On Mon, May 9, 2011 at 8:31 PM, Don <dondod...@gmail.com> wrote:
> That would do it if you have a 64-bit type, which most implementations
> have, but the standard does not require.
> I think that I can make it shorter and cleaner.
>
> int main(int argc, char* argv[])
> {
> const int n=49;
> char a[n]={0};
>
I think we can use a single character like char a=0; instead of array of
characters as ultimately the value is incremented for a[0] only in your
code.
And i was testing with smaller values of n=1 and found something strange
like the value of a[p] increases from 0 to 127 (thats normal) but after
adding 1 to 127 it shows -128..I know that char is of 1byte or 8 bits only
and after +127 its value will overflow.
I have question regarding the same:
1) How to calculate the next value in case of overflow. As i tried
calculating by binary addition and 0111 1111 + 1 = 1000 0000 thats means
answer should have been -0 or 0.
int p=0;
>
> // This line will run for 10^100 years
> for(; p < n; p = ++a[p] ? 0 : p + 1);
>
> return 0;
> }
>
> The array of 49 bytes provides 392 bits of state, which will take more
> than the 2^387 cycles available in a google years.
>
> If the processor takes 9 operations to execute the loop, a value of
> n=48 would be sufficient.
> Don
>
> On May 7, 12:24 pm, Dave <dave_and_da...@juno.com> wrote:
> > @Don: Here is my solution:
> >
> > unsigned long long int a=1;
> > unsigned long long int b=0;
> > unsigned long long int c=0;
> > unsigned long long int d=0;
> > unsigned long long int e=0;
> > unsigned long long int f=0;
> > unsigned long long int g=0;
> > unsigned long long int h=0;
> > /* here is the line "/
> > while(a)if(!++h)if(!++g)if(!++f)if(!++e)if(!++d)if(!++c)if(!++b)++a;
> >
> > My reasoning is as follows: 1 google years ~= 10^116.5 nanoseconds ~=
> > 2^387. Thus, incrementing an integer of length 387 bits once every
> > nanosecond should take a google years to overflow. Seven 64-bit
> > integers provides 448 bits of state.
> >
> > Dave
> >
> > On May 6, 11:25 am, Don <dondod...@gmail.com> wrote:
> >
> > > What is the shortest single line in a C program which will take more
> > > than a google years to execute, but will eventually complete? You are
> > > permitted to have code before or after the line, but execution of the
> > > code must remain on that line, meaning no function calls, etc. Assume
> > > a processor which executes 1 billion operations a second.
> >
> >
>
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--
Aamir Khan
Indian Institute of Technology Roorkee,
Roorkee, Uttarakhand,
India , 247667
Phone: +91 9557647357
email: aami...@iitr.ernet.in <aamir...@iitr.ernet.in>
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