Was a closed source project by "Roboti LLC", which was then acquired by DeepMind in October 2021 and open sourced March 2022: www.deepmind.com/blog/open-sourcing-mujoco
This library is quite cool. Feel very brutally lean and mean.
Amazon is apparently notorious for having bought off many competitors, many of them just to kill off the competition and clear the way, not to actually reuse them.
youtu.be/tfAhTtBlb2Q?t=849 from Video "Jeff Bezos Revealed by Bloomberg (2015)" clearly shows Tim O'Reilly saying that very clearly about Bezos.Perhaps O'Reilly who is the bookselling business is not the greatest fan of Jeff. But still. My God.
I do know of a number of cases in which he [Bezos] has acquired companies in order to take out competitors, potential future competitors. Rather than because he actually wants that business to continue.
www.yalelawjournal.org/pdf/e.710.Khan.805_zuvfyyeh.pdf Amazon's Antitrust Paradox by Lina M . Khan from The Yale Law Journal raises this incredible issue.
quoteinvestigator.com/2014/02/26/lazy-job/ (archive):
I will always choose a lazy person to do a difficult job because a lazy person will find an easy way to do it.
See also: effortless effort.
Mathematics and Foundations of Computer Science masters course of the University of Oxford Updated 2025-01-10 +Created 1970-01-01
In the standard formulation of Maxwell's equations, the electric current is a convient but magic input.
Would it be possible to use Maxwell's equations to solve a system of pointlike particles such as electrons instead?
The following suggest no, or only for certain subcases less general than Maxwell's equations:
This is the type of thing where the probability aspect of quantum mechanics seems it could "help".
English as a universal language by Dan Dascalescu (2008) Updated 2025-01-10 +Created 1970-01-01
Only appears in the executable.
Contains information of how the executable should be put into the process virtual memory.
The executable is generated from object files by the linker. The main jobs that the linker does are:
- determine which sections of the object files will go into which segments of the executable.In Binutils, this comes down to parsing a linker script, and dealing with a bunch of defaults.You can get the linker script used with
ld --verbose, and set a custom one withld -T. - do relocation according to the
.rela.textsection. This depends on how the multiple sections are put into memory.
readelf -l hello_world.out gives:Elf file type is EXEC (Executable file)
Entry point 0x4000b0
There are 2 program headers, starting at offset 64
Program Headers:
Type Offset VirtAddr PhysAddr
FileSiz MemSiz Flags Align
LOAD 0x0000000000000000 0x0000000000400000 0x0000000000400000
0x00000000000000d7 0x00000000000000d7 R E 200000
LOAD 0x00000000000000d8 0x00000000006000d8 0x00000000006000d8
0x000000000000000d 0x000000000000000d RW 200000
Section to Segment mapping:
Segment Sections...
00 .text
01 .dataOn the ELF header, and:
e_phoff, e_phnum and e_phentsize told us that there are 2 program headers, which start at 0x40 and are 0x38 bytes long each, so they are:00000040 01 00 00 00 05 00 00 00 00 00 00 00 00 00 00 00 |................|
00000050 00 00 40 00 00 00 00 00 00 00 40 00 00 00 00 00 |..@.......@.....|
00000060 d7 00 00 00 00 00 00 00 d7 00 00 00 00 00 00 00 |................|
00000070 00 00 20 00 00 00 00 00 |.. ..... |00000070 01 00 00 00 06 00 00 00 | ........|
00000080 d8 00 00 00 00 00 00 00 d8 00 60 00 00 00 00 00 |..........`.....|
00000090 d8 00 60 00 00 00 00 00 0d 00 00 00 00 00 00 00 |..`.............|
000000a0 0d 00 00 00 00 00 00 00 00 00 20 00 00 00 00 00 |.......... .....|Structure represented www.sco.com/developers/gabi/2003-12-17/ch5.pheader.html:
typedef struct {
Elf64_Word p_type;
Elf64_Word p_flags;
Elf64_Off p_offset;
Elf64_Addr p_vaddr;
Elf64_Addr p_paddr;
Elf64_Xword p_filesz;
Elf64_Xword p_memsz;
Elf64_Xword p_align;
} Elf64_Phdr;Breakdown of the first one:
- 40 0:
p_type=01 00 00 00=PT_LOAD: this is a regular segment that will get loaded in memory. - 40 4:
p_flags=05 00 00 00= execute and read permissions. No write: we cannot modify the text segment. A classic way to do this in C is with string literals: stackoverflow.com/a/30662565/895245 This allows kernels to do certain optimizations, like sharing the segment amongst processes. - 40 8:
p_offset= 8x00TODO: what is this? Standard says:This member gives the offset from the beginning of the file at which the first byte of the segment resides.
