Happy Pi Day!

[Tallpine]

I use that when I'm doing my moon shuttle gig.  It helps cut down on the course corrections.

 

It's one of those things you need as a programmer if you find yourself working on a small system (like embedded stuff) where the cost of implemented floating point math is just too great, either in extra circuitry or in extra memory.  Under conditions where the programmer is confined to using fixed-point (scaled integer) math, calculations involving transcendental numbers can still be done using integer multiply/divide sequences.  Need the area for a circle?  Have radius?  It's a simple matter to perform the integer multiplication:  V = R x R x 355, and then the integer divide A = V / 113.

People using computers running modern CPUs and floating-point co-processors don't worry about stuff like this.  People writing for 8-bit and 16-bit embedded processors have to pay attention to these things.

Yes, there are still systems that use low-end (inexpensive) processors, and you'd be amazed at the performance you can get from an 8051 or 6809 running at 12MHz if it's not running Windows or some other heavyweight OS.

#define pi 355/113;

 


Yeah, a lot of people don't realize that many aircraft systems are still 8 or 16 bit.

[seeker_two]

Yesterday, I ate cake.....

Today, I ate pie.....


.....I don't like people telling me when I can eat pie.....

[Phantom Warrior]

*Goes to white board*

*Writes*

Pairs of first three odd numbers	...	113355
Split into two three-digit groups	...	113 _ 355
Swap the two groups, like so	...	355 _ 113
Write as ratio	...	355/113
Enjoy six digits of accuracy	...	3.14159292
[Real pi]	...	3.14159265359

Many years ago (like 1983 or 1984) I read one of the FORTH programming books, which had a cool table of rational approximations of various useful constants (like e, pi, and so on), and this very compact "rational pi" was one of them.

The next rational approximation which is more accurate involves memorizing two 5-digit numbers having no apparent relation to one another.  The 113355 --> 113 355 --> 355 113 --> 355/113 sequence is an easy mnemonic, so in my book it's a keeper.

Enjoy.

This is literally one of the best things I've seen in a while.  It is now my Facebook status and I definitely told people about it today.

[Boomhauer]

This is literally one of the best things I've seen in a while.  It is now my Facebook status and I definitely told people about it today.

Do people just look at you when you tell them stuff like that, nod and slowly back away?

[Tallpine]

Do people just look at you when you tell them stuff like that, nod and slowly back away?

That sounds like a good technique to me 

[MrsSmith]

My eyes glazed over by the time I got to "Enjoy six digits of accuracy ...."

[Boomhauer]

Hey jackwagons, I got pie today! Sweet tater pie.

[lupinus]

Hey jackwagons, I got pie today! Sweet tater pie.

Mmmm sweet taters pie.

[Fly320s]

#define pi 355/113;

 


Yeah, a lot of people don't realize that many aircraft systems are still 8 or 16 bit.

I think the Airbus is 4 bit. And that is on a good day.

[Scout26]

We had harvest apple pie last night. 

[Tallpine]

I think the Airbus is 4 bit. And that is on a good day.

If I recall correctly from working on the A400, the ARINC system is 32 bit, which as you probably know actually only contains about 16 bits of data.  The rest is labeling, parity, etc.