RandomScoreFunction.PRNG generates weak random numbers

[jpountz]

Here is some code extracted from PRNG.random(int):

long rand = doc;
rand |= rand << 32;
rand ^= rand;
return nextFloat(rand);

The issue is that rand ^= rand; is equivalent to rand = 0; so in the end, the random score generation completely discards the doc ID that was provided.

[pickypg]

Note: this is a dupe of #5454 although this one explains the issue

[uboness]

closed by e8ea9d7