But it looks like offsets from the beginning of segments, not file? - 50 0:
p_vaddr=00 00 40 00 00 00 00 00: initial virtual memory address to load this segment to - 50 8:
p_paddr=00 00 40 00 00 00 00 00: unspecified effect. Intended for systems in which physical addressing matters. TODO example? - 60 0:
p_filesz=d7 00 00 00 00 00 00 00: size that the segment occupies in memory. If smaller thanp_memsz, the OS fills it with zeroes to fit when loading the program. This is how BSS data is implemented to save space on executable files. i368 ABI says onPT_LOAD:The bytes from the file are mapped to the beginning of the memory segment. If the segment’s memory size (p_memsz) is larger than the file size (p_filesz), the ‘‘extra’’ bytes are defined to hold the value 0 and to follow the segment’s initialized area. The file size may not be larger than the memory size.
- 60 8:
p_memsz=d7 00 00 00 00 00 00 00: size that the segment occupies in memory - 70 0:
p_align=00 00 20 00 00 00 00 00: 0 or 1 mean no alignment required. TODO why is this required? Why not just usep_addrdirectly, and get that right? Docs also say:p_vaddr should equal p_offset, modulo p_align
The second segment (
.data) is analogous. TODO: why use offset 0x0000d8 and address 0x00000000006000d8? Why not just use 0 and 0x00000000006000d8?Then the:section of the
Section to Segment mapping:readelf tells us that:- 0 is the
.textsegment. Aha, so this is why it is executable, and not writable - 1 is the
.datasegment.
TODO where does this information come from? stackoverflow.com/questions/23018496/section-to-segment-mapping-in-elf-files
x.com/Birdyword/status/1777591446612193667Singaporean taxi drivers are the cutest.
A while ago a Singaporean taxi driver asked me what a UK hawker centre lunch might cost. I explained that there aren't any. He asked what office workers ate, and I explained the concept of Meal deals. And he looked at me with such a powerful combination of pity and revulsion.
MIT 8.06 Quantum Physics III, Spring 2018 by Barton Zwiebach Updated 2025-01-10 +Created 1970-01-01
100 10-20 minute videos properly split by topic, good resource!
Instructor: Barton Zwiebach.
Free material from university courses:
- physics.weber.edu/schroeder/quantum/QuantumBook.pdf (archive) "Notes on Quantum Mechanics" pusbliehd by Daniel V. Schroeder (2019) The author is from from Weber State University.
Electronic Ink such as that found on Amazon Kindle is the greatest invention ever made by man.
Once E Ink reaches reasonable refresh rates to replace liquid crystal displays, the world will finally be saved.
It would allow Ciro Santilli to spend his entire life in front of a screen rather in the real world without getting tired eyes, and even if it is sunny outside.
Ciro stopped reading non-code non-news a while back though, so the current refresh rates are useless, what a shame.
OMG, this is amazing: getfreewrite.com/
Don't like this very much, but if it's the only way...
Maybe focus on job ads like Stack Overflow.
Then:
- like YouTube, pay creators proportionally to views/metrics
- paid subscription to remove ads from site
Unlisted articles are being shown, click here to show only listed articles.