Re: [Boost-users] random number generator 160 bit.
From: "chun ping wang"
[code skipped] T n(Random::randint<T>(numeric_cast<T>(pow(2.0, num_digits - 1)), numeric_cast<T>(pow(2.0, num_digits))) [code skipped]
now num_digits is number of bits. If i pass 160 bit as like for DSA algorithm the program crashes. I pass 8 and it works, how come? Is there a better way to do this? Oh f is any function that can deteremine if a number is most likely a prime or not....
My guess is that numeric_cast<T>(pow(2.0, num_digits)) throws an overflow exception. I don't know what you're using for T, but obviously even a long long can't hold a 160-bit integer (at least not on any architecture I'm aware of). To verify this, catch on overflow_error and see if this prevents the crash. - James Jones Administrative Data Mgmt. Webmaster 375 Raritan Center Pkwy, Suite A Data Architect Edison, NJ 08837
yeah i get this error. bad numeric conversion: positive overflow Still i
need some way to generate a 160 bit integer somehow. ... :(
On 8/9/06, james.jones@firstinvestors.com
From: "chun ping wang"
[code skipped] T n(Random::randint<T>(numeric_cast<T>(pow(2.0, num_digits - 1)), numeric_cast<T>(pow(2.0, num_digits))) [code skipped]
now num_digits is number of bits. If i pass 160 bit as like for DSA algorithm the program crashes. I pass 8 and it works, how come? Is there a better way to do this? Oh f is any function that can deteremine if a number is most likely a prime or not....
My guess is that numeric_cast<T>(pow(2.0, num_digits)) throws an overflow exception. I don't know what you're using for T, but obviously even a long long can't hold a 160-bit integer (at least not on any architecture I'm aware of).
To verify this, catch on overflow_error and see if this prevents the crash.
- James Jones Administrative Data Mgmt. Webmaster 375 Raritan Center Pkwy, Suite A Data Architect Edison, NJ 08837 _______________________________________________ Boost-users mailing list Boost-users@lists.boost.org http://lists.boost.org/mailman/listinfo.cgi/boost-users
chun ping wang wrote:
yeah i get this error. bad numeric conversion: positive overflow Still i need some way to generate a 160 bit integer somehow. ... :(
Just generate 5 unsigned integers of 32bit size. Of course, there's no built-in data type capable of holding so many bits, but you could put the uint's into a continues array and treat the array as one big number. Stephan
participants (3)
-
chun ping wang -
james.jones＠firstinvestors.com -
Stephan Tolksdorf