Ciro Santilli @cirosantilli 35

 Top articles  New articles  Updated articles  New discussions  Top discussions  New comments  Follows  Followed by  Liked articles  Followed articles  Liked discussions  Followed discussions  Received likes

Section header table  Updated 2025-01-10  +Created 1970-01-01

 View more

Array of Elf64_Shdr structs.

Each entry contains metadata about a given section.

e_shoff of the ELF header gives the starting position, 0x40 here.

e_shentsize and e_shnum from the ELF header say that we have 7 entries, each 0x40 bytes long.

So the table takes bytes from 0x40 to 0x40 + 7 + 0x40 - 1 = 0x1FF.

Some section names are reserved for certain section types: www.sco.com/developers/gabi/2003-12-17/ch4.sheader.html#special_sections e.g. .text requires a SHT_PROGBITS type and SHF_ALLOC + SHF_EXECINSTR

Running:

readelf -S hello_world.o

outputs:

There are 7 section headers, starting at offset 0x40:

Section Headers:
  [Nr] Name              Type             Address           Offset
       Size              EntSize          Flags  Link  Info  Align
  [ 0]                   NULL             0000000000000000  00000000
       0000000000000000  0000000000000000           0     0     0
  [ 1] .data             PROGBITS         0000000000000000  00000200
       000000000000000d  0000000000000000  WA       0     0     4
  [ 2] .text             PROGBITS         0000000000000000  00000210
       0000000000000027  0000000000000000  AX       0     0     16
  [ 3] .shstrtab         STRTAB           0000000000000000  00000240
       0000000000000032  0000000000000000           0     0     1
  [ 4] .symtab           SYMTAB           0000000000000000  00000280
       00000000000000a8  0000000000000018           5     6     4
  [ 5] .strtab           STRTAB           0000000000000000  00000330
       0000000000000034  0000000000000000           0     0     1
  [ 6] .rela.text        RELA             0000000000000000  00000370
       0000000000000018  0000000000000018           4     2     4
Key to Flags:
  W (write), A (alloc), X (execute), M (merge), S (strings), l (large)
  I (info), L (link order), G (group), T (TLS), E (exclude), x (unknown)
  O (extra OS processing required) o (OS specific), p (processor specific)

The struct represented by each entry is:

typedef struct {
    Elf64_Word  sh_name;
    Elf64_Word  sh_type;
    Elf64_Xword sh_flags;
    Elf64_Addr  sh_addr;
    Elf64_Off   sh_offset;
    Elf64_Xword sh_size;
    Elf64_Word  sh_link;
    Elf64_Word  sh_info;
    Elf64_Xword sh_addralign;
    Elf64_Xword sh_entsize;
} Elf64_Shdr;

 Read the full article

Personal name  Updated 2025-01-10  +Created 1970-01-01

 Read the full article

The Godfather  Updated 2025-01-10  +Created 1970-01-01

 View more

www.youtube.com/playlist?list=PLVV0r6CmEsFzCodipONmNiROhYCUWyz_U interview with Walter Murch by Web of Stories. He worked on sound design for all The Godfather films, and tells some interesting details about it. He's just super nice in general otherwise. E.g.:

www.youtube.com/watch?v=w4OK8__gfGo talks about the sound design for the restaurant scene in The Godfather Part II (1974)

Video 1.

Francis Coppola's Notebook on The Godfather

. Source.

 Read the full article

Symmetric and public-key cryptography  Updated 2025-01-10  +Created 1970-01-01

 Read the full article

Digital electronic circuit  Updated 2025-01-10  +Created 1970-01-01

 Read the full article

Gene  Updated 2025-01-10  +Created 1970-01-01

 Read the full article

Object hd  Updated 2025-01-10  +Created 1970-01-01

 View more

Running:

hd hello_world.o

gives:

