alphaBetaGamma (u/alphaBetaGamma)

alphaBetaGamma commented on “The Assayer” by Galileo Galilei (1623) [pdf] web.stanford.edu/~jsabol/... · Posted by u/sandwichsphinx

griffzhowl · 10 months ago

I don't think Galileo was quite the first to make a telescope. He had heard a description of one by someone in the Netherlands, and then designed and built his own. He was the first to use it to observe and describe those otherwise invisible objects in the night sky though

alphaBetaGamma · 10 months ago

If I remember correctly, in that book Galileo says he heard of someone in the Netherlands having made a microscope, but without any details about how it was made. Armed with the knowledge that something like that was possible, he designs a telescope (lenses only, not a Newton type telescope with a mirror). He build three and used the last and best to do his observations.

alphaBetaGamma commented on “The Assayer” by Galileo Galilei (1623) [pdf] web.stanford.edu/~jsabol/... · Posted by u/sandwichsphinx

alphaBetaGamma · 10 months ago

Galileo refers in this to a book he had published earlier, the "Starry Messenger". It is well worth reading.

Galileo had just build the first ever telescope and he describes what he has discovered: there are incredibly more stars than can be seen by the naked eye; Jupiter has satellites; there are mountains on the moon and he has figured out their height from the length of their shadows... The book is full of the quiet excitement of a man who has discovered a new world, and seen what no man had seen before.

https://archive.org/details/siderealmessenge80gali/page/6/mo...

alphaBetaGamma commented on It Belongs in a Museum: Isabella Stewart Gardner builds a place to house her art laphamsquarterly.org/roun... · Posted by u/prismatic

alphaBetaGamma · 3 years ago

Fun fact: if your first name is Isabella you can visit the museum for free. I believe that she specified this in her will.

alphaBetaGamma commented on Apple acquires classical music streaming service Primephonic apple.com/newsroom/2021/0... · Posted by u/todsacerdoti

hluska · 4 years ago

This is way off topic (and I apologize) but it’s remarkably hard to learn about classical music. Would you do me a favour? I’m a classical neophyte and struggle with composer/orchestra/conductor fit. Can you recommend any combinations that I need to hear??

Thus far, I think I like baroque and Bach makes me happy. I’m starting to think I love opera but I might just have a thing for Maria Callas. However, I’m open to any and all recommendations and will love the hell out of anyone who recommends anything. I prefer vinyl but I’ll buy an 8 track if it helps.

(Whenever I’ve asked HN for help, I’ve ended up with new favourite recordings of all time. Thanks to all the classical music lovers who have really enhanced my life throughout the years.)

alphaBetaGamma · 4 years ago

If you like Bach you might want to learn to listen to polyphony: the form of music in which multiple melodies are played simultaneously while forming an harmonious whole. I recommend looking & listening to videos of Stephen Malinowsky (smalin on youtube), particularly his older videos with less visual clutter. Each color is a separate melody. Initially and you should try to focus on just one melody, then see if you can easily switch your focus to an other one. Then see if you can listen/focus on two melodies at the same time, then three... https://www.youtube.com/playlist?list=PL81D26D4A47388279

In general I would not worry to much about the performer, but it might be interesting to listen to different interpretations of the same piece, particularly from composers with very idiosyncratic styles. On youtube, Ashish Xiangyi Kumar (https://www.youtube.com/c/AshishXiangyiKumar) has videos of pieces (mainly piano solo) interpreted by different artist.

alphaBetaGamma commented on Replace multiple strings, O(1) wrt number of replacements unix.stackexchange.com/a/... · Posted by u/alphaBetaGamma

alphaBetaGamma · 5 years ago

I was using sed to do many replacements (hundreds) in a file and it was starting to be slow, running in O(num_replacemnts). I thought that this can be done with a state machine so the runtime could be independent of the number of replacements.

I googled a bit and found this amazing gem: it uses lex to create a custom C program that does just what you want. Posix compliant. All wrapped up in bash function.

alphaBetaGamma commented on Show HN: Sed to C translator written in sed github.com/lhoursquentin/... · Posted by u/lhoursquentin

ketanmaheshwari · 5 years ago

Nice! In the why part you speculatively mention better speed. Do you have any concrete benchmark results?

If fast, the tool would be very useful for my work where I run an anonimization sed script with hundreds of transformations on millions of lines that takes hours to run.

But even if it is not fast, this is a fun project.

alphaBetaGamma · 5 years ago

Not the author, but I had a similar problem.

If you specify many replacement rules in sed, it will run in O(num_replacements * num_lines). You should be able to use a state machine to do it in O(num_lines), so I google a bit and found this amazing gem: https://unix.stackexchange.com/a/137932

tl;dr: it uses lex to create a custom C program that does "just what you need", compiles it, and runs it on your input. The whole thing wrapped in a bash function. Bonus: it's POSIX compliant.

alphaBetaGamma commented on C64 Memory Map pagetable.com/?p=1397... · Posted by u/ingve

alphaBetaGamma · 5 years ago

If I remember correctly, the system calls where indirect jumps where the address of the jump was in ram (it had been copied from the rom on startup): it was designed to you could hijack system calls and modify their behavior. This blew my mind as a teenager.

I wish modern system where still designed like that...

alphaBetaGamma commented on Gears ciechanow.ski/gears/... · Posted by u/robert-boehnke

alphaBetaGamma · 6 years ago

I have heard that it is good practice to always chose the number of teeth of two gears to be relatively prime. This is because there can be impurities in the metal, and if you have a small part of a tooth that is harder than the rest it will erode the opposing gear (there is always some friction going on). By choosing the number of teeth to be relatively prime, the wear and tear is distributed uniformly on the gears, and thus they last longer.

alphaBetaGamma commented on How and why CPUs do “branch prediction” (2017) danluu.com/branch-predict... · Posted by u/majke

alphaBetaGamma · 6 years ago

In some/many cases there is code before the branch that does not influence the branch condition. In that case, would it be possible to architect the cpu such that it could execute the branch 'early'? I'm thinking of a special asm instruction like 'execute the next 4 instructions, and only then do the conditional jump'.

E.g. instead of:

  i=0
  StartLoop:
  i+=1
  do_stuff_0
  do_stuff_1
  do_stuff_2
  do_stuff_3
  if i<N goto StartLoop

we would have:

  i=0
  StartLoop:
  i+=1
  do_stuff_0
  do_stuff_1
  if i<N goto StartLoop in 2 instructions
  do_stuff_2
  do_stuff_3