Ed S @EdS@mastodon.sdf.org

things i have learned while figuring out how to implement floating point on the Z80:

fast division (ie multiplying by reciprocal) is only fast if multiplication is much faster than slow division. if you have to do 3 multiplies in the course of it and your multiplies turn out to be 1000 cycles each, long division taking 1800 cycles starts to look pretty damn good

if possible, do slow division with the whole divisor at once. for much the same reason: trying to piece together a 64/32 divide from a 32/16 divide is slow unless you have 32/16 divide instruction, even if you're Roedy Green; it's much easier to make a 48/24 divide from a 32/24 divide

everything gets horrible unless you can fit everything into a single bank of Z80 registers - so 24x8→32 and 32/24→8r24 are probably optimal

you'll feel much better about Z80 cycle times if you divide them by 3½ - assuming an even balance between opcode reads (4 cycles) and data memory accesses (3 cycles); that sort of makes them comparable with 6502 cycle times

Entering week 3 of isolation, my 3yo spontaneously builds an enclosed structure with no doors or windows

RT @MikaelThalen@twitter.activitypub.actor
This shows the location data of phones that were on a Florida beach during Spring Break. It then shows where those phones traveled.

First thing you should note is the importance of social distancing. The second is how much data your phone gives off.

New entry!
A catalogue of mathematical formulas involving π, with analysis
Article by David H. Bailey
In collections: Basically computer science, History, Lists and catalogues
This paper presents a catalogue of mathematical formulas and iterative algorithms for evaluating the mathematical constant π, ranging from Archimedes’ 2200-year-old iteration to some formulas that were discovered only in the past few decades. Computer...
URL: https://www.davidhbailey.com/dhbpapers/pi-formulas.pdf
Entry: https://read.somethingorotherwhatever.com/entry/ACatalogueOfMathematicalFormulasInvolvingPiWithAnalysis

RIGHT 3 eps of 'nairn across britain' are available on iPlayer now! if anyone knows anything about me, this is *the* voice I've aped for years. www.bbc.co.uk/iplayer/episode/p01rn270 via @bbciplayer

Ursula K Le Guin, on tech workers:
"Real power goes to waste. Every wizard uses his art against the others, serving the men of greed. What good can any art be used that way? It's wasted. It goes wrong, or it's thrown away. Like slaves' lives. Nobody can be free alone. Not even a mage. All of them working their magic in prison cells, to gain nothing. There's no way to use power for good."
- "The Finder", from "Tales from Earthsea"

This crisis will play out *identically* whether you check the news every 2-3 days or every 10 minutes. Whether you know every reckless thing every faraway powerful person did, or not.

What can you do to make YOUR life, and the life of those within your reach, a little better?

For a break from the events swirling around us. I've really enjoyed Fabien Sanglard's series writing about ports of "Another World" to various platforms. I find it somehow relaxing. The latest is on the Jaguar:

http://fabiensanglard.net/another_world_polygons_Jaguar/index.html

The others can be found on the home page:

http://fabiensanglard.net/

I never played the game (I saw people playing it in college), but Sanglard's writing about it definitely made me appreciate the work behind it. I want to boot an emulator and play it sometime.

a map of polish cities with 'owo' at the end of their name

I'm going to post a long thread on how to cope better if you're stuck indoors at the moment. I've been housebound by disability for a long while now, and sporadically housebound due to depression and agoraphobia before that. These are things that have improved how I deal with that. This is not gonna make houseboundness painless for you but it might help you cope. Disabled comrades are welcome to share their own advice to this thread.

*This* is the only #Electron I'm interested in!

"Okay, here's the scenario. You are a crew member on a starship."
"Cool."
"Space travel is slow, you'll be stuck with your crewmates a long time."
"So we must get along."
"Yes. Communicate, listen, share limited resources."
"I can do that. What's the starship called?"
"Earth."
#MicroFiction #TootFic #SmallStories

In the 1980s, a group of young dissidents in San Francisco's financial district got together to create a #Zine

"Processed World" is now available at the Internet Archive. Brace yourself for a world of subversive commentary and #Cyberpunk

https://archive.org/details/processedworld

Got an old Pascal S compiler to compile and run under RISC OS. Then I read about Pascal S on the web (the compiler helpfully includes no documentation) and discover that Pascal S is a toy subset of Pascal. No pointers, no file IO, or function parameters...

No wonder nobody bothered recompiling it for 32bit RISC OS....

But that's OK because I learned a little about the history of Pascal. And about the .... unique architecture of the CDC6600.

#riscos #pascal #cdc6600

My math-teaching brother's wish is that 2020 is the year everyone learns that "exponential" doesn't mean "very fast" it means "imperceptibly gradual and then suddenly overwhelming".