantilli 37

LevelDB Updated 2025-07-16

One "LevelDB" database contains multiple file in a directory. Off the bat inferior to SQLite which stores everything in a single file!

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GNOME Display Manager Updated 2025-07-16

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Cool data embedded in the Bitcoin blockchain / Mt. Gox' shutdown Updated 2025-07-16

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Mt. Gox was the first Cryptocurrency exchange in existence, and when it shutdowon in Febrauary 2014 because the website was crap and they got hacked, some people were not happy at all about their missing funds!

tx 0540b5dda23ee870330c6b1e18a88c592cf8d847c47f1dc1d5328f46115b12b3 (2014-02-25)

2014-02-25: The day Mt.Gox shut down. Farewell, may even you rest in peace!

tx 2374f8575f65763caf6909551c131d3ae45399a73aee638bcbccaebdb1219d67 (2014-02-25):

Fuck you MtGox
Fuck you MtGox
R

tx c00a4a04905a2e8d8dee8a768165aa6bdf842413a8a648462a6349db89cd77f2 (2014-02-27) has an ASCII art of a seal, TODO understand meme:

        o
      / |
      | \
  .   |  |
.'\`  | \|
  | \_/ \ \
  \____/\/
<3 You Seals!

There are also a few Base58 messages referring to Mt Gox, the nicest and most expensive one being to burn addres:

1FuckMtGoxFFFFFFFUUUUUUUUUUQXW5ik

which as of 2025 holds 0.014537 BTC burnt on:

14x 0.001 BTC transactions starting at tx b170551d4df68d714fa98189c73f61b0c2bc54cafe33a2953fcc0bc11f6aa72a block 287826 (2014-02-26)
plus one 0.001337 BTC transaction in the middle at tx 6b878716d1d9af0f50de441f318da68121261a5778fd541def4408c0aac531f6 block 287868 (2014-02-26), why not.

Many of these transactions also contain other quick messages, e.g.:

tx e6d4cfbbc45b5e3cfcfa36613b04a8732c7b4606f5dbbd8af3ba06d8f3899fc2 also features a Rickrolling instance.
tx 10a9bb0625447df044410cf9cd74742ec0bf334d48b4b1f93c10a4a60748bb5d also features Nigger inside a spendable vanity address: 1Niggerw15VezU6rA7jRBuJt9ceg9VL1jh

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g4ad.xlarge Updated 2025-07-16

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AMD GPUs as mentioned at: aws.amazon.com/ec2/instance-types/g4/

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F2Pool Updated 2025-07-16

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www.f2pool.com/

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Knowledge graph Updated 2025-07-16

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Many people believe that knowledge graphs are a key element of AGI: Knowledge graph as a component of AGI.

Bibligraphy:

www.knowledgegraph.tech/ The Knowledge graph Conference

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Cool data embedded in the Bitcoin blockchain / Cursed ordinal Updated 2025-07-16

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These were ordinals that were only indexed in later versions of the script. So to prevent changing the useless indices of existing ordinals, they gave them negative numbers.

The word "cursed" is a meme from the 2010/20s, e.g. knowyourmeme.com/memes/cursed-images--2.

Some examples:

ordinals.com/inscription/4b9a822a057743813efbefa0dd21d0a01342ee793ce2ce5bd499a5f262187553i0 first inscription with no mime type.
ordinals.com/inscription/2fa287270e4203ca2fc9f82ea3de7a0f7b785875791a76387ef6f4ccbb54eee2i0 is -38:
Hello World, this is a Rust Taproot test
is bugged because it is missing the mime type, on Python:
```
[b"'a\xf9\x19X%\xa8Q\x87SP\xe5\xf2H\xa6\xeew\x0e\x81\xa5hl\xcd\xaa\x97e\xfeqJ\x16\x12?", OP_CHECKSIG, 0, OP_IF, b'ord', 1, b'text/plain', 0, b'Hello World, this is a Rust Taproot test\xe2\x80\xa6', OP_ENDIF]
```
because the 1 should instead be b'\x01.

Bibliography:

decrypt.co/212908/mysterious-ordinals-inscription-teases-cursed-bitcoin-art-project

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Connect two computers directly without a router with an Ethernet cable Updated 2025-07-16

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For IP-level communication, askubuntu.com/questions/22835/how-to-network-two-ubuntu-computers-using-ethernet-without-a-router/116680#116680 just worked between P51 and P14s both on Ubuntu 23.10 connected with a regular Cat 5e cable.

On both machines, first we found the Ethernet cable interface name with the ip CLI tool:

ip a

which outputs on the P41s:

1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 127.0.0.1/8 scope host lo
       valid_lft forever preferred_lft forever
    inet6 ::1/128 scope host
       valid_lft forever preferred_lft forever
2: enp1s0f0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP group default qlen 1000
    link/ether fc:5c:ee:24:fb:b4 brd ff:ff:ff:ff:ff:ff
3: wlp2s0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP group default qlen 1000
    link/ether 04:7b:cb:cc:1b:10 brd ff:ff:ff:ff:ff:ff
    inet 192.168.1.123/24 brd 192.168.1.255 scope global dynamic noprefixroute wlp2s0
       valid_lft 61284sec preferred_lft 61284sec
    inet6 fe80::3597:15d8:74ff:e112/64 scope link noprefixroute
       valid_lft forever preferred_lft forever

so the interface was enp1s0f0, because wlp is wireless and lo is localhost.

So on the P14s we assign an IP of 10.0.0.10 to the P51:

sudo ip address add 10.0.0.10/24 dev enp1s0f0

Then on the P51 analogously, giving IP of 10.0.0.20 to the P14s:

sudo ip address add 10.0.0.20/24 dev enp0s31f6

And after that, P14s can:

ping 10.0.0.10

and P51 can:

ping 10.0.0.20

TODO after a few seconds, the settings appear to be forgotten, and ping stops working unless you do sudo ip address add on the local machine again. This seems to happen after a popup appears saying "Activation of network connection failed" as it fails to obtain Internet from the cable.

TODO list and delete such manual assignments we've made.

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Computer science course of the University of Cambridge Updated 2025-07-16

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The courses are highly open, almost everything is given publicly except solutions, many of which are given to teachers only. Well done!

Past exam papers index: www.cl.cam.ac.uk/teaching/exams/pastpapers/

www.cl.cam.ac.uk/teaching/2223/