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- Subject: Re: Help with an algorithm
- From: Steve Litt <slitt@...>
- Date: Sat, 25 May 2013 11:33:47 -0400
On Sat, 25 May 2013 14:33:18 +1000
Vaughan McAlley <firstname.lastname@example.org> wrote:
> On 25 May 2013 01:28, Steve Litt <email@example.com> wrote:
> > On Fri, 24 May 2013 17:20:40 +1000
> > 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...
Where in the program did you tell it you're using 40 bit numbers? Or
did you just quit when you reached
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.
Steve Litt * http://www.troubleshooters.com/
Troubleshooting Training * Human Performance