Ciro Santilli @cirosantilli 37

Ciro Santilli 37  Updated 2025-05-21  +Created 1970-01-01

Forest: an Operating System for Quantum Computing by Guen Prawiroatmodjo (2017)

Source. The title of the talk is innapropriate, this is a very basic overview of the entire Rigetti Computing stack. Still some fine mentions. Her name is so long, TODO origin? She later moved to Microsoft Quantum: www.linkedin.com/in/gueneverep/.

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Pasqal by

Ciro Santilli 37  Updated 2025-05-21  +Created 1970-01-01

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pasqal.io/

Funding:

2023: $100m techcrunch.com/2023/01/23/pasqal-raises-100m-to-build-a-neutral-atom-based-quantum-computer/

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FeathersJS by

Ciro Santilli 37  Updated 2025-05-21  +Created 1970-01-01

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Looks interesting.

It seems to abstract the part about the client messaging the backend, which focuses on being able to easily plug in a number of Front-end web framework to manage client state.

Has the "main web API is the same as the REST API" focus, which is fundamental 2020-nowadays.

Uses Socket.IO, which allows the client Javascript to register callbacks when data is updated to achieve Socket.IO, e.g. their default chat app does:

client.service('messages').on('created', addMessage);

so that message appear immediately as they are sent.

Their standard template from feathers generate app on @feathersjs/cli@4.5.0 includes:

several authentication methods, including OAuth
testing
backend database with one of several object-relational mapping! However, they don't abstract across them. E.g., the default Chat example uses NeDB, but a real app will likely use Sequelize, and a port is needed

which looks promising! They don't have a default template for a Front-end web framework however unfortunately: docs.feathersjs.com/guides/frameworks.html#the-feathers-chat lists a few chat app versions, which is their hello world:

Front-end web framework: not built-in on generator, but there are some sample repos pointed from the documentation, and they did work out-of-box:
- feathers-chat-react

But it is in itself a completely boring app with a single splash page, and no database interaction, so not a good showcase. The actual showcase app is feathersjs/feathers-chat.

And there is no official example of the chat app that is immediately deployable to Heroku: FeathersJS Heroku deployment, all setups require thinking.

Global source entry point: determine on package.json as usual, defaults to src/index.js.

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Node.js database bindings by

Ciro Santilli 37  Updated 2025-05-21  +Created 1970-01-01

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node.js SQLite bindings

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Money creation vs tax by

Ciro Santilli 37  Updated 2025-05-21  +Created 1970-01-01

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politics.stackexchange.com/questions/73498/how-is-printing-money-different-from-taxing-people

To Ciro Santilli, a key observation is:

The rich are more easily able to avoid the harm than poor and middle-class people [...] they are more likely to have large amounts of non-cash assets to shield themselves from inflation.

Clearly the rich will be much, much more shielded by keeping large parts of their wealth in shares... from this point of view, it is insane to print money!!! Tax the rich instead...

Mentions:

Erik Finman: twitter.com/erikfinman/status/1446853065320112130

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Dan Jewett by

Ciro Santilli 37  Updated 2025-05-21  +Created 1970-01-01

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MacKenzie Bezos' new husband after she divorced Bezos.

Science teacher at the Lakeside School in Seattle.

www.dailymail.co.uk/femail/article-9338723/Who-billionaire-Mackenzie-Scotts-new-husband-Dan-Jewett.html Who IS billionaire Mackenzie Scott's new husband Dan Jewett?

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Lattice Microbes by

Ciro Santilli 37  Updated 2025-05-21  +Created 1970-01-01

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GPU accelerated, simulates the Craig's minimized M. genitalium, JCVI-syn3A at a particle basis of some kind.

Lab head is the cutest-looking lady ever: chemistry.illinois.edu/zan, Zaida (Zan) Luthey-Schulten.

2022 paper: www.cell.com/cell/fulltext/S0092-8674(21)01488-4 Fundamental behaviors emerge from simulations of a living minimal cell by Thornburg et al. (2022) published on Cell
faculty.scs.illinois.edu/schulten/lm/ actual source code. No Version control and non-code drop release, openess and best practices haven't reached such far obscure reaches of academia yet. One day.
blogs.nvidia.com/blog/2022/01/20/living-cell-simulation/ Nvidia announcement. That's how they do business, it is quite interesting how they highlight this kind of research.
- catalog.ngc.nvidia.com/orgs/hpc/containers/lattice-microbes has a container

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Larry Page by

Ciro Santilli 37  Updated 2025-05-21  +Created 1970-01-01

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Mitochondrial DNA mutates faster than nuclear DNA by

Ciro Santilli 37  Updated 2025-05-21  +Created 1970-01-01

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Wikipedia mentions "Since animal mtDNA evolves faster than nuclear genetic markers" with a few sources.

