2008-12-30, 22:24 | #1 |
Oct 2008
California
236_{10} Posts |
coding midlet for TF
I finished the "powering algorithm" (described on the math page of GIMPS) , any suggestions for improvements in speed/size?
Code:
public boolean testFactor(int expo,int factor){ String n=Integer.toBinaryString(expo); //the binary representation long temp=1; do{ temp*=temp; //square temp<<=Integer.parseInt(n.substring(0,1)); //if the top bit is 1, multiply by 2 temp%=factor; //mod <the test factor> }while((n=n.substring(1)).length()>0); //remove the top bit, and continue if there is still more to do return (temp==1)?true:false; //if the final result is 1, then the test factor was a factor! } Last fiddled with by starrynte on 2008-12-30 at 22:25 |
2008-12-30, 22:31 | #2 |
"Robert Gerbicz"
Oct 2005
Hungary
3·523 Posts |
Use sliding windows. (In gmp it is already implemented, see it's source.)
Last fiddled with by R. Gerbicz on 2008-12-30 at 22:32 |
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