Ciro Santilli @cirosantilli 40

 Articles (13k) Discussions (29) Comments (66) Follows  Received likes Files

New Updated  Top  Announced  A-Z  Liked  Followed

D. Richard Hipp Updated 2025-07-16

https://upload.wikimedia.org/wikipedia/en/e/e7/Richard_hipp.jpeg

His standard C header seems to be as per example: www.sqlite.org/src/file/ext/misc/rot13.c

** The author disclaims copyright to this source code.  In place of
** a legal notice, here is a blessing:
**
**    May you do good and not evil.
**    May you find forgiveness for yourself and forgive others.
**    May you share freely, never taking more than you give.

 Read the full article

Drosophila connectome Updated 2025-07-16

 View more

2023 full connectome published on Science by Marta Zlatic's lab at the MRC:

The hard part then is how to make any predictions from it:

2024 www.nature.com/articles/d41586-024-02935-z Fly-brain connectome helps to make predictions about neural activity. Summary of "Connectome-constrained networks predict neural activity across the fly visual system" by J. K. Lappalainen et. al.

2024: www.nature.com/articles/d41586-024-03190-y Largest brain map ever reveals fruit fly's neurons in exquisite detail

As of 2022, it had been almost fully decoded by post mortem connectome extraction with microtome!!! 135k neurons.

2021 www.nytimes.com/2021/10/26/science/drosophila-fly-brain-connectome.html Why Scientists Have Spent Years Mapping This Creature’s Brain by New York Times

That article mentions the humongous paper elifesciences.org/articles/66039 elifesciences.org/articles/66039 "A connectome of the Drosophila central complex reveals network motifs suitable for flexible navigation and context-dependent action selection" by a group from Janelia Research Campus. THe paper is so large that it makes eLife hang.

 Read the full article

Dr. Strangelove Updated 2025-07-16

 View more

Video 1.

Inside the Making of 'Dr. Strangelove' part 2

. Source.

 Read the full article

EC2 instance store volume Updated 2025-07-16

 View more

Large but ephemeral storage for EC2 instances. Predetermined by the EC2 instance type. Stays in the local server disk. Not automatically mounted.

docs.aws.amazon.com/AWSEC2/latest/UserGuide/InstanceStorage.html (archive) notably highlights what it persists, which is basically nothing
serverfault.com/questions/433703/how-to-use-instance-store-volumes-storage-in-amazon-ec2 mentions that you have to mount it

 Read the full article

ecash Updated 2025-07-16

 Read the full article

Eclipse (IDE) Updated 2025-07-16

 View more

Once upon a time (early 2010's), Eclipse dominated the IDE landscape and all was good. NetBeans was around too. And Java was still unmarred by Google LLC v. Oracle America, Inc..

But then something happened.

For some reason, Eclipse started to decay.

And the project that had once been a vibrant community of awesomeness, started to become... a zombie of its former self.

Buggyness started increasing. And not even hard to fix bugs. One liners that affect every user immediately after startup.

Sometimes, to Eclipse's defense they weren't "bugs". Just features that it became evident with time every programmer expected from a modern IDE.

But somehow the Eclipse community had a deep problem. A cancer. It had completely lost touch with user experience.

Perhaps is was due to the increasing interest of the several corporations that had adopted Eclipse as the base IDE for the proprietary solutions?

Perhaps.

Many users stuck to the IDE.

Some heroic efforts were made as plugins that drastically improved certain defects. The Darkest Dark plugin comes to mind.

But all those efforts required configuration. A setup time that most users simply don't have. The core devteam had become dumb and dead, unable to incorporate such changes.

This greatly opened up the space for other competing IDEs to come along. The "semi feature complete but at least easy to use and not so buggy" Visual Studio Code and the proprietary JetBrains IDEs being some of the most notable ones.

Using Eclipse as of the early 2020's is such a mixed experience. If you spend enough time to configure out the key buggyness, there are moments where you can feel "OMG, this feature is amazing".

But the effort is just too great, and soon another bug or obvious missing feature hits you and brings you back to reality.

Every young person uses VS Code now. Eclipse is dead, and there is no way back, usage will just continue dropping.

RIP, Eclipse. It wasn't meant to be.

Bibliography:

Figure 1.
Eclipse. usage from 2012 to 2016 according to a JRebel survey
. Source.

