mpz_rrandomb most significant bit always set
tg at gmplib.org
Sat Mar 5 17:54:09 UTC 2016
Emmanuel Thomé <emmanuel.thome at gmail.com> writes:
The documentation of mpz_rrandomb says:
-- Function: void mpz_rrandomb (mpz_t ROP, gmp_randstate_t STATE,
Generate a random integer with long strings of zeros and ones in
the binary representation. Useful for testing functions and
algorithms, since this kind of random numbers have proven to be
more likely to trigger corner-case bugs. The random number will
be in the range 0 to 2^N-1, inclusive.
I was surprised to notice that in fact, the most significant bit of
the output seems to be always set, as shown by the code below.
Sure, this behaviour does not *contradict* the documentation, but
perhaps the latter could be changed to reflect this fact, as for
The random number will be in the range 2^(N-1) to 2^N-1, inclusive.
Thanks for spotting this.
I agree with your change, but I think our claim that 0 is included in
the returned numbers is wrong. A less helpful fix would be to remove
the word "inclusive"... :-)
Please encrypt, key id 0xC8601622
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