Some sources:

Power, Sex, Suicide by Nick Lane (2006) page 361 mentions:
While nuclear DNA can barely distinguish between chimps and humans, the mitochondrial clock ticks fast enough to reveal differences accumulating over tens of thousands of years
so this property is also important for the human mitochondrial molecular clock.
www.ncbi.nlm.nih.gov/pmc/articles/PMC3350313 says it for metazoans
www.quora.com/Why-does-mitochondrial-DNA-mutate-faster

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Intel Xe by

Ciro Santilli 37  Updated 2025-05-21  +Created 1970-01-01

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Hartree-Fock method for the helium atom by

Ciro Santilli 37  Updated 2025-05-21  +Created 1970-01-01

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gothinkster/realworld implementation by

Ciro Santilli 37  Updated 2025-05-21  +Created 1970-01-01

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Setups we've tried:

backend:
- randyscotsmithey/feathers-realworld-example-app worked with React and Vue.js
- the React setup failed as shown at: github.com/gothinkster/react-redux-realworld-example-app/issues/187
- gothinkster/django-realworld-example-app
- the Nest.js failed on Ubuntu 20.10 as per github.com/lujakob/nestjs-realworld-example-app/issues/19
frontend:

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GitLab cookbook by

Ciro Santilli 37  Updated 2025-05-21  +Created 1970-01-01

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gitlab.com/gitlab-org/cookbook-gitlab

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Pull request by

Ciro Santilli 37  Updated 2025-05-21  +Created 1970-01-01

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The heart/main innovation of GitHub!

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Eukaryotic small ribosome subunit by

Ciro Santilli 37  Updated 2025-05-21  +Created 1970-01-01

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University of Cambridge spinout company by

Ciro Santilli 37  Updated 2025-05-21  +Created 1970-01-01

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ELF Hello World Tutorial / .data section by

Ciro Santilli 37  Updated 2025-05-21  +Created 1970-01-01

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.data is section 1:

00000080  01 00 00 00 01 00 00 00  03 00 00 00 00 00 00 00  |................|
00000090  00 00 00 00 00 00 00 00  00 02 00 00 00 00 00 00  |................|
000000a0  0d 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
000000b0  04 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|

80 0: sh_name = 01 00 00 00: index 1 in the .shstrtab string table
Here, 1 says the name of this section starts at the first character of that section, and ends at the first NUL character, making up the string .data.
.data is one of the section names which has a predefined meaning according to www.sco.com/developers/gabi/2003-12-17/ch4.strtab.html:
These sections hold initialized data that contribute to the program's memory image.

80 4: sh_type = 01 00 00 00: SHT_PROGBITS: the section content is not specified by ELF, only by how the program interprets it. Normal since a .data section.
80 8: sh_flags = 03 7x 00: SHF_WRITE and SHF_ALLOC: www.sco.com/developers/gabi/2003-12-17/ch4.sheader.html#sh_flags, as required from a .data section
90 0: sh_addr = 8x 00: TODO: standard says:
If the section will appear in the memory image of a process, this member gives the address at which the section's first byte should reside. Otherwise, the member contains 0.
but I don't understand it very well yet.
90 8: sh_offset = 00 02 00 00 00 00 00 00 = 0x200: number of bytes from the start of the program to the first byte in this section
a0 0: sh_size = 0d 00 00 00 00 00 00 00
If we take 0xD bytes starting at sh_offset 200, we see:
```
00000200  48 65 6c 6c 6f 20 77 6f  72 6c 64 21 0a 00        |Hello world!..  |
```
AHA! So our "Hello world!" string is in the data section like we told it to be on the NASM.
Once we graduate from hd, we will look this up like:
```
readelf -x .data hello_world.o
```
which outputs:
```
Hex dump of section '.data':
  0x00000000 48656c6c 6f20776f 726c6421 0a       Hello world!.
```
NASM sets decent properties for that section because it treats .data magically: www.nasm.us/doc/nasmdoc7.html#section-7.9.2
Also note that this was a bad section choice: a good C compiler would put the string in .rodata instead, because it is read-only and it would allow for further OS optimizations.
- a0 8: sh_link and sh_info = 8x 0: do not apply to this section type. www.sco.com/developers/gabi/2003-12-17/ch4.sheader.html#special_sections
- b0 0: sh_addralign = 04 = TODO: why is this alignment necessary? Is it only for sh_addr, or also for symbols inside sh_addr?
- b0 8: sh_entsize = 00 = the section does not contain a table. If != 0, it means that the section contains a table of fixed size entries. In this file, we see from the readelf output that this is the case for the .symtab and .rela.text sections.

