Igor Schein on Tue, 15 Dec 1998 12:14:50 -0500 |
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interesting *randomness* issue |
Hi, I noticed something weird: ? randpol(d,b)=x^d+sum(k=0,d-1,(random(2*b+1)-b)*x^k) ? v=[];for(k=1,2000,t=randpol(8,2);if(polisirreducible(t),polgalois(t),);v=concat(v,[t])) ? matsize(v) [1, 2000] ? length(Set(v)) 816 So first I define a function which returns a random monic polynomial of degree d and absolute value of coefficients <= b Then I generate 2000 random polynomials of degree 8 and run polgalois() on those which are irreducible. From the 4th command it's clear that they're not random anymore. And indeed, if you print the vector v above, you'll see that it hits a loop of length 8 in the end of the first 1000, and loops forever. However, if I use degree 7 polynomials instead, the pseudo-randomness is fine. So I am curious how come polgalois() causes random number generator to go berserk. Thanks Igor