Re: Help with an algorithm

[Steve Litt <slitt@...>]

On Sat, 25 May 2013 14:33:18 +1000
Vaughan McAlley <vaughan@mcalley.net.au> wrote:

> On 25 May 2013 01:28, Steve Litt <slitt@troubleshooters.com> wrote:
> > On Fri, 24 May 2013 17:20:40 +1000

[clip]

> > One comment about all the algorithms delivering the next number
> > with Y number of 1's: I'm pretty sure those work on the natural
> > hardware size of numbers on a given computer, so unless your
> > hardware has 40 bit integers, I don't think those will work, at
> > least not without some modification.
> >
> > One more thing -- make sure your computer has plenty of cooling
> > capacity. My prime number generator got my CPU up to 86 Celsius in
> > maybe 5 minutes.
> >
> > SteveT
> >
> > Steve Litt                *  http://www.troubleshooters.com/
> > Troubleshooting Training  *  Human Performance
> >
> 
> In the end I used the snoob function from
> http://www.hackersdelight.org/basics2.pdf adapted like this:
> 
> unsigned long snoob(unsigned long x)
> {
>     unsigned long smallest, ripple, ones;
> 
>     smallest = x & -x;
>     ripple = x + smallest;
>     ones = x ^ ripple;
>     ones = (ones >> 2)/smallest;
>     return ripple | ones;
> }
> 
> I got over my fear of Xcode (the Raspberry Pi is only 32 bits so would
> have taken much longer), and my iMac chugged through the 40 billion
> numbers in a few hours. Luckily I wasn’t trying to store all the
> numbers, just find the most interesting.
> 
> Working with 64-bit numbers is a bit trickier than 32-bit numbers...
> 
> Vaughan

Vaughan,

Where in the program did you tell it you're using 40 bit numbers? Or
did you just quit when you reached

0000000000000000000000000000000000000001111111111111110000000000000000000000000 

?

Did you find any evidence of your computer CPU overheating?

What properties made some of these numbers more interesting than
others? Did you use pipes like:

./find_fifteens | ./show_interesting.sh > interesting_numbers.txt

These are the times I love computers. I might do this myself.

Thanks,

SteveT

Steve Litt                *  http://www.troubleshooters.com/
Troubleshooting Training  *  Human Performance