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ELF Hello World Tutorial / .symtab by

Ciro Santilli 37  Updated 2025-05-21  +Created 1970-01-01

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Section type: sh_type == SHT_SYMTAB.

Common name: "symbol table".

First the we note that:

sh_link = 5
sh_info = 6

For SHT_SYMTAB sections, those numbers mean that:

strings that give symbol names are in section 5, .strtab
the relocation data is in section 6, .rela.text

A good high level tool to disassemble that section is:

nm hello_world.o

which gives:

0000000000000000 T _start
0000000000000000 d hello_world
000000000000000d a hello_world_len

This is however a high level view that omits some types of symbols and in which the symbol types . A more detailed disassembly can be obtained with:

readelf -s hello_world.o

which gives:

Symbol table '.symtab' contains 7 entries:
   Num:    Value          Size Type    Bind   Vis      Ndx Name
     0: 0000000000000000     0 NOTYPE  LOCAL  DEFAULT  UND
     1: 0000000000000000     0 FILE    LOCAL  DEFAULT  ABS hello_world.asm
     2: 0000000000000000     0 SECTION LOCAL  DEFAULT    1
     3: 0000000000000000     0 SECTION LOCAL  DEFAULT    2
     4: 0000000000000000     0 NOTYPE  LOCAL  DEFAULT    1 hello_world
     5: 000000000000000d     0 NOTYPE  LOCAL  DEFAULT  ABS hello_world_len
     6: 0000000000000000     0 NOTYPE  GLOBAL DEFAULT    2 _start

The binary format of the table is documented at www.sco.com/developers/gabi/2003-12-17/ch4.symtab.html

The data is:

readelf -x .symtab hello_world.o

which gives:

Hex dump of section '.symtab':
  0x00000000 00000000 00000000 00000000 00000000 ................
  0x00000010 00000000 00000000 01000000 0400f1ff ................
  0x00000020 00000000 00000000 00000000 00000000 ................
  0x00000030 00000000 03000100 00000000 00000000 ................
  0x00000040 00000000 00000000 00000000 03000200 ................
  0x00000050 00000000 00000000 00000000 00000000 ................
  0x00000060 11000000 00000100 00000000 00000000 ................
  0x00000070 00000000 00000000 1d000000 0000f1ff ................
  0x00000080 0d000000 00000000 00000000 00000000 ................
  0x00000090 2d000000 10000200 00000000 00000000 -...............
  0x000000a0 00000000 00000000                   ........

The entries are of type:

typedef struct {
    Elf64_Word  st_name;
    unsigned char   st_info;
    unsigned char   st_other;
    Elf64_Half  st_shndx;
    Elf64_Addr  st_value;
    Elf64_Xword st_size;
} Elf64_Sym;

Like in the section table, the first entry is magical and set to a fixed meaningless values.

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ELF Hello World Tutorial / Specified file formats by

Ciro Santilli 37  Updated 2025-05-21  +Created 1970-01-01

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The ELF standard specifies multiple file formats:

Object files (.o).
Intermediate step to generating executables and other formats:
```
Source code

    |
    | Compilation
    |
    v

Object file

    |
    | Linking
    |
    v

Executable
```
Object files exist to make compilation faster: with make, we only have to recompile the modified source files based on timestamps.
We have to do the linking step every time, but it is much less expensive.

Executable files (no standard Linux extension).
This is what the Linux kernel can actually run.

Archive files (.a).
Libraries meant to be embedded into executables during the Linking step.

Shared object files (.so).
Libraries meant to be loaded when the executable starts running.

Core dumps.
Such files may be generated by the Linux kernel when the program does naughty things, e.g. segfault.
They exist to help debugging the program.

In this tutorial, we consider only object and executable files.

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Diffraction of Cathode Rays by a Thin Film by Thomson and Reid (1927) by

Ciro Santilli 37  Updated 2025-05-21  +Created 1970-01-01

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www.nature.com/articles/119890a0

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