00000000  7f 45 4c 46 02 01 01 00  00 00 00 00 00 00 00 00  |.ELF............|
00000010  01 00 3e 00 01 00 00 00  00 00 00 00 00 00 00 00  |..>.............|
00000020  00 00 00 00 00 00 00 00  40 00 00 00 00 00 00 00  |........@.......|
00000030  00 00 00 00 40 00 00 00  00 00 40 00 07 00 03 00  |....@.....@.....|
00000040  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
*
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  |................|
000000c0  07 00 00 00 01 00 00 00  06 00 00 00 00 00 00 00  |................|
000000d0  00 00 00 00 00 00 00 00  10 02 00 00 00 00 00 00  |................|
000000e0  27 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |'...............|
000000f0  10 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
00000100  0d 00 00 00 03 00 00 00  00 00 00 00 00 00 00 00  |................|
00000110  00 00 00 00 00 00 00 00  40 02 00 00 00 00 00 00  |........@.......|
00000120  32 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |2...............|
00000130  01 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
00000140  17 00 00 00 02 00 00 00  00 00 00 00 00 00 00 00  |................|
00000150  00 00 00 00 00 00 00 00  80 02 00 00 00 00 00 00  |................|
00000160  a8 00 00 00 00 00 00 00  05 00 00 00 06 00 00 00  |................|
00000170  04 00 00 00 00 00 00 00  18 00 00 00 00 00 00 00  |................|
00000180  1f 00 00 00 03 00 00 00  00 00 00 00 00 00 00 00  |................|
00000190  00 00 00 00 00 00 00 00  30 03 00 00 00 00 00 00  |........0.......|
000001a0  34 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |4...............|
000001b0  01 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
000001c0  27 00 00 00 04 00 00 00  00 00 00 00 00 00 00 00  |'...............|
000001d0  00 00 00 00 00 00 00 00  70 03 00 00 00 00 00 00  |........p.......|
000001e0  18 00 00 00 00 00 00 00  04 00 00 00 02 00 00 00  |................|
000001f0  04 00 00 00 00 00 00 00  18 00 00 00 00 00 00 00  |................|
00000200  48 65 6c 6c 6f 20 77 6f  72 6c 64 21 0a 00 00 00  |Hello world!....|
00000210  b8 01 00 00 00 bf 01 00  00 00 48 be 00 00 00 00  |..........H.....|
00000220  00 00 00 00 ba 0d 00 00  00 0f 05 b8 3c 00 00 00  |............<...|
00000230  bf 00 00 00 00 0f 05 00  00 00 00 00 00 00 00 00  |................|
00000240  00 2e 64 61 74 61 00 2e  74 65 78 74 00 2e 73 68  |..data..text..sh|
00000250  73 74 72 74 61 62 00 2e  73 79 6d 74 61 62 00 2e  |strtab..symtab..|
00000260  73 74 72 74 61 62 00 2e  72 65 6c 61 2e 74 65 78  |strtab..rela.tex|
00000270  74 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |t...............|
00000280  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
00000290  00 00 00 00 00 00 00 00  01 00 00 00 04 00 f1 ff  |................|
000002a0  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
000002b0  00 00 00 00 03 00 01 00  00 00 00 00 00 00 00 00  |................|
000002c0  00 00 00 00 00 00 00 00  00 00 00 00 03 00 02 00  |................|
000002d0  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
000002e0  11 00 00 00 00 00 01 00  00 00 00 00 00 00 00 00  |................|
000002f0  00 00 00 00 00 00 00 00  1d 00 00 00 00 00 f1 ff  |................|
00000300  0d 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
00000310  2d 00 00 00 10 00 02 00  00 00 00 00 00 00 00 00  |-...............|
00000320  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
00000330  00 68 65 6c 6c 6f 5f 77  6f 72 6c 64 2e 61 73 6d  |.hello_world.asm|
00000340  00 68 65 6c 6c 6f 5f 77  6f 72 6c 64 00 68 65 6c  |.hello_world.hel|
00000350  6c 6f 5f 77 6f 72 6c 64  5f 6c 65 6e 00 5f 73 74  |lo_world_len._st|
00000360  61 72 74 00 00 00 00 00  00 00 00 00 00 00 00 00  |art.............|
00000370  0c 00 00 00 00 00 00 00  01 00 00 00 02 00 00 00  |................|
00000380  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
00000390

 Read the full article

gvgai  Updated 2025-01-10  +Created 1970-01-01

 View more

www.gvgai.net (dead as of 2023)

The project kind of died circa 2020 it seems, a shame. Likely they funding ran out. The domain is dead as of 2023, last archive from 2022: web.archive.org/web/20220331022932/http://gvgai.net/. Marks as funded by DeepMind. Researchers really should use university/GitHub domain names!

Similar goals to Ciro's 2D reinforcement learning games, but they were focusing mostly on discrete games.

