hi,
Have a few doubts on k-distribution. Definition: A pseudo random sequence X(suffix i) of w bit integers of period P satisfying the following condition is said to be k distributed to v bit accuracy:let trunc(x) denote the number formed by the leading v bits of x and consider P of the kv-bit vector (trunc(x(suffix i),trunc(x(suffix(i+1),...,trunc(x(suffix(i+k-1))where (0<=i<P). then each of the 2^(kv) possible combinations of bits occur the same number of times in a period,except for the all-zero combinations that occur once less often. For each v=1,2,..,w let k(v) denote the maximum number such that the sequence os k(v)-distributed to v bit accuracy. Now eg: consider w to be a 4 bit integer,let the i th,(i+1)th, (i+2)nd and (i+3)rd integer be,here we started with i=12 of a maximum period lsfr of period 15. 0001 1000 1100 1110 Taking v=3 bit accuracy,the 3 leading bits are 000 100 110 111 In the example k=3 and v=3 So according to definition there are 2^(kv) possible combinations of bits occur the same number of times in a period. i.e 2^(3*3)=512 combinations. But where are the 512 combinations. We are choosing 3 bits out of 4 bits hence C(4,3)=4!/(3!*1!)=4 There are k=4,hence total combinations arising is only 4*4=16. where did i go wrong? Also why is k-distribution considered as a strong test for randomness? Thanx. Regards Sarath. __________________________________________________ Do you Yahoo!? Yahoo! Web Hosting - establish your business online http://webhosting.yahoo.com