 Read the full article

ELF Hello World Tutorial / ELF header Updated 2025-07-16

 View more

Running:

readelf -h hello_world.o

outputs:

Magic:   7f 45 4c 46 02 01 01 00 00 00 00 00 00 00 00 00
Class:                             ELF64
Data:                              2's complement, little endian
Version:                           1 (current)
OS/ABI:                            UNIX - System V
ABI Version:                       0
Type:                              REL (Relocatable file)
Machine:                           Advanced Micro Devices X86-64
Version:                           0x1
Entry point address:               0x0
Start of program headers:          0 (bytes into file)
Start of section headers:          64 (bytes into file)
Flags:                             0x0
Size of this header:               64 (bytes)
Size of program headers:           0 (bytes)
Number of program headers:         0
Size of section headers:           64 (bytes)
Number of section headers:         7
Section header string table index: 3

Running:

readelf -h hello_world.out

outputs:

Magic:   7f 45 4c 46 02 01 01 00 00 00 00 00 00 00 00 00
Class:                             ELF64
Data:                              2's complement, little endian
Version:                           1 (current)
OS/ABI:                            UNIX - System V
ABI Version:                       0
Type:                              EXEC (Executable file)
Machine:                           Advanced Micro Devices X86-64
Version:                           0x1
Entry point address:               0x4000b0
Start of program headers:          64 (bytes into file)
Start of section headers:          272 (bytes into file)
Flags:                             0x0
Size of this header:               64 (bytes)
Size of program headers:           56 (bytes)
Number of program headers:         2
Size of section headers:           64 (bytes)
Number of section headers:         6
Section header string table index: 3

Bytes in the object file:

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  |....@.....@.....|

Executable:

00000000  7f 45 4c 46 02 01 01 00  00 00 00 00 00 00 00 00  |.ELF............|
00000010  02 00 3e 00 01 00 00 00  b0 00 40 00 00 00 00 00  |..>.......@.....|
00000020  40 00 00 00 00 00 00 00  10 01 00 00 00 00 00 00  |@...............|
00000030  00 00 00 00 40 00 38 00  02 00 40 00 06 00 03 00  |....@.8...@.....|

Structure represented:

# define EI_NIDENT 16

typedef struct {
    unsigned char   e_ident[EI_NIDENT];
    Elf64_Half      e_type;
    Elf64_Half      e_machine;
    Elf64_Word      e_version;
    Elf64_Addr      e_entry;
    Elf64_Off       e_phoff;
    Elf64_Off       e_shoff;
    Elf64_Word      e_flags;
    Elf64_Half      e_ehsize;
    Elf64_Half      e_phentsize;
    Elf64_Half      e_phnum;
    Elf64_Half      e_shentsize;
    Elf64_Half      e_shnum;
    Elf64_Half      e_shstrndx;
} Elf64_Ehdr;

Manual breakdown:

0 0: EI_MAG = 7f 45 4c 46 = 0x7f 'E', 'L', 'F': ELF magic number
0 4: EI_CLASS = 02 = ELFCLASS64: 64 bit elf
0 5: EI_DATA = 01 = ELFDATA2LSB: little endian data
0 6: EI_VERSION = 01: format version
0 7: EI_OSABI (only in 2003 Update) = 00 = ELFOSABI_NONE: no extensions.
0 8: EI_PAD = 8x 00: reserved bytes. Must be set to 0.
1 0: e_type = 01 00 = 1 (big endian) = ET_REl: relocatable format
On the executable it is 02 00 for ET_EXEC.
Another important possibility for the executable is ET_DYN for PIE executables and shared libraries.
ET_DYN tells the Linux kernel that the code is position independent, and can loaded at a random memory location with ASLR.
This is explained further at:
- stackoverflow.com/questions/2463150/what-is-the-fpie-option-for-position-independent-executables-in-gcc-and-ld/51308031#51308031
- stackoverflow.com/questions/34519521/why-does-gcc-create-a-shared-object-instead-of-an-executable-binary-according-to/55704865#55704865
1 2: e_machine = 3e 00 = 62 = EM_X86_64: AMD64 architecture
1 4: e_version = 01 00 00 00: must be 1
1 8: e_entry = 8x 00: execution address entry point, or 0 if not applicable like for the object file since there is no entry point.
On the executable, it is b0 00 40 00 00 00 00 00. The kernel puts the RIP directly on that value when executing. It can be configured by the linker script or -e. But it will segfault if you set it too low: stackoverflow.com/questions/2187484/why-is-the-elf-execution-entry-point-virtual-address-of-the-form-0x80xxxxx-and-n
2 0: e_phoff = 8x 00: program header table offset, 0 if not present.
40 00 00 00 on the executable, i.e. it starts immediately after the ELF header.
2 8: e_shoff = 40 7x 00 = 0x40: section header table file offset, 0 if not present.
3 0: e_flags = 00 00 00 00 Arch specific. i386 docs say:
The Intel386 architecture defines no flags; so this member contains zero.
3 4: e_ehsize = 40 00: size of this elf header. TODO why this field needed? Isn't the size fixed?
3 6: e_phentsize = 00 00: size of each program header, 0 if not present.
38 00 on executable: it is 56 bytes long
3 8: e_phnum = 00 00: number of program header entries, 0 if not present.
02 00 on executable: there are 2 entries.
3 A: e_shentsize and e_shnum = 40 00 07 00: section header size and number of entries
3 E: e_shstrndx (Section Header STRing iNDeX) = 03 00: index of the .shstrtab section.