They have some source at: github.com/GAIGResearch/GVGAI TODO review

A published book at: gaigresearch.github.io/gvgaibook/

From QMUL Game AI Research Group:

Simon M. Lucas: gaigresearch.github.io/members/Simon-Lucas, principal investigator
Diego Perez Liebana www.linkedin.com/in/diegoperezliebana/
Raluca D. Gaina: www.linkedin.com/in/raluca-gaina-347518114/ from Queen Mary

From other universities:

Julian Togelius

TODO check:

Ahmed Khalifa
Jialin Liu

 Read the full article

Propositional logic  Updated 2025-01-10  +Created 1970-01-01

 View more

This is the part of the formalization of mathematics that deals only with the propositions.

In some systems, e.g. including Metamath, modus ponens alone tends to be enough, everything else can be defined based on it.

 Read the full article

Unified Modeling Language  Updated 2025-01-10  +Created 1970-01-01

 Read the full article

5v vs 3.3V  Updated 2025-01-10  +Created 1970-01-01

 View more

 Read the full article

AC adapter  Updated 2025-01-10  +Created 1970-01-01

 View more

 Read the full article

De novo DNA synthesis  Updated 2025-01-10  +Created 1970-01-01

 View more

As of 2018, Ciro Santilli believes that this could be the next big thing in biology technology.

"De novo" means "starting from scratch", that is: you type the desired sequence into a computer, and the synthesize it.

The "de novo" part is important, because it distinguishes this from the already well solved problem of duplicating DNA from an existing DNA template, which is what all our cells do daily, and which can already be done very efficiently in vitro with polymerase chain reaction.

Many startup companies are attempting to create more efficient de novo synthesis methods:

Notably, the dream of most of those companies is to have a machine that sits on a lab bench, which synthesises whatever you want.

TODO current de novo synthesis costs/time to delivery after ordering a custom sequence.

The initial main applications are likely going to be:

polymerase chain reaction primers (determine which region will be amplified
creating a custom sequence to be inserted in a plasmid, i.e. artificial gene synthesis

but the real pipe dream is building and bootstraping entire artificial chromosomes

News coverage:

2023-03 twitter.com/sethbannon/status/1633848116154880001
AnsaBio created the world's longest DNA oligo produced using de novo synthesis! 1,005 bases! 99.9% stepwise yield
2020-10-05 www.nature.com/articles/s41587-020-0695-9 "Enzymatic DNA synthesis enters new phase"

Video 1.

Nuclera eDNA enzymatic de novo DNA synthesis explanatory animation (2021)

Source. The video shows nicely how Nuclera's enzymatic DNA synthesis works:

they provide blocked nucleotides of a single type
add them with the enzyme. They use a werid DNA polymerase called terminal deoxynucleotidyl transferase that adds a base at a time to a single stranded DNA strand rather than copying from a template
wash everything
do deblocking reaction
and then repeat until done

 Read the full article

PDF  Updated 2025-01-10  +Created 1970-01-01

 Read the full article

Meh  Updated 2025-01-10  +Created 1970-01-01

 Read the full article

Database management system  Updated 2025-01-10  +Created 1970-01-01

 View more

A software that implements some database system, e.g. PostgreSQL or MySQL are two (widely extended) SQL implementations.

 Read the full article

Directed graph  Updated 2025-01-10  +Created 1970-01-01

 Read the full article

Characteristic polynomial  Updated 2025-01-10  +Created 1970-01-01

 Read the full article

Eigenvector  Updated 2025-01-10  +Created 1970-01-01

 View more

See: eigenvalues and eigenvectors.

 Read the full article

Personal finance  Updated 2025-01-10  +Created 1970-01-01

 View more

the American stock market gives 10% / year, which is about 2x over 10 years. It has been the sure-fire best investment on a 10 year horizon for many decades, and should serve as your benchmark.
risky diversified investments (e.g. ETFs that track a market index) are basically the best investment if you can keep your money in them in the long term (10 years)
risky investments can gown down for a while, and you cannot take your money out then. This effectively means risk is a form of illiquidity
investment funds have taxes, which eat into your profit. The best investments are dumb index tracking investments (like an ETF that tracks the stock market) that are simply brainless to manage, and therefore have lowest taxes. No fund has managed to beat the market long term essentially.
when you are young, ideally you should invest everything into riskier higher yielding assets like stock. And as you get older, you should move part of it to less risky (and therefore more liquid, but lower yielding) assets like bonds
The desire to buy a house however complicates this for many people.

 Read the full article

 Unlisted articles are being shown, click here to show only listed articles.