Ciro Santilli @cirosantilli 37

TODO understand.

After something broke on the website due to SQLite vs PostgreSQL inconsistencies and took me a day to figure it out, I finally decided to update the test system so that OURBIGBOOK_POSTGRES=true npm test will run the tests on PostgreSQL.

Originally, these were being run only on SQLite, which is the major use case for OurBigBook CLI, which came before the website.

But the website runs on PostgreSQL, so it is fundamental to test things in PostgreSQL as well.

We know that superfluidity happens more easily in bosons, and so electrons joins in Cooper pairs to form bosons, making a superfluid of Cooper pairs!

Isn't that awesome!

For each process, the virtual address space looks like this:

The kernel maintains a list of pages that belong to each process, and synchronizes that with the paging.

If the program accesses memory that does not belong to it, the kernel handles a page-fault, and decides what to do:

When an ELF file is loaded by the kernel to start a program with the exec system call, the kernel automatically registers text, data, BSS and stack for the program.

The brk and mmap areas can be modified by request of the program through the brk and mmap system calls. But the kernel can also deny the program those areas if there is not enough memory.

brk and mmap can be used to implement malloc, or the so called "heap".

mmap is also used to load dynamically loaded libraries into the program's memory so that it can access and run it.

Stack allocation: stackoverflow.com/questions/17671423/stack-allocation-for-process

Calculating exact addresses Things are complicated by:

Why the text does not start at 0: stackoverflow.com/questions/14795164/why-do-linux-program-text-sections-start-at-0x0804800-and-stack-tops-start-at-0

Minimal example: github.com/cirosantilli/x86-bare-metal-examples/blob/5c672f73884a487414b3e21bd9e579c67cd77621/paging.S

Like everything else in programming, the only way to really understand this is to play with minimal examples.

What makes this a "hard" subject is that the minimal example is large because you need to make your own small OS.

The United Kingdom is a great place to cycle in general as there's plenty of small country roads and interesting new small towns to discover, perhaps much like the rest of Europe, as opposed to the United States, which likely has some huge infinitely long straight roads with a lot of nothing in between.

Of particular interest is the large amount of airfields and small air raid shelters in the fields, an ominous reminder of world war 2. The airfields are in various states, from functional military fields, many converted to civilian usage, some have barely any tarmac left but still see usage. And some were just completely abandoned and decayed and became recreation grounds and farms. The UK is therefore also a great place to be if you want to learn to fly as a hobby!

Good starting point:

Next, you want to decide about nice destinations to reach/go through, and these are good ideas to look into:

Correspond to the angular part of Laplace's equation in spherical coordinates after using separation of variables as shown at: en.wikipedia.org/wiki/Spherical_harmonics#Laplace's_spherical_harmonics

Composed by Wang Huiran in 1960.

The Yi people are one of the 55 Chinese ethnic minorities officially recognized by the Chinese government.

His website is down as of 2020, shame: wiki.dandascalescu.com/essays/english-universal-language

This dude is interesting. Quite crazy type. It is hard to differentiate genius from mad.

Ciro Santilli bumps on his Stack Overflow from time to time: stackoverflow.com/users/1269037/dan-dascalescu.

A superstar security researcher with some major exploits from in the 2000's.

One is reminded of Nick Leeson.

One things must be said: the root cause of all of this is the replication crisis.

This is why he managed to go on for so long.

People felt it was normal to have to try for one or two years to replicate a paper.