 Read the full article

Drug liberalization Updated 2025-07-16

 View more

Ciro Santilli supports full legalization of all drugs, because he feels that it would be better overall for the world to have cheaper drugs and more drug addicts, but way, way less organized crime.

These should be extremely controlled of course, with extremely high taxes that puts their price just below the current illegal market, and a complete ban on any positive advertising.

Ciro believes that maybe the government could even go as far as giving free drugs to drug addicts so they don't have to rob to get a fix.

This is notably considering that drug-led organized crime completely dominates and corrupts the politics of many production and trafficking zones, which are already generally poor fucked up places to start with:

Ciro's experiences in Brazil such as mentioned at São Remo, the favela next to USP, although much less extreme than the above, also come to mind.

Drug traffic corrupts everything. It prevents development of honest people. It is a cancer, which we have failed time and time a gain to cure. The only cure is to accept the other less insidious of addiction.

Bibliography:

How to Fix a Drug Scandal (2020) gives a good sense of the relentlessness of the drug war, and how it affects people who are already poor the most

 Read the full article

Dual space Updated 2025-07-16

 View more

The dual space of a vector space

V

, sometimes denoted

V^{*}

, is the vector space of all linear forms over

V

with the obvious addition and scalar multiplication operations defined.

Since a linear form is completely determined by how it acts on a basis, and since for each basis element it is specified by a scalar, at least in finite dimension, the dimension of the dual space is the same as the

V

, and so they are isomorphic because all vector spaces of the same dimension on a given field are isomorphic, and so the dual is quite a boring concept in the context of finite dimension.

Infinite dimension seems more interesting however, see: en.wikipedia.org/w/index.php?title=Dual_space&oldid=1046421278#Infinite-dimensional_case

One place where duals are different from the non-duals however is when dealing with tensors, because they transform differently than vectors from the base space

V

 Read the full article

Dual vector Updated 2025-07-16

 View more

Dual vectors are the members of a dual space.

In the context of tensors , we use raised indices to refer to members of the dual basis vs the underlying basis:

e_{1} e_{2} e_{3} e^{1} e^{2} e^{3} \in V \in V \in V \in V^{*} \in V^{*} \in V^{*}

(1)

The dual basis vectors

e^{i}

are defined to "pick the corresponding coordinate" out of elements of V. E.g.:

e^{1} (4, - 3, 6) e^{2} (4, - 3, 6) e^{3} (4, - 3, 6) = 4 = - 3 = 6

(2)

By expanding into the basis, we can put this more succinctly with the Kronecker delta as:

e^{i} (e_{j}) = δ_{ij}

(3)

Note that in Einstein notation, the components of a dual vector have lower indices. This works well with the upper case indices of the dual vectors, allowing us to write a dual vector

f

as:

f = f_{i} e^{i}

(4)

In the context of quantum mechanics, the bra notation is also used for dual vectors.

 Read the full article

D-Wave Systems Updated 2025-07-16

 View more

Vaporware?

 Read the full article

Dynamic array Updated 2025-07-16

 Read the full article

E91 Updated 2025-07-16

 View more

Requires entangled particles, unlike BB84 which does not.

 Read the full article

Early Google employee Updated 2025-07-16

 View more

Bibliography:

ChatGPT produces:

Heather Cairns (Employee #4) - Joined in 1998. She handled HR and was one of the earliest administrative hires.
Harry Cheung (Employee #5) - Joined in 1999. An early engineer.
Gerald Aigner (Employee #6) - Hired in 1999. Worked as a software engineer.
Susan Wojcicki (Employee #16) - Joined in 1999. She rented her garage to Larry and Sergey in 1998 and later became an integral part of Google's business and advertising teams.
Marissa Mayer (Employee #20) - Hired in 1999. Played a major role in Google Search and design.